Dissertations / Theses: 'Admixture(concrete)'

1

Millard, Marcus J. "Effects of Lithium Nitrate Admixture on Early Age Concrete Behavior." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11615.

Full text

Abstract:

Alkali silica reaction (ASR), a reaction which occurs between reactive siliceous mineral components in the aggregate and the alkaline pore solution in concrete, is responsible for substantial damage to concrete structures in the U. S. and across the world. Lithium admixtures, including lithium nitrate (LiNO3), have been demonstrated to mitigate ASR damage, and are of particular interest for use in concrete airfield pavement construction, where ASR damage has been recently linked to the use of certain de-icing chemicals. Although the effectiveness of lithium admixtures at ASR-mitigation is well-researched, relatively less is known regarding the potential effects, including negative effects, on overall concrete behavior. The goal of this research is to better understand the influence of LiNO3 admixture on early age concrete behavior, and to determine if a maximum dosage rate for its use exists. Isothermal calorimetry, rheology and bleed water testing, time of setting, chemical shrinkage, autogenous shrinkage, free and restrained concrete shrinkage, and compressive and flexural strength were measured for pastes and concretes prepared with a range of LiNO3 dosages (i.e., 0, 50, 100, 200, and 400% of the recommended dosage). In addition, the interaction of LiNO3 with cement was evaluated by comparing results obtained with six cements of varying alkali and tricalcium aluminate (C3A) contents. Additionally, one of these cements, was examined alone and with 20% by weight Class F fly ash replacement. Results indicate that the hydration of the tricalcium silicate and tricalcium aluminate components of cement are accelerated by the use of LiNO3, and that low alkali cements (typically specified to avoid damage by ASR) may be particularly susceptible to this acceleration. However, inclusion of Class F fly ash at 20% by weight replacement of cement (also common in applications where ASR is a concern) appears to diminish these possibly negative effects of LiNO3 on early age hydration acceleration and heat generation. Dosages higher than the current standard dosage of LiNO3 may have minor effects on fresh concrete workability, causing slight decreases in Bingham yield stress, corresponding to slightly higher slump. Fresh concrete viscosity may also be affected, though more research is necessary to confirm this effect. LiNO3 had no effect on quantity of bleed water in the mixes tested. Generally, LiNO3 had no effect on initial and final setting times, although increasing dosages caused faster set times in the lowest alkali (Na2Oeq = 0.295%) cement examined. In shrinkage testing, higher LiNO3 dosages appeared to cause initial expansion in some sealed paste specimens, but in all cases the highest dosage led to greater autogenous shrinkage after 40 days. In concrete specimens, however, the restraining effect of aggregates diminished shrinkage, and no effect of the LiNO3 was apparent. In no cases, with any dosage of lithium tested, with or without fly ash replacement, did restrained shrinkage specimens show any cracking. Strength testing produced mixed results, with laboratory specimens increasing in 28-day compressive strength, but companion specimens cast in the field and tested by an outside laboratory, exhibited lower 28-day compressive strength, with increasing lithium dosages. Flexural specimens, also cast in the field and tested by an outside laboratory, appeared to show an increase in 28-day flexural strength with increasing lithium dosages. However, because of the conflicting results when comparing the various strength data, further research is necessary for conclusive evidence of LiNO3 effects on concrete strength.

APA, Harvard, Vancouver, ISO, and other styles

2

SULAIMAN, SALMAN OLUWATOYIN. "FREEZE-THAW DURABILITY OF CONCRETE WITH NATURAL AND RECYCLED CONCRETE AGGREGATES USING AIR ENTRAINING ADMIXTURE." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/1864.

Full text

Abstract:

Freezing and thawing cycles is one of the most damaging factors that affect the durability of concrete. The damages caused by the cyclic freeze-thaw action can be divided into two factors. The first factor is an increase in internal crack, which causes the loss in relative dynamic modulus (RDM) of the concrete and the second factor is surface scaling, which leads to weight loss of the concrete. In this study, the durability of concrete made by replacing natural coarse aggregates (NCA) with various percentages of recycled concrete aggregates (RCA). Also some tests have been conducted with the addition of air entraining admixture (AEA). Prior to mixing the concrete, both NCA and RCA were characterized to determine their suitability as a construction material. Concrete mixes consisting of 0, 20, 40, 60, 80, and 100% replacement (by weight) of NCA with RCA were prepared. The same concrete mixes were prepared again but with the addition of an air entraining admixtures (AEA). All specimens were tested for compressive strength after a curing period of 7, 14, and 28 days. The compressive strength of the concrete made with different percentage of RCA decreases as the percentage of RCA increases. After 28 days of curing, samples with 0, 40, and 100% replacement of NCA with RCA were placed in the freeze-thaw chamber along with 0, 20, 40, 60, 80, and 100% NCA replacement containing AEA. After several cycles of freezing and thawing; the RDM, change in weight and change in length were measured. In this study loss of RDM and weight loss were noticed, as the cyclic freeze-thaw increases. It has also been observed that concrete mixes containing AEA were still durable after 300 cycles of freezing and thawing; however, the specimens without AEA failed before 150 cycles.

APA, Harvard, Vancouver, ISO, and other styles

3

Tatli, Emre. "Pretreatment Of Peanut Shells For Co-production Of Glucose And Concrete Admixture." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615535/index.pdf.

Full text

Abstract:

This thesis work aims the ionic liquid pretreatment of peanut shells for co-production of glucose as fermentable sugar and lignin, considering a multi product perspective. The effects of ionic liquid type and pretreatment time period on the sugar and lignin yields were investigated, as the particle size and temperature parameters were determined in the preliminary studies. Peanut shells were pretreated at constant temperature, 150 oC, for 5, 15 and 30 minutes with 1-ethyl-3-methylimidazolium acetate and for 15, 30 and 60 minutes with 1-ethyl-3-methylimidazolium chloride. The pretreated peanut shells were then subjected to enzymatic hydrolysis in order to produce fermentable sugars, mostly, glucose. The solid residue obtained upon enzymatic hydrolysis was analyzed in terms of lignin quantity. 1-ethyl-3-methylimidazolium acetate pretreatment for 15 minutes resulted in the maximum reducing sugar and lignin yields
28 g of reducing sugar and 20 g of solid residue with 70% lignin were obtained per 100 g of peanut shells. Higher pretreatment time resulted in lower yields. Moreover, no optimal time period for 1-ethyl-3- methylimidazolium chloride pretreatment was obtained, since reducing sugar and lignin yields increased as the time period increased. Also all reducing sugar and lignin yields were lower than that obtained with 1-ethyl-3-methylimidazolium acetate. Lignin obtained upon enzymatic hydrolysis of 1-ethyl-3-methylimidazolium acetate pretreated peanut shells were characterized by SEM, FTIR, TGA and XRD analyses, which also showed the morphological and structural effects of pretreatment and enzymatic hydrolysis on peanut shells
and used as concrete admixture, which increased the flow of the concrete by 6%.

APA, Harvard, Vancouver, ISO, and other styles

4

Al, Menhosh A. A. A. Z. "An experimental study of high-performance concrete using metakaolin additive and polymer admixture." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/45085/.

Full text

Abstract:

In recent years, there has been a growing interest in the use of supplementary cementing materials and polymers to produce high-performance concrete. Utilizing a mineral substance as cement replacement in concrete has less environmental pollution and greatly increases the service life of the concrete structures due to improve the most of concrete properties in compared with conventional concrete. The aim of this project is an experimental study of high-performance concrete using metakaolin (MK) additive as partial replacement of cement and addition of the Styrene-Butadiene rubber (SBR) and Polyvinyl acetate (PVA), to conduct a novel research to investigate the effectiveness of the additives materials on the performance of concrete. It also investigates the effect of additional recycled plastic and glass fibre as reinforcements used in the modified concrete. Firstly, trial mixes of 460 cubes, 24 cylinders and 30 prisms were made to study the setting time, workability, mechanical properties and water absorption of the concrete to find the optimum metakaolin to cement ratio (MK/C), polymer to cement ratio (P/C), water to cement ratio (W/C), and the best curing method among the wet, dry and moist, respectively. The designed concrete mixes have a certain cement/sand/gravel proportion of 1:1.5:3. The trial mixtures were tested for setting time, slump of fresh concrete mix, mechanical properties, including compressive, splitting and flexural strength, and water absorption capacity at age up to 28 days. Three polymers to cement ratios, which are 2.5, 5 and 7.5%, and five metakaolin replacement ratio for the cement, which are 10, 15, 20, 30 and 40%, were studied, respectively. For these mixtures, five W/C ratios, which are 0.35, 0.38, 0.40, 0.45, and 0.50, respectively, were compared. The use of recycled plastic and glass fibre reinforcements took 5% of the total cement weight and tested for splitting and flexural strength testes. The first phase work has shown clear improvement of the performance of concrete modified by partial replacement of cement by metakaolin and adding polymers admixture together. The optimised mix was identified to be that of 5% added polymers included 80% SBR and 20% PVA, 15% metakaolin replacement for cement, 0.45 W/C ratio, and using limestone aggregate as a coarse aggregates and using moist curing method as a curing condition for the concrete. Secondly, the optimum mixture identified in the trial study was further investigated for its mechanical including compressive, flexural, and deformable proprieties at prolonged ages up to 545 days. In addition, a specific durability properties of concrete including water and gas permeability, carbonation penetration, chloride penetration, chemical attack resistance, water absorption, rate of water absorption and the corrosion rate of the steel reinforcement in the concrete. The results show that significant improvement in mechanical properties including compressive, splitting, flexural strength and deformation properties. Also, the results show improvement in durability properties including chemical resistance, water absorption, rate of water absorption, carbonation depth of penetration, chloride ion penetration, water penetration under pressure, water permeability, gas penetration and steel corrosion resistance. The optimum mix of 15% partial replacement of cement by metakaolin, 5% polymer, 0.45 W/C ratio and moist curing condition of the modified concrete produced high-performance concrete more environmental friendly due to improved overall of the mechanical and durability properties of the concrete. Finally, microscopic composition of the hydration products and the corresponding pores structure have been investigated for the optimised mixes based on the material composition analysis and microscopic images obtained using scanning electronic microscope (SEM) and the computed tomography scanner (CT) technologies. Correlation between the mechanical, durability properties and the microscopic phases has been investigated and discussed for a deep understanding of the mechanism of the optimum mixture. SEM and CT scanner technologies provide qualitative and quantitative description of the concrete properties. It’s also, proved that the concrete modified by both of metakaolin and two types of polymers have a significant change in the pores structure of concrete compared with other mixes. Scanning electron microscopy and computed tomography scanner results show that the approach can be effectively applied in high-performance concrete related studies and provide further evidence on mechanical and durability properties of concrete.

APA, Harvard, Vancouver, ISO, and other styles

5

Yazan, Kazim. "Effects Of Retempering With Superplasticizer On Properties Of Prolonged Mixed Mineral Admixture Containing Concrete At Hot Weather Conditions." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606751/index.pdf.

Full text

Abstract:

Concrete which is manufactured in a mixing plant to be delivered to construction site in unhardened and plastic stage is called ready-mixed concrete. Because of technical and economical reasons, many mineral and chemical admixtures are used in ready-mixed concrete production. As a result of extra mixing and delayed placing of ready-mixed concrete (especially at hot weather conditions), there can be many problems about concrete, like slump loss. Addition of water for retempering concrete is the usual procedure, but addition of water without proper adjustment in mixture proportions, adversely affects compressive strength. During this study, effects of prolonged mixing and retempering with superplasticizer on properties of fresh and hardened concrete at hot weather conditions are observed. Some of the properties of concrete inspected are compressive strength, splitting tensile strength, slump and air content. All mixes contain air entrainer and water reducer at a standard amount. The difference between mixes comes from kind and amount of mineral admixture which cement is replaced by. During the study, fly ash, blast furnace slag, ground clay brick and natural pozzolan are used at amounts, 25% and 50% of cement. Also, a mixture of pure cement is prepared as control concrete. 15 cm initial slump is planned in the experimental work. After five minutes and at the end of first, second, third and fourth hours of mixing process, if needed retempering process is proceeded with superplasticizer and samples are taken. As a result of retempering with superplasticizer, the aimed slump values are obtained. The effects are than, observed. As a result of this study, it has been observed that replacing Portland cement with certain mineral admixtures, especially fly ash at certain amounts, can be a solution for slump loss problem, by retarding the slump loss effect of prolonged mixing. Also it has been seen that ground clay brick causes better performance for slump values at lateral stages of mixing with respect to pure Portland cement. Another important observation has been about the increase in the amount of air caused by air entraining admixtures in fresh concrete based on prolonged mixing at hot weather conditions.

APA, Harvard, Vancouver, ISO, and other styles

6

Justice, Joy Melissa. "Evaluation of Metakaolins for Use as Supplementary Cementitious Materials." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6936.

Full text

Abstract:

Two metakaolins were evaluated for use as supplementary cementitious materials in cement-based systems. The metakaolins varied in their surface area (11.1 v. 25.4 m2/g), but were quite similar in mineralogical composition. Performance of metakaolin mixtures was compared to control mixtures and to mixtures incorporating silica fume as partial replacement for cement at water-to-cementitious materials ratios of 0.40, 0.50, and 0.60. In this study, the early age properties of fresh concrete and the mechanical and durability properties of hardened concrete were examined. Early age evaluations aimed to determine the reactivity of metakaolin (heat of hydration) and its effect on mixture workability (slump, setting time, unit weight). In addition, three types of shrinkage were monitored in metakaolin-cement systems: chemical, autogenous, and free. Compressive, tensile, and flexural strength and elastic modulus were measured at various concrete ages. The influence of metakaolin addition on durability was assessed through accelerated testing for sulfate resistance, expansion due to alkali-silica reaction, and through rapid chloride permeability measurements. To further quantify the underlying mechanisms of metakaolin's action, the microstructure of pastes was examined. Calcium hydroxide (CH) content was determined using thermogravimetric analysis and verified using differential thermal analysis. Surface area and pore size distribution were evaluated via nitrogen adsorption. These analyses yielded information about the pozzolanic reactivity of metakaolin, associated CH consumption and pore structure refinement, and resulting improvements in mechanical performance and durability of metakaolin-concretes.

APA, Harvard, Vancouver, ISO, and other styles

7

Adjoudj, Mhamed. "Effet des additions minérales et organiques sur le comportement rhéologique du béton." Thesis, Cergy-Pontoise, 2015. http://www.theses.fr/2015CERG0784/document.

Full text

Abstract:

L'emploi de certaines additions minérales et organiques dans la confection du mortier et du béton contribue à une modification du processus d'hydratation du ciment. L'incorporation de ces additions minérales entraîne également une modification de la distribution granulaire, l'apparition de nouveaux sites de nucléation et une nouvelle activité des surfaces des grains. Ceci nécessite le malaxage avec des superplastifiants qui viennent défloculer les grains, libérer l'eau piégée dans les interstices et améliorer l'ouvrabilité du béton. Ces modifications des propriétés physicochimiques des composants du béton affectent directement les propriétés rhéologiques du mortier et du béton à l'état frais ainsi que ses composantes finales.L'objectif principal de ce travail est focalisé sur la prédiction des modifications rhéologiques apportées par les additions minérales aux mortiers afin de trouver les meilleures compositions d'une mise en œuvre convenable. Une étude expérimentale est entamée sur des mortiers normalisés où le ciment ordinaire est substitué partiellement par différentes additions minérales telles que la fumée de silice, le laitier des hauts fourneaux, la pouzzolane naturelle et le calcaire. Avec l'eau de gâchage, on a ajouté plusieurs types de superplastifiants avec différents dosages où les paramètres rhéologiques du mortier ont été mesurés respectivement par un mini cône et un rhéomètre.Les paramètre rhéologiques obtenus varient sensiblement avec chaque type d'addition minérale et dépendent de ses propriétés et son interaction avec le superplastifiant et les grains de ciment. Le superplastifiant à base de polycarboxylates est plus efficace en présence du ciment contenant du calcaire ou du laitier conduisant à une amélioration des propriétés rhéologiques. Par contre, le mortier devient plus visqueux s'il contient un fort pourcentage de pouzzolane naturelle. Une relation mathématique est proposée qui exprime la variation de chaque paramètre rhéologique selon le taux de substitution du ciment et le dosage en superplastifiant. Cette relation est exprimée par le produit de trois paramètres; l'effet de l'addition minérale, l'effet du superplastifiant et l'effet de leur interaction. Les coefficients de corrélation trouvés sont proches de l'unité et justifient bien la convenance de ce choix. L'application de cette nouvelle relation à d'autres résultats trouvés par d'autres chercheurs présente une grande satisfaction avec des résultats satisfaisant et des coefficients de corrélation allant 0,9 à 0,98
The use of some organic and inorganic admixtures in the production of mortar and concrete contributes to a change in the cement hydration process. The incorporation of these mineral additions also causes a change in the grain distribution, the appearance of new nucleation sites and a new activity of the grain surfaces. This requires mixing with superplasticizers which deflocculates grains, releases the trapped water in the interstices and improves the workability of concrete. These changes in the physicochemical properties of the cement paste directly affect the rheological properties of mortar and concrete in the fresh state and its final components.The main objective of this work is focused on the prediction of rheological changes of mineral additions mortars and finds the best composition for a suitable casting. An experimental study is underway on standardized mortars where ordinary cement is partially substituted by different mineral additions such as silica fume, blast furnace slag, natural pouzzolan and limestone powder. With the mixing water, was added several types with different dosages of superplasticizers where the rheological parameters of the mortar were measured respectively by a rheometer apparatus and a mini cone test.The Theological parameters obtained vary with each type of mineral addition and depend on its properties and its interaction with the superplasticizer and cement grains. The polycarboxylate superplasticizer is more effective in the presence of limestone powder or cement containing slag resulting in improved rheological properties. However, the mortar becomes more viscous if it contains a high percentage of natural pozzolan. A mathematical relationship is provided which expresses the variation of each rheological parameter according the substitution rate of the cement and superplasticizer dosage. This relationship is expressed by the product of three parameters; the effect of the mineral addition, the effect of the superplasticizer and the effect of their interaction. The correlation coefficients found are close to unity and well justify the appropriateness of this choice. The application of this new relationship to other results found by other researchers has high satisfaction with satisfactory results and correlation coefficients ranging from 0.9 to 0.98

APA, Harvard, Vancouver, ISO, and other styles

8

Láznička, Josef. "Studium vlivů ovlivňujících životnost cementobetonových krytů v ČR." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392354.

Full text

Abstract:

This thesis deals with the study of cement – concrete coverings. The aim of the thesis is a summary of current knowledge of these constructions. The experimental part of this paper deals with the design of concrete for the lower layer of cement – concrete cover. Emphasis is placed on the elimination of microcracks and to increase the lifetime of these construction.

APA, Harvard, Vancouver, ISO, and other styles

9

Černá, Hana. "Sledování vlivu složení betonu na odolnost proti abrazi." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392338.

Full text

Abstract:

This diploma thesis focuses on the resistance of concrete to abrasion with regard to the raw materials used for their production. In the theoretical part of the thesis are described admixtures, different types of aggregate and aggregate composition which influence the resistance of concrete to abrasion. In the experimental part, 15 different C30 / 37, S4 concrete formulations were proposed. Different types of aggregates - fecal gravel (Žabčice), biotic granodiorite (Olbramovice) and amphibolite (Želešice) have always been used in the recipes. Fine ground limestone, micro-silica, high-temperature fly ash and finely ground slag were ingredients that were added to the proposed recipes. Consistency was determined by the method of cone seating and the density of fresh concrete. In the hardened state, concrete density, compressive strength, bending tensile strength, tensile strength, watertightness, concrete absorption, and abrasion resistance were determined using the Böhm method and wide wheel method. The test specimens were tested after 7, 28, and 90 days of maturation.

APA, Harvard, Vancouver, ISO, and other styles

10

Islam, G. "Evaluating reactivity and sorptivity of fly ash for use in concrete construction." Thesis, University of Dundee, 2012. https://discovery.dundee.ac.uk/en/studentTheses/94122abd-aa82-4c91-85ea-079505e14489.

Full text

Abstract:

This thesis describes research carried out to investigate techniques for (i) rapidly assessing the reactivity of fly ash; and (ii) evaluating its interaction with air-entraining admixtures (AEAs), both with regard to use in concrete. The materials considered for the project included, 54 fly ashes from 8 UK sources, and an additional three materials from Bangladesh, covering a range of fineness, loss-on-ignition (LOI) and production conditions (run-of-station, carbon removed, air-classified, co-combustion, oxy-fuel technology); Portland Cements (PCs) from five UK sources with various properties (strength classes 32.5 R, 42.5 N and 52.5 N); laboratory grade hydrated and quick limes; and three commercial AEAs and a standard laboratory grade reagent (surfactant). The research examining fly ash reactivity considered activity index tests to BS EN 450 (BSI, 2005c) as the reference and investigated tests covering fly ash properties/providing measures of fly ash behaviour to rapidly assess this. These included (i) fly ash fineness (45 µm sieve residue, or LASER particle size distribution (PSD) parameters), LOI and flow properties; (ii) accelerated curing of PC and lime-based mortars (iii) lime consumption by fly ash when combined with PC in paste or suspension (Frattini) or from a saturated lime solution; (iv) various measures of fly ash chemical composition (based on oxide/mineralogical analysis); and (v) a quicklime slaking test. The test results were validated by strength tests with 100 mm concrete cube. Results of the above indicated good correlations between fly ash fineness, mortar flow/water requirement and (pozzolanic) activity index (standard or accelerated curing). However, fly ash reactivity and fresh properties appeared to be influenced by the properties of the test PC (e.g. chemical composition and fineness) and there is a need to take this into account during assessment. Generally, finer fly ashes gave better flow; however, there is an optimum fineness (d90 ~40 µm) for best performance, and which is similar to the fineness of the test PC. Strong correlations between the accelerated and standard cured PC-based mortar indicate the latter can be used to estimate the former taking account of the fly ash properties. In view of eliminating the effect of PC properties on reactivity, mortar tests with laboratory grade hydrated lime suggested potential for this. However, for better assessment, this approach requires further work to address issues relating to slower rates of strength gain and increased time requirements, although high temperature conditions were used for curing. Measuring Ca(OH)2 consumption from fly ash/PC paste or suspension agreed with the behaviour in mortar, but needs special instruments (e.g. TGA or XRF). A similar approach with saturated lime did not work well, despite several measures being taken to try and improve this. The oxide and mineralogical analysis results of fly ash did not give good correlations with activity index, but improved when a factor combining them with fineness was considered. The test results were validated in concrete and with air-classified fly ashes from single sources which gave clear trend/behaviour. The lime slaking test was found to be ineffective for identifying fly ash reactivity. The reactivity assessment results were validated by carrying out concrete strength tests. In general, more consistent trends were obtained for fly ash from single source as noted with mortar earlier. Methods adopted/developed to assess the interaction of fly ash with AEA included (i) the foam index test; (ii) acid blue 80 (AB80) dye adsorption test (spectroscopic method); and (iii) methylene blue test. High variability in foam index test results between different operators were noted, which reflected differences in the degree of shaking applied and difficulties in identification of the test end point. Adoption of an automatic shaker and determination of suitable test conditions reduced this by more than 50%. Reliable test procedures were also established for the AB80 dye adsorption method. The results obtained from these tests gave very good correlations with fly ash specific surface area and the AEA dose required (both with commercial AEAs and standard reagent) for achieving target air contents in mortar and concrete. The methylene blue dye test also gave good correlations with these parameters, but was less effective for low LOI fly ashes. Between laboratory tests were carried out at three UKQAA members and considered, LOI, fineness (45 µm sieve and LASER PSD), and activity index. The results gave good agreement with those obtained at the Concrete Technology Unit for this work and again emphasized the role of fly ash fineness on its reactivity. Overall, fly ash fineness was found to be the best means of rapidly assessing its reactivity. Some of the other methods considered gave promising behaviour but require further refinements. Therefore, it is suggested that in addition to 45 µm sieve residue, other types of fineness measurement (e.g. sub 10 µm quantities, d50 and d90) can be considered suitable alternatives to activity index. Similarly, foam index tests with the automatic shaker or the AB80 test method could both be used as fly ash physical requirement tests, or in production control for air-entrained concrete.

APA, Harvard, Vancouver, ISO, and other styles

11

Vieira, Flávio de Lima. "Estudo da viabilidade do resíduo proveniente das porcelanas de isoladores para utilização em concretos bombeáveis estruturais." Universidade Federal de Goiás, 2017. http://repositorio.bc.ufg.br/tede/handle/tede/8131.

Full text

Abstract:

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-01-29T12:59:29Z No. of bitstreams: 2 Dissertação - Flávio de Lima Vieira - 2017.pdf: 3009793 bytes, checksum: f2afe605bb678159dc5e79283554d32b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)
Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-01-29T12:59:56Z (GMT) No. of bitstreams: 2 Dissertação - Flávio de Lima Vieira - 2017.pdf: 3009793 bytes, checksum: f2afe605bb678159dc5e79283554d32b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)
Made available in DSpace on 2018-01-29T12:59:56Z (GMT). No. of bitstreams: 2 Dissertação - Flávio de Lima Vieira - 2017.pdf: 3009793 bytes, checksum: f2afe605bb678159dc5e79283554d32b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-08-31
This research aims to evaluate the tecniques for disposal of waste obtained from electrical insulators. These pieces are one of the supplies widely used for electric power generation, and become a waste due to their replacement for new ones after maintenance and expansion works, in places like substations, generating units, distribution networks, transmission lines and its own production process. In Brazil, it is possible to acumulate waste from these insulators in courtyards and waste areas, besides wastelands, impairing the environment. Thus, it is known that an alternative for treatment is needed and the lack of knowledge and techical safe forces the development of reasearches about this subject, what are still in the beggining. So, this study proposes the evaluation of potential use of such a porcelain in concrete, through the replacement of conventional aggregates and cement. The research was conducted with a careful characterization of the waste in different maximum dimension sizes, with physicochemical and mineralogical analysis obtained from X-Ray diffration and images from scanning eletronic microscopy, for example. Besides, tests of alkali-aggregate reaction were perfomed in order to assess the chemical stability of the waste in mortar. Regarding to viscoelastic and mechanical properties, the compressive strength, modulus of elasticity, water absorption, and abrasion/erosion were performed. The experimental program considered eleven different mixes of pumped concrete, take into account the following replacement rates: 8% replacement of cement; 50% and 100% replacement of fine aggregate; and 45% and 100% replacement of coarse aggregate. Some mixes were done with both replacement of fine and coarse aggregate. The investigation of mechanical strength, deformation and durability, in conditions aforementioned, demonstrates that concrete with replacement was statistically similar to concrete without any replacement by waste, resulting a suitable concrete with porcelain waste content. The efficiency of compressive strength ranged from 0,087 MPa/kg to 0,107 MPa/kg and the modulus of elasticity reached values up to 38 GPa, indicating expressive results for these properties. Lastly, in research is possible to observe the conclusions about reological characteristics of all concrete and the influence of these replacement on cement content.
A presente pesquisa aborda a temática da destinação do resíduo dos isoladores elétricos proveniente da cadeia geradora de energia elétrica, como as relacionadas às manutenções e ampliações das subestações, unidades geradoras, redes de distribuição, linhas de transmissão e do próprio processo de produção do isolador. No Brasil esta cadeia acumula progressivamente resíduos em pátios e áreas de descarte, e às vezes esses materiais são lançados por terceiros em locais como terrenos baldios, impactando no meio ambiente. Nesse contexto, uma alternativa seria sua utilização para outros fins, os quais, por falta de conhecimento e segurança técnica, ainda se encontram em fases iniciais de estudo. Diante disso, a presente pesquisa propõe a investigação do potencial de uso destas porcelanas no concreto, em substituição aos agregados convencionais e também ao cimento. Para tanto, conduziu-se incialmente uma caracterização minuciosa do resíduo nas suas diversas dimensões, por meio de análises químicas, físicas e mineralógicas utilizando diferentes métodos, como a difração de raios X e imagens por microscópico eletrônico de varredura, por exemplo. Na sequência foram realizados testes para verificar a estabilidade química do resíduo em argamassa para o desencadeamento de reações álcalis-agregado. Em relação à sua incorporação no concreto, foram realizados ensaios para aferição da resistência à compressão, módulo de elasticidade, absorção de água, abrasão e erosão. As análises foram realizadas em onze concretos estruturais bombeáveis com diferentes teores de substituição, que contemplaram adição de 8% em substituição ao cimento, no agregado miúdo com 50% e 100% de substituição, no agregado graúdo com 45% e 100%, e em algumas composições com substituições simultâneas no miúdo e graúdo. De posse dos resultados, foi traçado um perfil de resistência mecânica, deformabilidade e durabilidade que apresentaram para algumas substituições valores estatisticamente iguais ao concreto sem resíduo, tornando factível a utilização do concreto com porcelana. Eficiências para resistência à compressão variando de 0,087 MPa/kg a 0,107 MPa/kg, módulo de elasticidade com valores de até 38 GPa, são números significativos para as propriedades. Análises da reologia do concreto e impactos no consumo de cimento são aspectos também observados e discutidos no decorrer do trabalho.

APA, Harvard, Vancouver, ISO, and other styles

12

Roubal, David. "Vývoj vysokopevnostních betonů s vysokým obsahem el. popílků." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392363.

Full text

Abstract:

This diploma thesis deals with the study of high-strength, high-volume fly ash concrete. The theoretical part of this thesis focuses on the detailed characteristic and main principles of high-strength concrete, high-volume fly ash concrete. In addition, according to the findings, the technology of high-strength and high-volume fly ash concrete, including principles of high strength, has been described. On the basis of the findings, high-strength, high-volume fly ash concrete for specific compressive strengths has been designed and created in the experimental section. These concretes were then subjected to a number of tests.

APA, Harvard, Vancouver, ISO, and other styles

13

Ivan, Lukić. "Komparativna analiza osnovnih svojstava konstrukcijskih betona spravljenih sa različitim vrstama lakih agregata." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=93149&source=NDLTD&language=en.

Full text

Abstract:

U disertaciji su prikazani rezultati sopstvenog eksperimentalnog istraživanja na osnovu kojih je izvršena komparativna analiza uticaja različitih vrsta lakih agregata i vrste i količine cementa na osnovna fizičko-mehanička svojstva lakoagregatnih betona. Takođe, analizirana je i mogućnost zamene dela cementa mineralnim dodacima u cilju smanjenja negativnih uticaja proizvodnje betona na životnu sredinu. Rezultati su pokazali da je primenom svih analiziranih vrsta agregata moguće dobiti konstrukcijski lakoagregatni beton, čak i sa manjim količinama cementa, odnosno sa zamenom dela cementa mineralnim dodacima, kao i da je moguće uspostaviti pouzdane korelacione veze između pojedinih svojstava betona i primenjenih komponentnih materijala.
In dissertation are presented results of own experimental research of acomparative analysis of the impact of different types of lightweightaggregates and the type and quantity of cement on basic physical andmechanical properties of structural lightweight concrete. Also, the possibilityof replacing part of cement with mineral admixtures is analyzed in order toreduce the negative impact of concrete production on the environment. Theresults showed that it is possible to obtain structural lightweight aggregateconcrete with all types of lightweight aggregates and even with lowerquantities of cement or with a replacement of part of a cement with mineraladmixtures. Also, it is possible to establish a reliable correlation betweencertain properties of concrete and used component materials.

APA, Harvard, Vancouver, ISO, and other styles

14

Lopes, Anne Neiry de Mendonça. "Mitigação da retração autógena em concretos de alta resistência contendo aditivo redutor de retração e seus efeitos na macro e microestrutura." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/38774.

Full text

Abstract:

O desenvolvimento do concreto de alta resistência - CAR foi um importante avanço na tecnologia de concreto, entretanto, a despeito de suas inúmeras vantagens como material estrutural, o seu emprego tem sido limitado, por ter se revelado mais susceptível à fissuração nas primeiras idades. Isto se deve à ocorrência do fenômeno da retração autógena, particularmente mais intenso nestes concretos que nos de resistência normal, uma vez que no CAR, há significativamente maior quantidade de material cimentício e menor quantidade de água, o que dá origem a uma estrutura porosa muito refinada logo nas primeiras idades, gerando altas magnitudes de tensões capilares. Além do estudo sobre o entendimento do fenômeno, as pesquisas atualmente têm buscado formas de mitigá-lo a fim de contribuir para estruturas mais duráveis. Diante do exposto, esta pesquisa investigou o comportamento do CAR, no tocante às propriedades mecânicas, elásticas e viscoelásticas e à durabilidade, quando empregado um aditivo redutor de retração - ARR que pode se configurar como estratégia mitigadora para a redução da retração autógena, bem como verificar a sua influência sobre a microestrutura e hidratação da pasta de cimento. Os resultados indicam que o ARR é eficaz na redução da retração autógena e retração por secagem, sem alterar de forma relevante as propriedades mecânicas e elásticas: a resistência à compressão sofre uma pequena queda de 5% com o uso de 2% de ARR em relação ao concreto referência, contudo, as demais propriedades não são alteradas com o uso do ARR. Quanto ao efeito sobre a fluência, não se obtiveram resultados conclusivos. A durabilidade, medida pelos ensaios de penetrabilidade a íons cloretos, permeabilidade à água, carbonatação natural e absorção capilar e por imersão, não é comprometida com a incorporação do aditivo redutor de retração. Do ponto de vista microestrutural, observou-se que o ARR altera o volume total de poros, embora de uma forma não muito expressiva; e ainda constatou-se que este aditivo afeta a velocidade de hidratação das pastas de cimento, e que possivelmente interage com compostos de hidratados da pasta, sem, no entanto, alterar as características macroestruturais do material.
The development of high strength concrete - HSC represented an important advance in concrete technology. However, even knowing that this kind of concrete has several advantages as a structural material, its application is limited by the early ages cracking. This occurrence is due to the autogenous shrinkage phenomenon, once HSC has a greater amount of cementitious material and a lower amount of water in relation to a normal-strength concrete. This condition implies in a greatly refinement of pore structure at early ages which lead to a higher magnitudes of capillary tension than the one observed in a normal-strength concrete. Beyond to study the phenomenon, much research has been conducted in many countries in order to reduce autogenous shrinkage and contribute to more durable structures. So, this research aims to investigate the effectiveness of shrinkage-reducing admixtures – SRA in decreasing the autogenous shrinkage of HSC, and mainly, verify its influence on viscoelastic, elastic and mechanicals properties and durability. The effect of SRA on microstructure and on the cement paste hydration was also investigated. The results show that SRA is effective in reducing the autogenous shrinkage and drying shrinkage without remarkable changes in elastic and mechanical properties. There were not conclusive results related to the creep property. The concrete durability under the action of aggressive agents (such as water, CO2 and chloride) was not influenced by the SRA, information provided by the results of chloride penetration, natural carbonation, water permeability, capillary absorption and absorption of water tests. In a microstructural point of view, it was observed that the addition of SRA results in a small rise in total pore volume. Besides, the results suggest that the SRA affects the rate of cement hydration and it can interact to the hydrated products of paste without implying in great influences on the macrostructural characteristics of the material.

APA, Harvard, Vancouver, ISO, and other styles

15

Pédèches, Jean-Michel. "Etude des proprietes mecaniques et du retrait de betons de haute performance." Toulouse 3, 1988. http://www.theses.fr/1988TOU30061.

Full text

Abstract:

Etude des betons avec resistance a la rupture en compression simple entre 30 et 130 mpa a 28 jours, realises par introduction de fumee de silice condensee et de fluidifiant. Dosage optimal de la fumee de silice (autour de 10% du poids du liant); variation des proprietes mecaniques, plus forte pour la resistance a la compression, avec fragilisation. Influence du fluidifiant sur la faible resistance a la compression aux jeunes ages et sur le retrait (moindre retrait avec la fumee de silice qu'avec les betons classiques d'egale resistance, fortement doses en ciment et/ou fluidifiant)

APA, Harvard, Vancouver, ISO, and other styles

16

Adel, Norelhayate. "Influence d'un adjuvant proteique sur la texture poreuse et les proprietes mecaniques et thermiques d'un beton cellulaire autoclave." Toulouse 3, 1987. http://www.theses.fr/1987TOU30219.

Full text

Abstract:

Etude en vue de la realisation de murs legers, isolants, homogenes, l'anisotropie de structure pouvant augmenter la resistance vertical et diminuer la conductivite horizontale. Etude de l'effect d'un siliceux, poudre d'aluminium et eau, autoclave a 175**(o)c. Les resultats s'expliquent par la structure dissymetrique vis-a-vis de l'eau des molecules proteiques, hydrophobes d'un cote et hydrofuges de l'autre

APA, Harvard, Vancouver, ISO, and other styles

17

Helnan-Moussa, Benjamin. "Influence de la température sur la thixotropie des bétons autoplaçants." Thesis, Artois, 2009. http://www.theses.fr/2009ARTO0203/document.

Full text

Abstract:

L’objectif de cette thèse est d’étudier l’influence de la température sur la thixotropie des bétons autoplaçants (BAP). L’intérêt de ce travail s’inscrit dans la perspective d’optimiser les formulations des BAP dans une large gamme de température. Un plan factoriel composite centré a été adopté dans le but de minimiser le nombre d’essais tout en étudiant les effets des facteurs (température et dosage en agent de viscosité (AV)) et leurs interactions sur les propriétés rhéologiques des BAP.La première phase de l’étude consistait à quantifier la thixotropie du béton juste après le malaxage et durant la période dormante en fonction du dosage en AV à des températures comprises entre 11.3 et 30.7°C selon le protocole proposé par Wallevik sur le rhéomètre BML4. Les résultats ont montré que l’indice de thixotropie présente un minimum respectivement pour un dosage en AV de 0.28 % (par rapport à la masse d’eau) et une température de 24°C. Cependant, ce protocole ne permet pas d’étudier la déstructuration des BAP, facteur recherché par exemple dans les coulages multicouches. Nous avons donc été amenés à retenir un protocole utilisé dans les gels et appelé protocole Dolz. L’application de ce dernier aux pâtes de ciment et aux BAP a permis de mettre en évidence une nouvelle grandeur, le potentiel de déstructuration K. Les valeurs du potentiel K montrent qu’au delà d’un certain dosage en AV et d’une certaine température, apparaissent des phénomènes d’encombrement qui réduisent le potentiel K. Ainsi, le potentiel K apporte des informations complémentaires pour l’aide à la sélection de dosages adéquats du couple superplastifiant – agent de viscosité en fonction de la température de coulage
The aim of this thesis was to study the influence of the temperature on the thixotropy of self-consolidating concrete (SCC). The research significance comes within the perspective to optimize the design of SCC in a wide range temperature. A factorial composite experimental plan was carried out in order to minimize the total number of tests while studying the effects of factors (temperature and dosage of viscosity modifying admixture (VMA)) and their interactions on the rheological properties of SCC. The first phase of the study was to quantify the thixotropy of concrete proportioned with various dosage of VMA at different temperatures ranging from 11.3 to 30.7°C just after mixing and at different time during the dormant period using the protocol proposed by Wallevik in BML4 rheometer. The results indicated that the values of thixotropy index present a minimum respectively with a VMA dosage of 0.28 % (by mass of water) and a temperature of 24°C.On the other hand, this protocol does not allow studying the destructuration of SCC, useful factor needed for example in the multi-layer casting. We therefore had to retain a protocol used in gels and called Dolz protocol. The application of this last to cement pastes and SCC has revealed a new grandeur, the potential of destructuration K. The values of K show that beyond a certain dosage in VMA and a certain temperature, the congestion phenomena appear that reduce the potential K. In this case, the potential of destructuration provides complementary information to assist in the selection of appropriate dosages of couple superlasticizer-VMA whatever the casting temperature may be

APA, Harvard, Vancouver, ISO, and other styles

18

Christianto, Heru Ari. "Effect Of Chemical And Mineral Admixtures On The Fresh Properties Of Self Compacting Mortars." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605322/index.pdf.

Full text

Abstract:

Fresh properties of mortars are important factors in altering the performance of self compacting concrete (SCC). Measurement of the rheological properties of the fine mortar part of concrete is generally used in the mix design of SCC. It can be stated that SCC rheology can be optimized if the fine mortar part of concrete is designed properly. However, measurement of the rheological properties is often impractical due to the need for complex equipment. Therefore, more practical methods of assessing mortar workability are often preferred. In this study, four mineral admixtures, three superplasticizers (SP) and two viscosity modifying admixtures (VMA) were used to prepare self compacting mortar (SCM). The mineral admixtures included fly-ash, brick powder, limestone powder, and kaolinite. Two of the SPs were polycarboxylate based and another one was melamine formaldehyde based. One of the viscosity modifying admixtures was based on an aqueous dispersion of microscopic silica and the other one was based on high molecular weight hydroxylated polymer. Within the scope of the experimental program, 43 mixes of SCM were prepared from different materials with keeping the amount of mixing water constant. Workability of the fresh mortar were determined using V - funnel and slump flow tests. The setting time of the mortars, were also determined. The hardened properties that were determined included the ultrasonic pulse velocity (UPV) and the strength which was determined at 7, 28, and 56 days. It was concluded that among the mineral admixtures used, only fly-ash and limestone powder increased the workability of the mixes. The two polycarboxylate based SPs yield approximately the same workability and the melamine formaldehyde based SP was not as effective as the other two.

APA, Harvard, Vancouver, ISO, and other styles

19

Gutierrez, Sanchez Juan Carlos, and Ramirez Juan Diego Ivan Salazar. "Evaluación de la permeabilidad en diseños de concreto con el uso de aditivos SIKA WT-100 y SIKA WT-200 en obras hidráulicas de Lima Metropolitana." Bachelor's thesis, Universidad Ricardo Palma, 2015. http://cybertesis.urp.edu.pe/handle/urp/1249.

Full text

Abstract:

Esta tesis tiene un enfoque cuantitativo, la cual propone evaluar la influencia de la permeabilidad en diseños de concreto con el uso de aditivos Sika WT – 100 y Sika WT – 200 en obras hidráulicas de Lima Metropolitana, debido a que estas estructuras almacenan y/o conducen grandes volúmenes de agua a una velocidad determinada, y éstas al tener contacto con el agua reducen su vida útil. Los objetivos de esta tesis son determinar la profundidad de penetración de agua bajo presión bajo la Norma Europea EN 12390 – 8 y la resistencia a la compresión bajo la Norma Técnica Peruana NTP 339.034; para finalmente, determinar la permeabilidad para diseños de concreto bajo la Norma Técnica Colombiana NTC 4483. Para lograr los objetivos mencionados, se diseñó y elaboró 144 probetas cilíndricas de concreto de 10 cm de diámetro y 20 cm de altura y 48 probetas cilíndricas de concreto de 15 cm de diámetro y de altura, de las cuales fueron 64 probetas de concreto patrón (sin uso de ningún aditivo), 64 probetas de concreto con aplicación de 2% de aditivo Sika WT – 100; y 64 probetas de concreto con aplicación de 1% de aditivo Sika WT – 200. Los resultados de los diseños de concreto patrón, WT – 100 y WT – 200 con una relación agua/cemento de 0.40, con respecto a la profundidad de penetración de agua bajo presión, fueron 40, 30 y 15 mm, respectivamente. Los resultados de los diseños de concreto patrón, WT – 100 y WT – 200, con respecto a la resistencia a la compresión a los 28 días con una relación agua/cemento de 0.40, fueron 637, 621 y 632 kg/cm2, respectivamente. Según la Norma Técnica Colombiana NTC 4483 y con los resultados obtenidos, se concluye que el diseño de concreto patrón y el diseño de concreto WT – 100 alcanzan una media permeabilidad y que el diseño de concreto WT – 200 alcanza una baja permeabilidad, con una relación agua/cemento de 0.40. This thesis has a quantitative focus, that propose to evaluate the influence of permeability concrete designs with the use of admixtures Sika WT – 100 and Sika WT – 200 in Metropolitan Lima waterworks, because these structures store and lead large volumes of water at a certain speed, and when these has contact with water reduces their useful life. The objectives of this thesis are to determine the depth of penetration of water under pressure under the European Norm EN 12390-8 and compressive strength under the Peruvian Technical Norm NTP 339.034; finally, determine the permeability of concrete designs under the Colombian Technical Norm NTC 4483. To achieve these objectives, we designed and developed 144 cylindrical concrete specimens 10 cm in diameter and 20 cm high and 48 cylindrical concrete specimens 15 cm in diameter and height, which were 64 concrete specimens pattern (without use of any admixture) concrete specimens 64 with application of 2% admixture Sika WT - 100; and 64 concrete specimens with application of 1% admixture Sika WT - 200. The results of pattern, WT – 100 and WT - 200 concrete designs with a water – cement ratio of 0.40, with respect to the depth of penetration of water under pressure, were 40, 30 and 15 mm, respectively. The results of pattern, WT – 100 and WT - 200 concrete designs with a water – cement ratio of 0.40, with respect to compressive strength at 28 days, were 637, 621 and 632 kg/cm2, respectively. According to the Colombian Technical Norm NTC 4483 and the obtained results, one can conclude that the pattern concrete design and WT - 100 concrete design reach a medium permeability and concrete design WT - 200 reaches a high permeability, with a water – cement ratio of 0.40.

APA, Harvard, Vancouver, ISO, and other styles

20

LIMA, Marcelo Batista. "Avaliação da capacidade de proteção contra a corrosão da arma-dura induzida por cloretos de concretos com adições minerais e inibidores de corrosão." Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/1347.

Full text

Abstract:

Made available in DSpace on 2014-07-29T15:18:24Z (GMT). No. of bitstreams: 1 pretextual.pdf: 140883 bytes, checksum: 5d9ee4b9b3884a0032825e604304580f (MD5) Previous issue date: 2009-09-28
Increasing the durability of concrete structural elements is primordial, especially those related to power generation in eolic areas that are subjected to the phenomenon of reinforcement corrosion. In this context, this study aims to evaluate the overall protection ability of concrete to the phenomenon of reinforcement corrosion induced by chlorides. To this end, it was adopted a statistical program based on a fractional factorial design in which the variables studied were as follows: the water-binder ratio (0.35, 0.45 and 0.55), the type of mineral admixture (silica fume and blast furnace slag at specific levels), the type of corrosion inhibitor (calcium nitrite, sodium nitrite and amine) and the level of corrosion inhibitor (minimum and maximum recommended by each manufacturer). In the concrete investigations, the tests performed were corrosion potential, polarization resistance and electrochemical impedance. Throughout the experiments, it was possible to testify the beneficial effect of reducing the water-binder ratio. It was also possible to prove the very positive effect of the incorporation of mineral admixtures, especially of silica fume. The satisfactory performance of various inhibitors evaluated was also verified, specially when concrete contains mineral admixtures. A parallel study was conducted to make a comparative analysis of inhibitors at the same range of concentrations (at solid levels of 0.76%, 2.21% and 3.66% of the compound on the cement mass), nevertheless this study have demonstrated that fixing contents for all inhibitor is not appropriated, and the recommended dosages by the manufacturer is the best condition. As the levels recommended by manufacturers, it was found that the higher percentages have not worked well for sodium nitrite otherwise, for amine and nitrite calcium, the higher levels implied better results. Regarding the tannin inhibitor also assessed in the parallel study mentioned above (related to specific inhibitors), its good performance related to corrosion inhibition happened just for the content of 0.76% (the lowest levels). For the other contents, it was verified anomalous results. These results demonstrated that each type of corrosion inhibitor has its optimal concentration for use in concrete. Based on a cost-benefit analysis and evaluating the increase in the concrete value for cubic meter (in R$) in the presence of inhibitors at the same contents, it was verified a relative parity prices among the tested nitrites and an extremely high cost of amine. However, when performing the same analysis but using the levels recommended by the manufacturers for each inhibitor independent, it was found that the large disparity in prices between nitrite and amine was reduced considerably. An assessment of technical and economic feasibility was also performed based on the efficiency of corrosion inhibition and cost per cubic meter of concrete mixtures that did not show a typical depassivation of their stell bar up to the attack age evaluated
O aumento da durabilidade é um aspecto primordial para os elementos estruturais de concreto, em especial aqueles constituintes das estruturas de geração de energia em parques eólicos, sujeitos ao fenômeno de corrosão das armaduras. Nesse contexto, este trabalho tem como objetivo geral avaliar a capacidade de proteção de diferentes concretoS frente ao fenômeno da corrosão da armadura induzida por cloretos. Para tanto, foi adotado um planejamento estatístico baseado em um modelo fatorial fracionado em que as variáveis estudadas foram: a relação água/aglomerante (0,35; 0,45 e 0,55), o tipo de adição mineral (sílica ativa e escória de alto-forno, em teores específicos), o tipo de inibidor de corrosão (nitrito de cálcio, nitrito de sódio e amina) e o teor de inibidor de corrosão (mínimo e máximo recomendado por cada fabricante). Na avaliação dos concretos, foram realizados ensaios de potencial de corrosão, resistência de polarização e impedância eletroquímica. Ao longo de todo experimento foi possível constatar o efeito benéfico da redução da relação a/agl. Também foi possível verificar o efeito extremamente positivo da incorporação das adições minerais, em especial da sílica ativa. Constatou-se também o efeito positivo dos diversos inibidores avaliados, em seus teores mínimo e máximo, beneficio que se mostrou mais pronunciado quando da utilização conjunta com as adições minerais. Um estudo paralelo foi realizado para se fazer uma análise comparativa dos inibidores dentro da mesma faixa de teores empregados (teores de 0,76%; 2,21% e 3,66% de sólidos do aditivo em relação à massa de cimento), no qual se verificou que a utilização desses teores fixos para os diferentes tipos de inibidores não se mostrou tão eficiente quanto em relação à utilização dos aditivos na dosagem de recomendação do fabricante. Quanto a estes teores (recomendados pelos fabricantes), verificou-se que os percentuais mais altos não funcionaram bem para o nitrito de sódio, ao passo que para a amina e para o nitrito de cálcio os teores mais elevados resultaram em melhores resultados. Em relação ao tanino, inibidor que também foi avaliado no estudo paralelo referido anteriormente (específico sobre os inibidores), só houve algum resultado de inibição de corrosão para o teor de 0,76% (mais baixo dos teores), tendo-se obtido resultados anômalos para os outros 2 teores mais altos. Tais resultados permitiram constatar que cada tipo de inibidor de corrosão possui sua concentração ótima de utilização no concreto. Fazendo-se uma análise de custo e avaliando-se o acréscimo em Reais no valor do m3 do concreto proporcionado pelos diversos aditivos inibidores e nos teores de mesma faixa de emprego, verificou-se uma relativa paridade de preços entre os nitritos e um elevadíssimo custo da amina. No entanto, ao se realizar a mesma análise, mas utilizando os teores recomendados pelos fabricantes de cada inibidor, verificou-se que a grande disparidade de preços entre os nitritos e a amina foi reduzida de forma considerável. Uma avaliação da viabilidade técnico-econômica dos concretos também foi realizada, a partir dos dados de eficiência de inibição à corrosão e custo/m3 das misturas que não apresentaram comportamento típico de despassivação de suas armaduras até a idade de ataque considerada

APA, Harvard, Vancouver, ISO, and other styles

21

Fleischhacker, Ján. "Vliv technologie výroby popílkového pórobetonu na vznik tobermoritických fází." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240077.

Full text

Abstract:

Autoclaved aerated concrete is long-time ecological building material with usefull properties. There needs to be done research of its mineralogical compound for reengineering the production. The main mineral compound of AAC is tobermorite, it increases its mechanical properties. In the presence study, we examine the usage of nature and artificial silicious materials. Also, we investigate the influence of sulfate and alumina admixtures, as well as fluidized bed combustion ash, which can be used as the lime and gypsum replacement. Closure of the study is design of the optimal raw material composition, also hydrothermal treatment of autoclaved aerated concrete. In relation to its mechanical properties, mineralogical composition and cost.

APA, Harvard, Vancouver, ISO, and other styles

22

Tran, Duc Long. "Impact of intrinsic granular porosity on the durability properties of concrete." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30021.

Full text

Abstract:

La préservation des ressources naturelles et la limitation des émissions de CO2 sont une contribution au développement durable. Dans le cadre de la conception du béton, cette contribution consiste à utiliser des granulats locaux ou recyclés. Cependant, ces derniers peuvent être poreux et de faible qualité. La communauté scientifique est d'accord sur le fait que la porosité intrinsèque des granulats modifie les propriétés de transport du béton, mais dans quelle mesure reste une question. L'objectif de la thèse est d'analyser l'impact de la porosité intrinsèque des granulats grossiers, principalement sur les propriétés de durabilité du béton. Dans une compréhension préliminaire et en vue d'accentuer les phénomènes se produisant dans le béton, un programme expérimental est conçu pour le modèle élémentaire (EM), qui est composé de pâte et de gravier. L'impact de la nature des granulats (poreux et non poreux), de l'état d'humidité et du volume ainsi que de la nature du liant, est analysé sur i) la porosité de l'eau du modèle élémentaire, ii) la structuration de l'interface pâte-granulat. Ensuite, à l'échelle du béton, les matériaux ont été conçus avec le même squelette de granulats (même sable) et la même teneur équivalente en liant. Les conceptions variaient selon la nature des granulats, l'état d'humidité, la nature du liant, la variation du rapport eau/ciment et l'incorporation d'adjuvants chimiques (plastifiant ou superplastifiant). L'impact de la porosité des granulats grossiers sur les propriétés à l'état frais (affaissement, densité apparente et teneur en air emprisonné) et à l'état durci (résistance à la compression, porosité de l'eau, absorption d'eau, perméabilité aux gaz, migration des chlorures, carbonatation accélérée et teneur en portlandite) a été étudié. Les principaux résultats montrent que l'état d'humidité des agrégats et la nature du liant sont les premiers facteurs qui conditionnent la structuration de l'interface pâte/agrégats au sein du modèle élémentaire. La nécessité d'utiliser des agrégats poreux en surface saturée et sèche est particulièrement mise en évidence. À l'échelle du béton, les propriétés à l'état frais sont influencées par la porosité des granulats et le rapport eau/liant (W/B). Cependant, pour un rapport eau/liant fixe correspondant à une consistance fluide, les variations des propriétés à l'état frais mesurées lors de l'incorporation de granulats poreux ne dépendent pas de la nature du liant. Dans le béton durci, la porosité des granulats joue un rôle important dans la porosité de l'eau et la perméabilité à l'air du béton, quelle que soit la nature du liant. Pour les autres propriétés de durabilité (absorption d'eau, migration de Clo, carbonatation et résistance à la compression), la nature du liant l'emporte sur la porosité des granulats
The preservation of natural resources and the limitation of CO2 emissions are a contribution to sustainable development. In the context of the concrete design, this contribution consists in using local or recycled aggregates. However, local or recycled aggregates can be porous and of low quality.The scientific community agrees that the intrinsic porosity of aggregates changes the transport properties of concrete, but to what extent is still a question. The objective of the thesis is to analyze the impact of intrinsic coarse aggregate porosity on mainly the durability properties of concrete. In a preliminary understanding and with a view to accentuating phenomena occurring in the concrete, an experimental program is designed for elementary model (EM), which is composed of paste and gravel. The impact of the aggregate nature (porous and non-porous), moisture state and volume together with the binder nature, is analyzed on i) the water porosity of EM, ii) the structuration of the paste-aggregate interface. Next, at concrete scale, materials were designed with the same skeleton of aggregates (same sand) and the same equivalent binder content. The designs varied by the aggregate nature, moisture state, the binder nature, the variation of water/cement ratio and the incorporation of chemical admixtures (plasticizer or superplasticizer). The impact of coarse aggregate porosity on properties in the fresh state (slump, apparent density and entrapped air content) and in the hardened state (compressive strength, water porosity, water absorption, gas permeability, chloride migration, accelerated carbonation and Portlandite content) was studied. The main results show that the moisture state of aggregate and the binder nature are the first factors that condition the structuring of the paste/aggregate interface within the elementary model. The necessity to use porous aggregates in saturated surface dry is particularly highlighted. At the scale of concrete, the properties in the fresh state are influenced by the aggregate porosity and the water/binder (W/B) ratio. However, for a fixed W/B ratio corresponding to fluid consistency, the variations in the fresh properties measured when porous aggregates are incorporated do not depend on the binder nature. In hardened concrete, porosity of aggregate plays an important role in water porosity and air permeability of concrete whatever the nature of binder. For other durability properties (water absorption, Clo migration, carbonation and compressive strength), the nature of binder overcome leading in comparison to the porosity of aggregate

APA, Harvard, Vancouver, ISO, and other styles

23

Lo, Yung-hsiang, and 羅永祥. "The performance of Lightweight Aggregate Concrete using Admixture." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/93808435128963024463.

Full text

Abstract:

碩士
國立中興大學
土木工程學系所
101
Self-consolidating concrete with high flow-ability and segregation resistance was a great contribution to construction technology. This study mainly presents that the effects of admixtures on fresh and hardened properties of lightweight aggregate concrete. In order to obtain more appropriate mixture proportions of high flow lightweight aggregate concrete for application in construction site, the various type of admixtures composed of different molecular chains, fly ash contents, and total binder amounts were adopted to evaluate the suitability of self-consolidating lightweight aggregate concrete (SCLC). The test results indicate that the fresh properties (e.g. slump flow, U-box, V-funnel test results) of self-consolidating lightweight aggregate concrete using the admixture with high molecular weight and long molecular chains were in accordance with normal weight concrete through controlling the visible viscosity of various admixtures. Both hardened properties and homogeneity of elf-consolidating lightweight aggregate concrete satisfied the basic requirements. In terms of replacement (10 to 40 % by weight) of cement with fly ash in this study, at least a 30 % replacement of cement with fly ash by weight and a 1.77 volume ratio of mortar and lightweight aggregate were proposed for designing high flow lightweight aggregate concrete with better fresh properties. The flow velocity of high flow lightweight aggregate concrete was slightly slower than normal weight concrete due to the high flow lightweight aggregate concrete with lighter unit weight and more viscosity. Even so, slump flow test results show that the flow-ability of high flow lightweight aggregate concrete should satisfy demands for application in construction site. But the slump flow was over 700 mm, the high flow lightweight aggregate concrete would probably occur the potential crises of segregation and lightweight aggregate floating. Keywords: Lightweight aggregate, Admixture, Self-consolidating lightweight aggregate concrete (SCLC)

APA, Harvard, Vancouver, ISO, and other styles

24

Feng, Chi-Hsiang, and 奉季祥. "Study of Viscosity-Enhancing-Admixture for Self-Compacting Concrete." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/66423715083730499826.

Full text

Abstract:

碩士
國立交通大學
土木工程系所
92
At current time, it is still difficult to produce SCC of constant quality at ordinary ready-mixed concrete plants because facilities and quality control of materials had not reached the required level. To improve manufacturing and handling, a viscosity agent (VA) was added to the mixtures. This paper will use different kind of viscosity enhancing admixtures (VEA) to produce different kinds of SCC and study the influence of VEA on self-compacting concrete. Different volume of coarse aggregates were employed to understand the materials influence on SCC .The results obtained indicate that using of viscosity enhancing admixtures (VEA) has proved to be very effective in stabilizing the rheological properties and consistency of self-compacting concrete .It is possible to reduce quality fluctuations in a fresh state for commonly available materials and production facilities. Creep & shrinkage was studied to understand the mechanical properties of these SCC.

APA, Harvard, Vancouver, ISO, and other styles

25

Yen, Pao-Yi, and 顏保儀. "Study on PCB Admixture Applying on Constructed Concrete Engineering." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/jt36t5.

Full text

Abstract:

碩士
國立臺北科技大學
土木與防災研究所
99
The purpose of the study is to search the possibility of PCB wasted powder replace part of fine aggregate in normal concrete, it might reuse waste, getting better workability, higher slump then improving construction quality. We use the present concrete of Lungmen project of TPC to match quality required on the study. At first, setting non-waste-contained as the negative controls and then let PCB replace fine aggregate by 2.5%, 5%, 7.5%, 10% and 15% to see the performance of initial and hardened period of concrete. The results of study shows that slump is getting higher when increasing replaced quantity, the minimum and maximum value between 190-240mm, about 50mm variation. Besides, the normal concrete only has 199.5C.C. bleeding after 220 minutes, however it up 230C.C. to 441C.C. when add 2.5% to 15% PCB in it. For the initial setting time, it''s similar to normal concrete when admixture is under 10%, but increasing 8% (about 1 hour) if over 10%. The initial setting time is about 13 hours at 2.5% admixture, 16 hours for 5% and 10%, but it can''t reach final setting even 18 hours pasted for 15%. The compressive strength has obviously variety, it shows non-PCB-contained is better than PCB-contained before ages of 28 days, and continue developing after 42 days. The strength of 2.5%-PCB-contained is 12% higher than non-PCB-contained after 90 days. Therefore, the best substitution rate of PCB is between 5% and 10%. There is no evidence shows admixture rate effects drying shrinkage in this study, and the of shrinkage-graph of each group is pretty closed. The drying shrinkage value is decreasing while curing ages increased. For the toxicity liberation, its quantity within PCB, in TCLP testing result, is extremely low after concrete hardened. There is only 1% of Cu safety value released at 15% rate, which means hardened toxicity is well.

APA, Harvard, Vancouver, ISO, and other styles

26

Chiu, Yi-Cheng, and 邱翊承. "Influence of Green Admixture on Pore Structures of Concrete." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/448s85.

Full text

Abstract:

碩士
國立東華大學
材料科學與工程學系
107
Concrete is a porous composite，various sizes of internal pores exist even after cement hydration. External harmful masses would dissolve in pore water and pass in concrete, which may result in concrete degradation and life reduction. In order to improve concrete durability, use of pozzolanic materials or ggbs as supplementary cementing material may reduce the amount or size of pore structure. Fly ash, silica fume and ggbs as partial cementing materials were used in the testing program and replacement percentages for cement were 10%, 20% and 30%. The water-cementitious ratios of mixtures were 0.4 and 0.6. Mortar specimens were cast in the lab. Physical properties and durability tests were conducted to evaluate the pore structures of cement-based composites. Test results illustrate mortar specimen with 30% ggbs replacement has most dense pore structure.

APA, Harvard, Vancouver, ISO, and other styles

27

洪文堂. "Effects of Anti-Permeation Admixture on the Durability of Concrete." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/04265417700880119567.

Full text

Abstract:

碩士
國立中興大學
土木工程學系
91
ABSTRACT A series experiment were carried out to investigate the mechanical properties of concrete adding anti-permeation admixture. The test items included slump test, setting time of fresh concrete and the compressive strength, splitting strength, flexible strength, volume change, electrical resistance, permeability and abrasion resistant properties of harden concrete. . The water-cement ratios and anti-permeation admixture proportions were variable in the study .Three water-cement ratios (W/C=0.57, 0.35, and 0.28)and four anti-permeation admixture proportions(0%, 8%, 10%, 12%) were used in test .The normal concrete (adding 0% anti-permeation admixture ) was a control batch. The results show that the volume change and permeability of concrete will be decreased as adding concrete anti-permeation admixture. The mechanical properties and abrasion resistant properties of concrete adding anti-permeation admixture were higher than that of control batch. The results indicate that adding anti-permeation admixture in concrete will make the concrete denser and more durable.

APA, Harvard, Vancouver, ISO, and other styles

28

Shen, Chen-Nan, and 沈政南. "Study on the Fire Resistance of Concrete with Chemical Admixture." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/20730070192355525696.

Full text

Abstract:

碩士
國立臺灣科技大學
營建工程技術學系
82
This study mainly investigates the influence of chemical admixture on the fire resistance of concrete . The type of admixture used are common in engineering field including type A,C,D,F and G. The specimens were made for macro/micro and mechanical property test. An electric furnace was used to simulate a high temperature environment. All the test results were compared with those of pure concrete(no chemical admixture) to assess the influence of chemical admixture on the fire resistance of concrete. This research also investigates the mechanism of fire resistance from the inserting of chemical admixture into the cement paste, mortar and concrete. The results show that chemical admixture except type A and type C has positive effect for the fire resistance on concrete, especially by adding superplasticizer(ie.type F) . According to XRD and SEM , superplasticizer can refine cement paste and reduce voids. Ultrasonic tests also prove that chemical admixture can improve the interfaces of aggregate in concrete. The residual strength reduction of concrete with chemiical admixture has been found slighter. The out-look is almost the same as that concrete with no chemical admixture.

APA, Harvard, Vancouver, ISO, and other styles

29

Shieh, Horng-Jeu, and 謝竑舉. "Study on Basic Oxygen Furnace Slag Applying for Concrete Admixture." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/34502628890110299143.

Full text

Abstract:

碩士
國立屏東科技大學
環境工程與科學系
93
The Contents of Abstract in this Thesis： There are two ways of exploitation about slag. They include that BOF slag powder substitute for part of fly ash-slag powder and regards BOF slag powder as low reactivity mineral admixtures. This study goes on with four steps. The first one is to select the best handling process and method. The second one is to handle different batches of BOF slag according to previous selection method. Namely, taking the samples to pass through the No. 4 standard sieves and grind them through No.100 standard sieves. Then they are mixed in different percentage with type I Portland cement, granulated blast furnace slag, F class fly ash, and standard sand to form paste and mortar samples. In addition, it is referred by the CNS Chinese National Standard No. 1258 “method of test for autoclave expansion of Portland cement” and tests the soundness of samples which is added in different rate of BOF slag powder and repeats it three times repeatedly. The third stage is to add BOF slag powder of different fineness which is the fixed percentage. The last stage is to select BOF slag of different characters and discuss the relationship between temperature, texture and of BOF slag expansion ratio (10 days). Finally, we also utilize statistics software to analyze the contribution degree of free CaO to BOF slag expansion ratio (10 days). The experimental results are listed as follows: 1.In using BOF slag powder in substitution for parts of fly ash-slag powder, the weight ratio of type I Portland cement and fly ash-slag powder and BOF slag powder is 50-35-15. The result can fill the bill. 2.In regarding BOF slag powder as low reactivity mineral admixtures, the volume rate of Type IS(MS) Portland-Slag Cement and standard sand is 1-2.75. BOF slag powder replaces the volume of standard sand 15% that it can fill the bill. 3.In fixed rate of the weight rate of type I Portland cement and fly ash -slag powder and BOF slag powder is 50-30-20. In coarse aggregate, only after stabilizing for 15 days and grinding the samples to pass through NO. 100 standard sieves, it can agree with the safe demand of adding amount. In fine aggregate, after stabilizing for 5 days and grinding the samples to pass through NO. 100 BOF slag powder, it also can agree with the safe demand of adding amount. 4.The expansion ratio (10 days) of different character BOF slag (Air-cooled) is that the BOF slag NO.2 (porosity) is bigger than BOF slag NO.1 (gray and brown) and greater than BOF slag NO.4 (part of porous and dense) and greater than BOF slag NO.3 (dense). The higher the water temperature is, the faster the expansibility is. 5.As for analysis data, the contribution degree of free CaO factor of BOF slag whose diameter is smaller than 4.75 mm to expansion ratio (10 days) is 66.63%.

APA, Harvard, Vancouver, ISO, and other styles

30

Lin, Jiun-Hong, and 林俊宏. "A Study of Rubber Admixture in Concrete on Damping Ratio Property." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/64865999098933953213.

Full text

Abstract:

碩士
國立成功大學
建築學系碩博士班
95
Previous research revealed that the vibration of machines and pipelines in the factory transferred to foundation via floor caused reduction in production rate and quality of the product. Thus, the vibration problem of the floor needs to be solved so as to ensure the normal operation of the precision equipment and instrument in the factory. The aim of this study is to explore the influence of rubber admixture, including #10 and #40, and air entraining agent, in concrete on damping ratio property. However, adding the rubber admixture will somehow reduce the compression strength (fc’). Therefore, the first part of this study is to discuss the parameter of mixing-ratio to determine the mechanical properties, such as the compression strength (fc’) and the Young’s Modulus, of the concrete cylinder with different admixture. The second part of this study is to perform the impulse test to determine the damping ratio of the cantilever beam specimen made of concrete to identify the influences of different admixture, mixing-ratio, tamping method, and age effect. The impulse test is to impact the specimen by impulse-force hammer and measure the response of the specimen by an accelerometer mounted on the cantilever end of the specimen. Acceleration values during free vibration decay response were measured and analyzed by logarithmic decrement calculation to estimate the damping ratio. The experimental results show that: 1.The compression strength and the Young’s Modulus of the concretes are lower with the rising of the mixing-ratio of the rubber powder. For the rubber admixture added not exceeding 7.5%, the strength reduced at most 27% with adding #10 rubber powder, 41% with adding #40 rubber powder, respectively. 2.The peaks of the vibration influence the damping ratio of the reaction of the cantilever beam specimen. The larger excitation brings about the higher damping ratio. With reducing amplitudes, the damping ratio of the specimen is lower. 3.The admixture of rubber powder is useful in raising the damping ratio of the concrete. For the rubber admixture added not exceeding 7.5%, the damping ratio increased at most 110% with adding #10 rubber powder, 140% with adding #40 rubber powder, respectively. 4.Tamp down by tamping rod while constructing the specimen can increase the concrete’s damping ratio by 160%, but reduce 15% of the compression strength (fc’) of the concrete specimen. 5.The admixture of air entraining agent are useful in raising the damping ratio of the concrete, for the air contained in the concrete increase 6%, the damping ratio increase 40%. 6.With the aging of the concrete, the damping ratio decreases due to the influence of hydration and evaporation of water molecules in the concrete. 7.Results of this study showed that the improvement in damping may be due to the interfacial debonding and the subsequent interfacial friction.

APA, Harvard, Vancouver, ISO, and other styles

31

Chen, Shan-Shou, and 陳善壽. "A Mathematical Model for Predicting Carbonation of Concrete with Pozzolanic admixture." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/19853053304463842291.

Full text

Abstract:

碩士
國立成功大學
土木工程學系碩博士班
91
The carbonation process and the factors affecting concrete carbonation are presented in this study. A mathematical model based on carbonation process for predicting the carbonation depth of concrete with Pozzolanic admixture was developed. An accelerated carbonation test was conducted on ordinary Portland cement (OPC) and slag concrete (SC). The depths of carbonation predicted from the model are compared with the test results. It is shown that the effective water/binder ratio and the cement content are the key factors affecting the carbonation of slag concrete. It is shown that the carbonation of concrete may improve the compressive strength, splitting tensile strength, and elastic modulus. It also appears that the carbonation depth increases as the water/cement ratio increases at the same concentration of CO2 and duration of exposure. Besides, the carbonation rate by the specimens of OPC is faster than by the specimens of SC. Finally, the agreement between test results and the prediction from the model is good. This model can be used to predict the evolution of carbonation depth with time. This model also can offer researchers significant references about concrete carbonation theory.

APA, Harvard, Vancouver, ISO, and other styles

32

Cheng, Ming-Yao, and 鄭名堯. "The Effect of the Mineral Admixture on Permeability Properties of Concrete." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/88695045609554839961.

Full text

Abstract:

碩士
東南技術學院
防災科技研究所
94
The purpose of this study is to evaluate the effect of mineral admixtures on mechanical properties and permeability of concrete. Mineral admixtures were used in the various mixes to replace the concrete usage and control the environment factors (high temperature, loading) and water binder ratio. The test results show that concrete with adding anti – permeation in high temperature will advance the permeability; the permeability of concrete will be advanced along with the load increment. The permeability advancement is happened also in anti – permeation paste. Besides the anti – permeation concrete also plays a big role in impermeability effect, the optimum adjunction is 6%. In addition, both of the electrical resistance value and Ultrasonic Pulse Velocity become higher.

APA, Harvard, Vancouver, ISO, and other styles

33

Nai-Min, Huang, and 黃乃明. "Effect of Mineral Admixture on the Properities of High Performance Concrete." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/04530110170556743000.

Full text

Abstract:

碩士
國立臺北科技大學
土木與防災技術研究所
92
This paper is to study the effect of the workability of high performance concrete with aggregate and mineral admixture. Test variables include the sand over aggregate and the mineral admixture replacement. The slump test, slump flow test, and passing height from U test were performed to correlate the effect of the workability, and test for compressive strength and elastic modulus. The testing results indicate that the compressive strength and elastic modulus are not significantly affected by sand ratio computed from a constant aggregate volume, but are influenced by the elastic properties of the paste. The workability test results indicate that can increase of sand ratio can improve workabi1ity of HPC. Slag is better than fly ash in HPC mixture as far as workability is concerned.

APA, Harvard, Vancouver, ISO, and other styles

34

HO, CHUNG-TA, and 何宗達. "The Effect of Copolymer Chemical Admixture on the Engineering Properties of Concrete." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/18308737481368916352.

Full text

Abstract:

碩士
國立高雄應用科技大學
土木工程與防災科技研究所
96
This study is focused on the investigation of how a new copolymer chemical admixture affects the engineering properties of concrete.This research adopts two mixture designs (ACI mixture design algorithm and Densities mixture design algorithm). We fix the PD dosage and change the water-to-binder ratio (W/B = 0.30, 0.36, 0.42) to mix concrete, and use the cement paste and mortar to figure out how the Copolymer Chemical Admixture affects the cement beforehand.The tested items include fresh concrete (slump, slump flow, slump loss, setting time, air contain and unit weight) and hardened concrete (compressive strength, ultrasonic pulse velocity, electrical resistance, length change and SEM microstructure observation).Its result shows that because the PD has positive and negative ion and can adsorb on the cement particle to disperse, so we can reduce the water-to-cement ratio and extend the setting time by water reduction. The compressive strength, ultrasonic pulse velocity and rebound hammer number also increase 25%. In ACI mixture design algorithm, the water-reducing ratio exceeds the 12% which specified in CNS standard. It means the PD belongs to Water-reducing high range admixtures and has 1.5 ~ 3 hours set-retarding compared to control concrete.In Densities mixture design algorithm, the comparison of three kinds of PD and SPF, the slump loss of PD is smaller, setting time is longer, ultrasonic pulse velocity and resistance value slightly less than SPF. The entire performance of PD is between Type F and Type G in CNS 12283.

APA, Harvard, Vancouver, ISO, and other styles

35

蔡宜珍. "Study on permeability of concrete with mineral admixture using gas permeability method." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/70130133011936322983.

Full text

Abstract:

碩士
國立臺灣科技大學
營建工程系
91
By using the properties of low burning temperature and easy vaporization for methanol liquid, this research conducted various gas permeability experiments on concrete specimens. First of all, the mechanism of gas permeability method was established. Then, different variables such as the thickness of specimen, water to binder ratio (W/B), addition of Pozzolanic materials and compressive strength of cylinderical specimen, etc. were used in the gas permeability experiments to study the feasibility for assessing the durability of concrete. Experimental results show that the thickness of the specimens used in the methanol permeability test has better be bigger than the maximum size of aggregate; the permeability of concrete with high W/B is greater than that with low W/B. Taking the concrete with slag as an example, the concrete specimen with W/B of 0.65 and thickness of 20 mm at age of 365 days has a coefficient of permeability of 3.596E-17m2, that is higher than 2.911E-17 m2 for a concrete specimen with W/B of 0.5. Adding Pozzolanic material into concrete reduces its permeability. The permeability coefficient of pure concrete is the biggest, concrete with slag is smaller, and concrete with fly ash is the smallest. Taking concrete specimen with W/B of 0.55 and thickness of 10 mm as an example, at age of 365 days, the coefficient of permeability is 2.038E-17 m2 for F55 concrete specimen (adding fly ash), 2.208E-17 m2 for S55 concrete specimen (adding slag) and 7.730E-17 m2 for C55 pure concrete specimen. The sequential relationship of the coefficient of permeability for these three kinds of concrete matches those results in previously published papers. The coefficients of permeability of concrete will decrease with the increase of its compressive strengths or the addition of pozzolanic materials. The order of the reducing rate of coefficient of permeability for concrete specimens is F65 concrete with fly ash (smallest), S65 concrete with slag, and C65 pure concrete (biggest).

APA, Harvard, Vancouver, ISO, and other styles

36

Lin, Siao-Shan, and 林筱珊. "Effect of Admixture and Water-to-Binder Ratio on Hydration Heat of Mass Concrete." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/bs6vea.

Full text

Abstract:

碩士
國立嘉義大學
土木與水資源工程學系研究所
106
In this study, three groups of water-to-binder ratio (0.3, 0.4, 0.45), five groups of slag and fly ash substitution rate (0%, 40%, 50%, 60%, 65%) and two chemical agents, strong plasticizers and retarders, a total of nine groups of ratios, to explore the effect of the admixture and water-to-binder ratio on the hydration heat in the initial stage of concrete condensation. In addition, two sets of ratios were used to carry out large-scale trials on the spot to simulate the actual construction of the mass concrete. The laboratory results showed that the initial setting time of each group of fresh concrete was between 5.5 and 8.8 hours, and the final setting time was between 7.9 and 11.2 hours. The initial setting time of retarded concrete was extended to 22 hours and the final setting time was extended to 71 hours. The compressive strength of each group of concrete is more than 27.5MPa in 28 days. In terms of concrete hydration heat, when the water-to-binder ratio is 0.45, the substitution of slag and fly ash is increased, and the maximum heart temperature and hydration heat temperature rise rate and temperature drop rate are lower; the heart surface temperature difference is between 0.76 and 1.18 °C, of which pure The cement concrete core surface has the largest temperature difference, followed by the slag replacement amount of 65%, and the slag and fly ash substitution amount of 40%, 60%, 65% and 50%. When the substitution amount of slag and fly ash is 65% (35% of slag and 30% of fly ash), the maximum temperature of retarded concrete is only 79% of pure concrete. The hydration heat temperature rise rate of the retarded concrete did not change significantly within 72 hours, and began to rise slowly after 72 hours, reaching the maximum temperature at 110 hours. On the other hand, the local test (2m × 2m × 2m) uses slag and fly ash concrete and retarded concrete. Block A is completely placed on the slag and fly ash concrete, and the bottom of the block B is first poured with a retarding concrete thickness of about 40 cm, and then the slag and fly ash concrete is poured. From the measurement results of hydration heat, the maximum heart temperature of block A occurred at 58.6 °C at 43 hours, and the maximum heart temperature difference was 18.3 °C; the maximum heart temperature at block B occurred at 50.7 °C for 48 hours, the maximum cardiac temperature difference It is 15.8 ° C. Both methods are in compliance with the specifications.

APA, Harvard, Vancouver, ISO, and other styles

37

CHANG, YUNG-CHING, and 張泳清. "Different types of chemical admixture in the application of high performance concrete results analysis." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/m6ny5t.

Full text

Abstract:

碩士
正修科技大學
營建工程研究所
104
Chemical doping agent is one of essential raw materials: concrete, and concrete is the most traditional engineering materials, almost all engineering are required to use concrete, but concrete shall be parous, transport, pumping, cast on site, maintenance and other multiple operations, caused the quality is not easy to control and easy to have unstable situation. In order to overcome the bad influence of the construction of concrete construction, the quality of the product quality is introduced, and the high performance concrete is introduced to meet the environmental protection and reduce the man-made factors. High fluidity concrete is one kind of high performance concrete and its subsequent evolution modified into self compacting concrete, bridges in our country has many uses more easily placing self filling concrete (SCC) case, especially the bridge pier structure. Discrimination in self filling concrete in domestic application is widely used, this study adopts elevated road project in Kaohsiung harbor couplet outside the approved design strength 350kgf/cm2 self compacting concrete, in the same proportion change G type lignin sulfonic acid series water reducing retarder, can provide liquidity high slump flow mixed concrete special agent and a carboxylic acid polymer, a new generation of mobile agent to do different types of pharmaceutical and adding different dosage and view the results. It is suggested that different types of pharmaceutical suitability of concrete.

APA, Harvard, Vancouver, ISO, and other styles

38

Liao, Chan-Chang, and 廖展章. "Assessment Concrete Durability For Different Mineral Admixture Contant By Using Acceleration Chloride Migration Test." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/33904769293923418047.

Full text

Abstract:

碩士
國立臺灣海洋大學
材料工程研究所
92
The accelerated chloride migration test (ACMT) was used to investigate the effect of mineral admixtures on the resistance of chloride ion penetration in concrete. Testing variables include the content of fly ash/ground granulated blast-furnace slag and water/binder ratio. Cylindrical specimens with a dimension of 10x20cm were cast for compressive strength test and chloride penetration test. Chloride ion flux and the chloride ion migration coefficient were evaluated using the test data and Nernst-Planck equation. It was found that partial replacement of fly ash/slag for Portland cement in concrete is beneficial for resistance of chloride ion penetration. The optimum percent of replacement is 25% for fly ash and 45% for slag, respectively. Slag replacement is better than fly ash replacement as far as migration coefficient is concerned. And, there is no definite relationship between compressive strength and flux (or chloride migration coefficient).

APA, Harvard, Vancouver, ISO, and other styles

39

林凡皓. "The Optimum Dosage of Self-Curing Admixture for Curing Concrete at Low Relative Humidity." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/33089795702516818188.

Full text

Abstract:

碩士
國立交通大學
土木工程學系
101
Curing is a very important step toward a more durable, higher strength, and less shrinkage concrete. Since sustainability has been the main stream to counteract global warming, supplementary cementitious materials, such as fly ash and slag, have been used widely to partly replace cement. This makes curing even more important. This study is trying to improve the quality of concrete under low relative humidity with various self-curing admixtures(SCA) and dosages. The compressive strengths, volume change, RCPT, and bond strengths were investigated for concrete specimens with and without SCA. It is found that the optimum SCA dosage is 1% of cementitious material. A 3 days wet cure of specimens with SCA showed comparative strength of specimens without SCA under standard curing. For RCPT, a 5 day wet curing of specimens with SCA showed better resistance than standard cured specimens without SCA. The bond strengths of specimens with SCA, regardless of wet curing regime, are better than specimens without SCA and wet-cured for 28 days. The specimens with SCA demonstrated better bond strength compared to the control specimens at all curing regimes. Keywords: concrete, self-curing, wet curing, compressive strength, RCPT, bond

APA, Harvard, Vancouver, ISO, and other styles

40

Chen, Yi-Hsuan, and 陳頤萱. "Effects of Fly Ash with High Calcium Oxide Content on Properties of Concrete Mixtures with Self-Curing Admixture." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/k9hsc5.

Full text

Abstract:

碩士
國立交通大學
土木工程系所
104
Fly ash is a kind of pozzolans. It can react with calcium hydroxide to form the calcium silicate hydrate which fills the pores in concrete. Pozzolanic reaction can improve the quality of concrete, but it is slower than the hydration of cement. This makes curing more important to guarantee the effectiveness of pozzolans, so the development and applications of self-curing admixture (SCA) help for retaining the moisture in concrete and facilitating the pozzolanic reaction. In this study, fly ash with high calcium oxide content was used to replace a part of cement, which aims to discuss the results of SCA using in the different fly ash replacement concrete. A method to increase the calcium oxide and free lime content in fly ash was selected by adding lime powder to the original fly ash in order to vary calcium oxide and free lime content of the fly ash. The basic properties of mortar tests consisted of water requirement, fluidity, initial and final setting time. The mortar tests focus on observing the different amount of calcium oxide content in mortar mixtures with SCA how to influence their basic properties. The concrete tests focus on comparing the differences between using class F fly ash and using fly ash with high calcium oxide content to replace different part of cement in concrete mixtures with SCA. This research showed that SCA is suitable for the concrete with high-calcium oxide-content fly ash. SCA can effectively enhance the curing of the concrete. Using high-calcium oxide-content fly ash in concrete can increase the compressive strength and splitting tensile strength and reduce the water loss and shrinkage. Surface resistivity test showed that the concrete with high-calcium oxide-content fly ash and SCA has good durability. But when it is applied to the concrete with large amount high-calcium oxide-content fly ash replacement, which may cause slump loss or volume stability problems.

APA, Harvard, Vancouver, ISO, and other styles

41

Ganaw, Abdelhamed I., David C. Hughes, and Ashraf F. Ashour. "Grout rheological properties for preplaced aggregate concrete production." 2014. http://hdl.handle.net/10454/7506.

Full text

Abstract:

yes
This paper investigates the effect of cement based grout rheology on the injection process through coarse aggregate for producing preplaced aggregate concrete. Four different sands were used in the grout production at different water-cement ratios and cement-sand ratios. Superplasticiers and pulverised fuel ash were also employed in the grout production. Coarse aggregate of known weight was compacted into 150 mm cubic forms, and then the grout was injected through a plastic pipe under self weight into the stone ‘skeleton’. It has been found that there are threshold values of the rheological parameters beyond which full injection is not possible. In particular, all grout mixes with and without additives and admixtures exhibited the same yield stress threshold value for full injection, whereas the threshold values for other rheological properties including the grout plastic viscosity, flow time and speed were different according to the materials added to the mix.

APA, Harvard, Vancouver, ISO, and other styles

42

I-Horng, Hwang, and 黃一弘. "Bond Stress Distribution along the Splice Length in the High Strength Concrete with Silica Fume Admixture and The Test on Bond Strength of Hot-Dip Galvanized Deformed Bars Embedded in Concrete." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/74208174138507734507.

Full text

Abstract:

碩士
國立臺灣科技大學
營建工程技術學系
86
In normal strength concrete (NSC), distribution of bond stress along the splice length is evenly. This hypothesis had been verified and become a common sense. But in high strength concrete (HSC), different standpoints of views on this hypothesis existed. In this study, the bond stress distribution along the splice length is proposed to be investigated to clear the design concerns of the code. The bond strength of hot-dip galvanized deformed bars are referred to be the same by the ACI building code. Since the lack of test data, above treatment is questionable. The splice bond strength of hot-dip galvanized deformed bars was also investigated in this study. The test variables included the use of silica fume admixture, the compressive strength of concrete, the splice length, the index of stirrup confinement Ktr, and the steel with or without hot-dip galvanizing. Eight beam specimens of HSC with silica fume admixture and four beam specimens with hot-dip galvanized deformed bars are tested. Test results shows that the distribution of splice bond stress of deformed bars is evenly, despite of the NSC or HSC, with or without silica fume, long or short splice length, high or low stirrup confinement over splice region. Test result also shows that the spliced bond efficiency of hot-dip galvanized deformed bars is less than the usual deformed bars and that the average reduction ratio is about 10%.

APA, Harvard, Vancouver, ISO, and other styles

43

吳青陽. "A Study on the Mixture Proportioning Design of Mortar Coefficient Method to Add High Performance Water-reducing Admixture in Porous Concrete(aggregate gradation 19mm~9.5mm)." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/863x33.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

張正明. "A Study on the Mixture Proportioning Design of Mortar Coefficient Method to Add High Performance Water-reducing Admixture in Porous Concrete (aggregate gradation 9.5mm~4.75mm)." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/ju22mz.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

LAI, LEONG MAN, and 梁民禮. "A Study on the Mixture Proportioning Design of Paste Content Ratio Method to Add High Performance Water-reducing Admixture in Porous Concrete (aggregate gradation 19mm~9.5mm)." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/q5sv7s.

Full text

Abstract:

碩士
逢甲大學
土木工程學系
107
The purpose of this study is to find the mixture design that can improve the strength and permeability of porous concrete while maintaining the workability by using the mixture proportioning design of paste content ratio method and adding high-performance water-reducing admixture. In this study, aggregate gradation of size 19mm~9.5mm is used and the design conditions were determined after reference to the previous study. The target porosity was set at 30% and 35%, and the paste content ratio was set at 1.15, 1.25, 1.35. The original water-cement ratio is 0.3, with the addition of high-performance water reducing agent 1%, 1.5%, 2%, a total of 18 sets of mixture proportioning design. Adjust the water-cement ratio through the water-reducing rate test and after the actual mixing, the standard cylindrical and beam specimen were made and then cured for 28 days. After 28 days, conduct water permeability test, ultrasonic test, elastic modulus test, compressive strength test, and flexural strength test. The experimental results show that target porosity, the water reducing rate is directly proportional to the paste content ratio and amount of high-performance water reducing admixture added; the permeability coefficient is directly proportional to the amount of high-performance water reducing admixture added, and is inversely proportional to paste content ratio; the test results are all beyond the specification of 0.01 cm/sec; compressive strength, flexural strength is directly proportional to the paste content ratio and is inversely proportional to the amount of high-performance water reducing admixture added; ultrasonic wave velocity, elastic modulus is directly proportional to the paste content ratio, and is inversely proportional to the amount of high-performance water reducing admixture added; after comprehensive comparative analysis, the results show that the water permeability coefficient is inversely proportional to the compressive and flexural strength. As a reference, the permeability-compressive strength diagram and the permeability-bending strength diagram can provide the engineering industry to select the best mixture proportioning design according to its required compressive strength, flexural strength and water permeability coefficient.

APA, Harvard, Vancouver, ISO, and other styles

46

CHIU, JEN-WEI, and 邱任緯. "A Study on the Mixture Proportioning Design of Paste Content Ratio Method to Add High Performance Water-reducing Admixture in Porous Concrete(aggregate gradation 9.5 mm ~ 4.75 mm )." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/5vj8cn.

Full text

Abstract:

碩士
逢甲大學
土木工程學系
107
In this study, aggregate gradation of size 9.5 mm ~ 4.75 mm is used. After referring to previous studies, the design conditions were determined. The conditions were 30% and 35% of the target porosity, and paste content ratio at 1.15, 1.25 and 1.35. The water-cement ratio is 0.3. 1%, 1.5%, and 2% of high-efficiency water-reducing agent are added, and a control group. A total of 19 sets of mixture proportioning design. Adjust the water-cement ratio through the water-reducing rate test and after the actual mixing, the standard cylindrical and beam specimen were made and then cured for 28 days. After 28 days, conduct water permeability test, ultrasonic test, elastic modulus test, compressive strength test, and flexural strength test. The result shown that the water reduction rate is directly proportional to the paste content ratio, and the amount of high performance water-reducing admixture addition, while inversely proportional to target porosity; the permeability coefficient is directly proportional to the amount of high performance water-reducing admixture addition and target porosity, while inversely proportional to paste content ratio; ultrasonic wave velocity, compressive strength, elastic modulus, flexural strength are directly proportional to the amount of high performance water-reducing admixture addition, while inversely proportional to paste content ratio and target porosity. Taken together, comparative analysis between permeability coefficient and connected porosity, compressive strength and ultrasonic wave velocity, elastic modulus and compressive strength are proportional. On the other hand, permeability coefficient is inversely proportional to ultrasonic wave velocity, compressive strength and flexural strength. At last this study layout two line graphs the one is relationship between permeability coefficient and compressive strength another is permeability coefficient and flexural strength, and expect they can useful for engineers, choosing the most appropriate mix design proportion of the cement for their engineering purposes.

APA, Harvard, Vancouver, ISO, and other styles

47

Jang, Se Hoon. "Identification of Concrete Incompatibilities Using Cement Paste Rheology." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-349.

Full text

Abstract:

The complex interaction between cement and chemical/mineral admixtures in concrete mixtures sometimes leads to unpredictable concrete performance in the field which is generally defined as concrete incompatibilities. Cement paste rheology measurements instead of traditional workability tests (i.e., slump cone test) can have great potential in detecting those incompatibilities in concrete before the concrete is placed, which can, in turn, avoid related workability problems and setting time as well as heat evolution abnormalities. The objectives of the present study were to examine the applicability of the dynamic shear rheometer (DSR) to measure cement paste rheology, and to identify cement and mineral/chemical admixture incompatibilities, based on the determined rheological parameters. The DSR was modified and optimized for cement paste rheology measurements. Two different modes of operations (i.e., static and dynamic methods) with the modified DSR were investigated to measure representative rheological parameters as well as to identify cement and chemical/mineral admixture incompatibility. The conventional plastic viscosity and yield stress are measured in static mode and storage modulus curve, as a function of time, is measured in dynamic mode. The rate of change of plastic viscosity (RPV) as another static rheological parameter and the modeled magnitude parameter ?, from the dynamic rheological method, showed great potentialities as acceptance criteria to identify incompatible mixtures. The heat of hydration data from isothermal conduction calorimeter tests and setting time results for the studied mixtures have strongly supported the rheology based observations as supporting tools. Based on the main tests results, the acceptance criteria were set up using the rheological parameters in accordance with heat of hydration data. This will ultimately help material suppliers, concrete producers, and other users to detect problematic combinations of concrete ingredients before a given concrete mixture is placed.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Admixture(concrete)'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles