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1
Sounthararajan, V. M., and A. Sivakumar. "Pulse Velocity Measurements in Fly Ash Blended Cementitious Systems Containing 43 Grade Cement." ISRN Civil Engineering 2013 (May 27, 2013): 1–7. http://dx.doi.org/10.1155/2013/369387.
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Investigations on the different supplementary cementitious materials based on the hardening properties and the optimized dosage in cementitious systems find the right choice of pozzolanic material. It is essential to combine various additive/admixtures in concrete in proper proportions to maximize the benefits resulting in cost savings in construction. In the recent years, production technology and composition of hydraulic cements affect the setting and early age behavior of cementitious material. The addition of fly ash in cement is one viable technology to derive maximum benefits in terms of the economy and improved pozzolanic reaction. Ultrasonic pulse velocity testing is a feasible method for evaluating the hardening properties of cementitious materials. In this study, an attempt was made to derive the engineering basis for understanding the development of hardness during hydration of fly ash (FA) based cementitious systems. The tests conducted using pulse velocity technique proved to be an effective method for characterizing the early strength gain properties of different cementitious systems.
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Kirakevych, Iryna, Myroslav Sanytsky, and Igor Margal. "Self-Сompacting Сoncretes, which hardening at different temperature conditions." Theory and Building Practice 2020, no. 2 (November 20, 2020): 107–12. http://dx.doi.org/10.23939/jtbp2020.02.107.
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In the article the features of reinforced concrete hardening at different temperature conditions and the current issues of preparation technology of Self-Сompacting Сoncretes (SCC) on the basis of superplasticized cementitious systems, combining knowledge of structure and modifying Portland cement compositions "Portland cement – active mineral additives – microfiller – superplasticizer – accelerator of hardening" to search for rational making provision of technical and building properties of concrete in the changing factors of its composition, technology and exploitation are shown. The physico-chemical peculіarities of hydration and hardening processes of superplasticized cementitious systems were established. The problem of obtaining Self-Compacting mixtures and Rapid-Hardening Concretes on their basis by the direct structure formation of cementitious matrix was solves. The optimization of Self-Compacting Concretes composition on the base of superplasticized cementitious systems with high early strength was carried out. The quality parameters of developed concretes were investigated and the effectiveness of their using in different temperature conditions was shown. The results of the studies found that the use of the superplasticized cementitious systems allows to influence on technological properties and kinetics of structure formation and create concrete structure with improved construction and technical properties at a different temperature conditions. Technological solutions designing of superplasticized cementitious systems that solves the problem of obtaining the Self-Сompacting Сoncretes (SCC) on their basis with using non-vibration technology are established. This creates an opportunity allows to solve the problem of obtaining for enabling early loading, reducing the production cycle, increasing turnover and formwork acceleration of monolithic buildings and structures at different temperature conditions.
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Kirakevych, Iryna, Myroslav Sanytsky, Orest Shyiko, and Roman Kagarlitsky. "MODIFICATION OF CEMENTITIOUS MATRIX OF RAPID-HARDENING HIGH-PERFORMANCE CONCRETES." Theory and Building Practice 2021, no. 1 (June 22, 2021): 79–84. http://dx.doi.org/10.23939/jtbp2021.01.079.
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The paper presents the results of research concerning the peculiarities of modern High Performance Concretes based on cementitious systems "Portland cement – active mineral additives – micro fillers – superplasticizers – accelerators of hardening". Physico-chemical regularities of structure formation of super plasticized cementitious systems are established. It is shown that the formation of secondary fine ettringite due to the interaction of active alumina with calcium hydroxide and gypsum in the non-clinker part of the binder because of the effect of "self-reinforcement" compensates for shrinkage and increases the strength of the cementitious system. The modification of the cementitious matrix makes it possible to obtain Rapid Hardening High Performance Concretes that provide early loading and turnover of the formwork of monolithic constructions.
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Luković, Mladena, Hua Dong, Branko Šavija, Erik Schlangen, Guang Ye, and Klaas van Breugel. "Tailoring strain-hardening cementitious composite repair systems through numerical experimentation." Cement and Concrete Composites 53 (October 2014): 200–213. http://dx.doi.org/10.1016/j.cemconcomp.2014.06.017.
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Park, Wan Shin, Young Il Jang, Hyun Do Yun, Il Seung Yang, and Bae Su Khil. "The Behavior of Pseudo Strain-Hardening Cementitious Composite (PSH2C) Using Synthetic Fibers under Uniaxial Tensile Loading." Key Engineering Materials 627 (September 2014): 449–52. http://dx.doi.org/10.4028/www.scientific.net/kem.627.449.
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The application of pseudo strain-hardening cement composites (PSH2C) to structural systems depends primarily on the tensile response of the materials, which is a direct function of fiber and matrix characteristics, the fiber content or volume fraction. In general, improved response of material is observed with an increase in the fiber volume fraction, as long as the fiber content does not impede mixing. This paper addresses the direct tensile response of pseudo strain hardening cement composites (PSH2C) reinforced with PET fibers, which belongs to a class of discontinuous short fiber reinforced cement based composites characterized by a strain hardening and multiple cracking responses under direct tensile loading. The variables are different types of fibers (PET, PET+PE, PET+PVA).
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Park, Wan Shin, Jeong Eun Kim, Sun Woong Kim, Song Hee Yun, Nam Young Eom, and Hyun Do Yun. "Panel Shear Strength of Steel Coupling Beam-Pseudo Strain Hardening Cementitious Composite Wall Connection." Applied Mechanics and Materials 328 (June 2013): 965–69. http://dx.doi.org/10.4028/www.scientific.net/amm.328.965.
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Hybrid coupled wall systems, where steel coupling beams couple two or more pseudo strain hardening cementitious composite (PSH2C) shear wall can be used in medium and high-rise construction subjected to earthquake. This paper addresses the panel shear strength of steel coupling beams - PSH2C shear wall connection. Test variables included the connection detail in hybrid coupled shear wall system. The results show that Specimens PSH2C-PSFF and PSH2C-PSFFT exhibits greater panel shears strength than Specimen PSH2C-PSF.
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Shang, Xing-yan, Jiang-tao Yu, Ling-zhi Li, and Zhou-dao Lu. "Strengthening of RC Structures by Using Engineered Cementitious Composites: A Review." Sustainability 11, no. 12 (June 19, 2019): 3384. http://dx.doi.org/10.3390/su11123384.
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This paper presents a review of the recent work assessing the performance of building structures strengthened with engineered cementitious composite (ECC). ECC characterizes tensile strain hardening and multiple cracking properties, as well as strong interfacial bonding performance with substrate concrete, which makes it a promising retrofitting material. A lot of researches have been conducted on reinforced concrete (RC) structures, including beams, columns, beam–column joints, and fire-damaged slabs, strengthened with ECC material, and an extensive collection of valuable conclusions were obtained. These strengthening systems usually combine ECC with FRP textiles or steel bars to form a composite strengthening layer. The review demonstrates that ECC strengthening can greatly improve the performance of RC structures.
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Oproiu, Carmen-Lidia, Georgeta Voicu, Alina Bădănoiu, and Adrian-Ionuţ Nicoară. "The Solidification/Stabilization of Wastewater (From a Landfill Leachate) in Specially Designed Binders Based on Coal Ash." Materials 14, no. 19 (September 27, 2021): 5610. http://dx.doi.org/10.3390/ma14195610.
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The aim of this study is to assess the possibility to solidify/stabilize a liquid waste from a municipal waste landfill using binders based on coal ash (fly ash and bottom ash) and specially designed cements for waste treatment (INERCEM). The leaching test proved that all cementitious systems are efficient for the solidification/stabilization of the studied wastes and can reduce the leaching potential of heavy metals present in both liquid waste and coal ash. Therefore, these wastes cease to be a source of environmental pollution. X-ray diffraction (XRD) and thermal complex analysis (DTA-TG) were used to assess the nature and amount of compounds formed in these cementitious systems during the hydration and hardening processes; ettringite, calcium silicate hydrates and CaCO3 were the main compounds formed in these systems assessed by these methods. The microstructure of hardened specimens was assessed by scanning electronic microscopy (SEM); the presence of hydrate phases, at the surface of cenospheres present in fly ash, proved the high pozzolanic reactivity of this phase.
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Cho, Chang-Geun, and Sun-Ju Lee. "Inelastic Responses and Finite Element Predictions of Fiber Cementitious Composite and Concrete Columns." Materials 14, no. 9 (April 24, 2021): 2180. http://dx.doi.org/10.3390/ma14092180.
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In this research, reinforced concrete (RC) and strain-hardening cementitious composite (SHCC) columns subjected to lateral loads combined with a constant load were investigated, both by experiments and predictions, with two distributed inelastic finite element models established by the stiffness and flexibility formulations. SHCC applied in the column plastic hinge region could not only enhance the lateral load and displacement capacities of columns but also offer effective advantages in the control of bending and shear cracks induced by multiple microcracks, the prevention of the spalling of cover concrete, and the resistance to buckling of steel bars. With the layered cross-sectional approach using constitutive laws of SHCC considering a proposed model of the post-cracked high-ductile tensile characteristics, as well as concrete and reinforcing steel bars, an inelastic beam-column finite element model was presented with a distributed flexibility formulation. In comparison with experiments concerning the RC and reinforced strain-hardening cementitious composite (R-SHCC) columns, the current flexibility method showed relatively accurate estimations in the lateral load and displacement responses of column systems as well as in localized nonlinear responses of cross-section as estimated in axial strains of longitudinal reinforcing steel bars. In comparison with the stiffness method, the current flexibility method gave more accurate solutions at both element and structural levels, as manifested in the experiments and analysis solutions.
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Schmidt, Wolfram, Henricus Jozef Hubertus Brouwers, Hans Carsten Kuehne, and Birgit Meng. "Influence of Environmental Temperatures on the Performance of Polymeric Stabilising Agent in Fresh Cementitious Materials." Key Engineering Materials 466 (January 2011): 97–104. http://dx.doi.org/10.4028/www.scientific.net/kem.466.97.
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Stabilising admixtures are commonly used additives in repair mortars and grouts. Beyond this, such type of admixture is increasingly used in concrete and other cementitious materials. In particular when fresh mortar or concrete properties have to be adjusted reliably, stabilising agents can be beneficially used to improve workability and robustness of the mixture. The mode of operation of these admixtures varies, rather affecting either the liquid phase or the solid particles in the dispersion, both causing strong interactions with the mortar or concrete system, and significant changes in their rheological behaviour. Furthermore, these are strongly affected by the environmental temperature during the casting process. In the paper the effect of temperature on the performance of stabilising agents in cementitious systems is presented and how performance changes affect fresh and hardening mortar or concrete properties. Particular attention is placed on interactions between stabilising agents and superplasticizers. Results are discussed with special focus on self-compacting concrete.
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Luković, Mladena, Branko Šavija, Guang Ye, Erik Schlangen, and Klaas van Breugel. "Failure Modes in Concrete Repair Systems due to Ongoing Corrosion." Advances in Materials Science and Engineering 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/9649187.
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Corrosion of steel reinforcement is the main cause of deterioration in reinforced concrete structures. It can result in cracking and spalling of the concrete cover. After the damaged cover is repaired, reinforcement corrosion might continue and even accelerate. While the development of the corrosion cell is difficult to control, the damage can be possibly delayed and controlled by use of a suitable repair material. The lattice fracture model is used in this paper to investigate the performance of strain hardening cementitious composite (SHCC) in concrete repair systems exposed to ongoing corrosion. Numerical results were verified by experimental tests when SHCC, nonreinforced material (repair mortar), and commercial repair mortar are used as repair materials. In experiments, reinforcement bars (surrounded by a repair material) were exposed to accelerated corrosion tests. The influence of the substrate surface preparation, the type of repair material, the interface, and the substrate strength on the resulting damage and failure mode of repair systems are discussed. In general, SHCC repair enables distributed cracking with small crack widths, up to several times smaller compared to repair mortar. Furthermore, more warning signs prior to the final failure are present in the SHCC repair system.
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Tysmans, Tine, and Jan Wastiels. "Editorial on Special Issue “Textile-Reinforced Cement Composites: New Insights into Structural and Material Engineering”." Applied Sciences 10, no. 2 (January 13, 2020): 576. http://dx.doi.org/10.3390/app10020576.
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This special issue presents the latest advances in the field of Textile-Reinforced Cement Composites, including Textile-Reinforced Concrete (TRC), Textile-Reinforced Mortar (TRM), Fabric-Reinforced Cementitious Matrix (FRCM), etc. These composite materials distinguish themselves from other fibre reinforced concrete materials by their strain-hardening behaviour under tensile loading. This Special Issue is composed of 14 papers covering new insights in structural and material engineering. The papers include investigations on the level of the fibre reinforcement system as well as on the level of the composites, investigating their impact and fatigue behaviour, durability and fire behaviour. Both strengthening of existing structures and development of new structural systems such as lightweight sandwich systems are presented, and analysis and design methods are discussed. This Special Issue demonstrates the broadness and intensity of the ongoing advancements in the field of Textile-Reinforced Cement composites and the importance of several future research directions.
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Sanytsky, Myroslav, Tetiana Kropyvnytska, Iryna Нeviuk, Pawel Sikora, and Serhii Braichenko. "Development of rapid-hardening ultra-high strength cementitious composites using superzeolite and N-C-S-H-PCE alkaline nanomodifier." Eastern-European Journal of Enterprise Technologies 5, no. 6 (113) (October 29, 2021): 62–72. http://dx.doi.org/10.15587/1729-4061.2021.242813.
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It is shown that high operational reliability of structural materials, in particular at high temperatures, is achieved through the use of ultra-high strength cement composites. Studies of various types of Portland cements with mineral additives of the CEM II/A type have established that a stone based on Portland cement with superzeolite is the most resistant to high temperatures. It has been proven that due to the "self-autoclaving" effect, the strength of a stone based on CEM II/A-P 42.5 R is 1.2–1.3 times higher than a stone based on other types of CEM II/A. To obtain fast-hardening cement composites, a nanotechnological approach based on the use of sol-gel technology has been implemented. Using the methods of IR spectroscopy, electron microscopy, the fact of obtaining, by the chemical method of synthesis, an alkaline nanomodifier N-C-S-H-PCE, which is a nano–liquid based on nano-core seeds of sodium/calcium hydrosilicates, has been proved. It has been confirmed that the introduction of the alkaline nanomodifier N-C-S-H-PCE provides a significant intensification of the early structure formation processes in the paste based on Portland cement with superzeolite (after 12 hours, 24 hours and 28 days, the strength is 16.9; 30.5 and 104.1 MPa). It has been established that the complex combination of Portland cement with superzeolite, corundum aggregate, basalt fiber and alkaline nanomodifier provides rapid-hardening of ultra-high strength cement composites (T=400 °C) with improved operational properties. Thus, there is reason to assert the feasibility of developing rapid-hardening ultra-high strength cementitious composites. This solves the problems associated with the need to increase their early strength and performance. As a result, it is possible to carry out repair work to protect equipment from abrasive wear at elevated temperatures
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Liao, Wen-Cheng, and Wei-Ru Su. "Implementation of Highly-Flowable Strain Hardening Fiber Reinforced Concrete in New RC Beam-Column Joints." MATEC Web of Conferences 147 (2018): 01003. http://dx.doi.org/10.1051/matecconf/201814701003.
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The purpose of New RC project was aimed to reduce the member sections and increase the available space of high rise buildings by using high strength concrete (f’c > 70 MPa) and high strength rebars (fy > 685 MPa). Material consumptions and member section sizes can be further reduced owing to the upgrade of strength. However, the nature of brittleness of high strength may also cause early cover spalling and other ductility issues. Addition of steel fibers is an alternative as transverse reinforcement. Highly flowable strain hardening fiber reinforced concrete (HF-SHFRC) has excellent workability in the fresh state and exhibits the strain-hardening and multiple cracking characteristics of high performance fiber reinforced cementitious composites (HPFRCC) in their hardened state. The objective of this study is to investigate the feasibility of implementing HF-SHFRC in New RC building systems, particularly for beam-column joints as an alternative of transverse reinforcements. Four full-scale exterior beam-column joints, including two specimens with intensive transverse reinforcements and two specimens made of HF-SHFRC without any stirrup, are tested. Test results show that the HF-SHFRC specimens perform as well as specimens with intensive transverse reinforcements regarding failure mode, ductility, energy dissipation and crack width control. Integration of New RC building systems and HF-SHFRC can assuring construction qualities and further diminish labor work and give infrastructure longer service life, and eventually lower the life-cycle cost.
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Oproiu, Carmen, Georgeta Voicu, Adrian Ionut Nicoara, and Alina Ioana Badanoiu. "The Influence of Partial Substitution of Raw Materials with Heavy Ash on the Main Properties of Portland Cements." Revista de Chimie 69, no. 4 (May 15, 2018): 860–63. http://dx.doi.org/10.37358/rc.18.4.6216.
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The use of wastes in cement industry have impact both from economic and environmental point of views. Wastes can be used in clinker manufacture (to substitute raw materials or as alternative fuel) as well as supplementary cementitious materials in cement. This paper presents results regarding the use of heavy ash (bottom ash) as component of raw mix used for the clinker manufacture. Two types of cements were obtained by the milling of clinker produced with/without heavy ash (HA) as component of raw mix and gypsum (2%). The compressive strengths of these cements was assessed on plastic mortars (water:binder = 1:2 ratio and binder:aggregate = 1:3 ratio), cast in prismatic moulds (14x14x160 mm3), hardened different periods of time comprised between 1 to 28 days. The hydration and hardening processes which occur in the cementitious systems with/without waste content were assessed on pastes with water to binder ratio of 0.5, hardened for 1 up to 90 days. X-ray diffraction (XRD) and complex thermal analysis (DTA-TG) were used for pastes� characterization. The composition of clinker was assessed by XRD and microstructure by scanning electron microscopy (SEM). The results obtained in the framework of this research do not show any important difference between the clinkers� characteristics produced with alternative raw material (heavy ash) as compared with the ones produced with natural raw materials. Also, the properties of cements produced of these clinkers are similar.
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Fan, Wei, Yan Zhuge, Xing Ma, Christopher W. K. Chow, Nima Gorjian, Jeong-A. Oh, and Weiwei Duan. "Durability of Fibre-Reinforced Calcium Aluminate Cement (CAC)–Ground Granulated Blast Furnace Slag (GGBFS) Blended Mortar after Sulfuric Acid Attack." Materials 13, no. 17 (August 29, 2020): 3822. http://dx.doi.org/10.3390/ma13173822.
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Concrete wastewater infrastructures are important to modern society but are susceptible to sulfuric acid attack when exposed to an aggressive environment. Fibre-reinforced mortar has been adopted as a promising coating and lining material for degraded reinforced concrete structures due to its unique crack control and excellent anti-corrosion ability. This paper aims to evaluate the performance of polyethylene (PE) fibre-reinforced calcium aluminate cement (CAC)–ground granulated blast furnace slag (GGBFS) blended strain-hardening mortar after sulfuric acid immersion, which represented the aggressive sewer environment. Specimens were exposed to 3% sulfuric acid solution for up to 112 days. Visual, physical and mechanical performance such as water absorption ability, sorptivity, compressive and direct tensile strength were evaluated before and after sulfuric acid attack. In addition, micro-structure changes to the samples after sulfuric acid attack were also assessed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to further understand the deterioration mechanism. The results show that overall fibre-reinforced calcium aluminate cement (CAC)-based samples performed significantly better than fibre-reinforced ordinary Portland cement (OPC)-based samples as well as mortar samples in sulfuric acid solution in regard to visual observations, penetration depth, direct tensile strength and compressive reduction. Gypsum generation in the cementitious matrix of both CAC and OPC-based systems was the main reason behind the deterioration mechanism after acid attack exposure. Moreover, laboratory sulfuric acid testing has been proven for successfully screening the cementitious material against an acidic environment. This method can be considered to design the service life of concrete wastewater pipes.
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Thirumurugan, S., and A. Sivakumar. "Synergistic Interaction of Polypropylene Fibres in Latex Modified High Strength Concrete." Archives of Civil Engineering 59, no. 3 (September 1, 2013): 321–35. http://dx.doi.org/10.2478/ace-2013-0018.
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Abstract Synthetic polymer latexes, such as styrene-butadiene rubber (SBR) latex addition in Portland cement has gained wider acceptance in many applications in the construction industry. Polymer-modified cementitious systems seals the pores and micro cracks developed during hardening of the cement matrix, by dispersing a film of polymer phase throughout the concrete. A comprehensive set of experimental test were conducted for studying the compressive properties of SBR latex polymer with crimped polypropylene fibres at relative volume fractions of 0.1 and 0.3%. The results indicated that the addition of polypropylene fibre has little effect on the reduction in the workability of concrete composite containing fly ash and SBR Latex. Increase in polypropylene fibres upto 0.3% Vf showed increase in compressive strength upto 57.5MPa. The SBR concrete without fibre showed an increase in strength upto 20 % compared to plain concrete. Test results also indicated that the compressive strength was increased in SBR fibre concrete by means of an ordinary dry curing process than wet curing because of their excellent water retention due to polymer film formation around the cement grains. On the contrary the compressive strength reduces for SBR fibre concretes under wet curing compared to dry curing
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Kothari, Ankit, Karin Habermehl-Cwirzen, Hans Hedlund, and Andrzej Cwirzen. "A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete." Materials 13, no. 16 (August 6, 2020): 3467. http://dx.doi.org/10.3390/ma13163467.
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Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.
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Jędrzejczak, Patryk, Łukasz Ławniczak, Agnieszka Ślosarczyk, and Łukasz Klapiszewski. "Physicomechanical and Antimicrobial Characteristics of Cement Composites with Selected Nano-Sized Oxides and Binary Oxide Systems." Materials 15, no. 2 (January 16, 2022): 661. http://dx.doi.org/10.3390/ma15020661.
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In recent years, increasing attention has been paid to the durability of building materials, including those based on cementitious binders. Important aspects of durability include the increase of the strength of the cement matrix and enhancement of material resistance to external factors. The use of nanoadditives may be a way to meet these expectations. In the present study, zinc, titanium and copper oxides, used in single and binary systems (to better the effect of their performance), were applied as additives in cement mortars. In the first part of this work, an extensive physicochemical analysis of oxides was carried out, and in the second, their application ranges in cement mortars were determined. The subsequent analyses were employed in determining the physicochemical properties of pristine oxides: Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray fluorescence (EDXRF), scanning electron microscopy (SEM), measurement of the particle size distribution, as well as zeta potential measurement depending on the pH values. Influence on selected physicomechanical parameters of the cement matrix and resistance to the action of selected Gram-positive and Gram-negative bacteria and fungi were also examined. Our work indicated that all nanoadditives worsened the mechanical parameters of mortars during the first 3 days of hardening, while after 28 days, an improvement was achieved for zinc and titanium(IV) oxides. Binary systems and copper(II) oxide deteriorated in strength parameters throughout the test period. In contrast, copper(II) oxide showed the best antibacterial activity among all the tested oxide systems. Based on the inhibitory effect of the studied compounds, the following order of microbial susceptibility to inhibition of growth on cement mortars was established (from the most susceptible, to the most resistant): E. coli < S. aureus < C. albicans < B. cereus = P. aeruginosa < P. putida.
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Guades, Ernesto, Henrik Stang, Gregor Fisher, and Jacob Schmidt. "Hybrid fibre-reinforced geopolymer (HFRG) composites as an emerging material in retrofitting aging and seismically-deficient concrete and masonry structures." MATEC Web of Conferences 289 (2019): 04003. http://dx.doi.org/10.1051/matecconf/201928904003.
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Fibre-reinforced polymer (FRP) systems have recently become popular in repairing concrete or masonry structures because of their inherent advantages. In spite of these benefits, FRPs have drawbacks having low fire resistance, poor environmental sustainability and incompatibilty with the substrate concrete. The effort to address these issues has led to the development of an emerging strain hardening cementitious (SHC) material using an inorganic polymer known as hybrid fibre-reinforced geopolymer (HFRG) composites. Compared with cement-based SHC composites, HFRG has better bond performance to concrete substrates, higher fire resistance, greater corrosion durability and helps to reduce CO2 emissions. This paper reviews the recent development of HFRG composites as an emerging repair material. Literature reveals that flowability of a fresh HFRG mixture decreases with increasing fibre content though still workable up to 2% fibre volume. Fibre synergy could result in 10–181% higher flexural toughness of geopolymer composites than when just using mono fibres. The application of HFRG composites to RC beams increased displacement ductility by to 263%. To date, there has been no reported field application of HFRG as a repair material though mono-fibre FRG has been field-applied as a strengthening material in large-diameter sewer RC pipes, RC culverts, RC sewerage manholes and dam surface improvement.
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Donkor, Peter, Esther Obonyo, and Christopher Ferraro. "Fiber Reinforced Compressed Earth Blocks: Evaluating Flexural Strength Characteristics Using Short Flexural Beams." Materials 14, no. 22 (November 16, 2021): 6906. http://dx.doi.org/10.3390/ma14226906.
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There are ongoing research efforts directed at addressing strength limitations of compressed earth blocks (CEB) that inhibit their deployment for structural applications, particularly in areas where masonry systems are regularly subjected to lateral loads from high winds. In this paper, the authors focus specifically on the extent to which polypropylene (PP) fibers can be used to enhance the flexural performance of CEB. Cementitious matrices used for CEB production exhibit low tensile and flexural strength (brittle) properties. This work investigates plain (unreinforced) and fiber-reinforced specimens (short flexural beams) with fiber mass content of 0.2, 0.4, 0.6, 0.8, and 1.0% and ordinary Portland cement (OPC) content of 8%. The influence of the inclusion of fiber was based on tests conducted using the Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete (ASTM C1609). Material properties that were quantified included first-peak strength, peak strength, equivalent flexural strength, residual strength, and flexural toughness. There was an observed improvement in the performance of the soil-fiber matrixes based on these results of these tests. It was also observed that when the fiber content exceeded 0.6% and above, specimens exhibited a deflection- hardening behavior; an indication of improvement in ductility. An equivalent flexural strength predictive model is proposed.
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Aiello, Maria Antonietta, Alessio Cascardi, Luciano Ombres, and Salvatore Verre. "Confinement of Masonry Columns with the FRCM-System: Theoretical and Experimental Investigation." Infrastructures 5, no. 11 (November 16, 2020): 101. http://dx.doi.org/10.3390/infrastructures5110101.
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Fabric Reinforced Cementitious Matrix (FRCM) systems are promising solutions for the confinement of masonry columns because they demonstrate strengthening effectiveness and, at the same time, compatibility with historical substrates. Nevertheless, the matrix is responsible for the stress-transfer from the structural element to the fabric-reinforcement. Therefore, in the case of poor-quality mortar, the effectiveness of the strengthening can be limited or even compromised. On the other hand, the low content of fibers utilized for FRCM systems generally involves the need to apply more layers in order to accomplish design requirements and a continuous configuration of the reinforcement is more often addressed. Few experimental and theoretical investigations have been targeted to the before mentioned aspects in the recent past, namely the influence of the kind of mortar, the number of layers, and the strengthening configuration (continuous, discontinuous) on the effectiveness of confinement. The present paper refers to the results of an experimental investigation on FRCM confined clay brick masonry. A series of small-scale masonry columns were tested under monotonic centered load until collapse. The varied parameters were the number of confining layers (i.e., 1, 2, and 3) and the confinement configuration (i.e., continuous and discontinuous). The performed research aims to contribute in strengthening to the knowledge in the field of FRCM-confinement, mainly focusing on some of the mentioned unexplored aspects (number of layers, strengthening configuration) that could be considered for validation/improvement of analytical design-oriented formulas. In particular, some analytical models, available in the technical literature, were adopted for predicting the herein reported experimental results. Even if based on few experimental results, the outcomes showed that the number of FRCM-layers and the confinement configuration were crucial parameters affecting the confining effectiveness. The compressive strength was satisfactorily predicted in all cases by the two available utilized models. On the other hand, an improvement in the utilized AOM model is suggested in order to include the stress–strain curves of the hardening type.
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Shoshin, Evgeny A., Valeria V. Strokova, and Zheng Mao Ye. "Comparative Assessment of Effectiveness of Calcium Silicate Dispersions Produced Using Sucrose and Lactose as Components of Composite Cement Binder." Materials Science Forum 1017 (January 2021): 11–20. http://dx.doi.org/10.4028/www.scientific.net/msf.1017.11.
Full textAbstract:
Silicate micro- and nano-additives are multifunctional in relation to cement systems. Their application can solve a wide range of technological problems while maintaining the economic efficiency of technical solutions. The effect of silicate additives and fillers is determined by their level of dispersion, due to which the technologies for producing nano- and submicro-sized dispersed materials are being developed. The combination of mechanochemical synthesis of modified calcium hydrosilicates with subsequent thermolysis makes it possible to produce calcium silicate dispersions (SCD), which differ in polymodality of the fractional composition including submicro (10–7–10–6 m) and microdimensional (≥10–6 m) modes. The main element of the technology is the use of modifying carbohydrate, which acts as a stabilizer of hydrated phases of silicates. A comparative study of SCD produced using sucrose (sSCD) and lactose (lSCD) revealed the effect of these carbohydrates on the properties of sSCD and lSCD, as well as their effectiveness as a component of cementitious composite binder. It was found that the level of adsorption of modifying carbohydrate determines the physical properties of SCD (granulometry, specific surface area). The relatively high residual content of free sucrose (0.24%) in the composition of sSCD prevents the consolidation of silicates nanoparticles formed during the thermolysis, causes a high content of submicro sized fractions and a high specific surface area with sSCD (26.3 ± 0.7 m2/g). Lactose is absorbed by the silicate phase; the residual content of free lactose does not exceed 0.028% of lSCD. The low content of stabilizing carbohydrate contributes to the development of nanoparticle consolidation, a decrease in the specific surface area of lSCD to 13.0 ± 0.2 m2/g and content of submicrosized fractions. The residual content of free carbohydrates and particle size characteristics of sSCD and lSCD determine the nature of their influence on Cement-SCD-based concrete setting and hardening. The presence of residual sucrose in the composition of sSCD and fine fractions determines the competitive nature of the processes of retardation of hardening and acceleration of hardening of the cement system due to the nucleation effect, as a result of which the curve of the setting time is extreme. In addition, the inhibitory effect of sucrose reduces the strength of concrete on the 7th day. By the 28th day, the inhibitory effect of sucrose has been overcome, and concrete samples demonstrate an 18% increase in compressive strength with a sSCD content of 30%. The low content of residual free lactose in the composition of lSCD causes the nucleation effect. As a result, there is a monotonous reduction in the setting time of concrete mix with an increase in the content of lSCD in the composition of HF, as well as a significant increase in concrete strength (up to 127%) on the 7th day. At the same time, on the 28th day the strength of concrete increases slightly
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Shoshin, Evgeny A., Valeria V. Strokova, and Zheng Mao Ye. "Comparative Assessment of Effectiveness of Calcium Silicate Dispersions Produced Using Sucrose and Lactose as Components of Composite Cement Binder." Materials Science Forum 1017 (January 2021): 11–20. http://dx.doi.org/10.4028/www.scientific.net/msf.1017.11.
Full textAbstract:
Silicate micro- and nano-additives are multifunctional in relation to cement systems. Their application can solve a wide range of technological problems while maintaining the economic efficiency of technical solutions. The effect of silicate additives and fillers is determined by their level of dispersion, due to which the technologies for producing nano- and submicro-sized dispersed materials are being developed. The combination of mechanochemical synthesis of modified calcium hydrosilicates with subsequent thermolysis makes it possible to produce calcium silicate dispersions (SCD), which differ in polymodality of the fractional composition including submicro (10–7–10–6 m) and microdimensional (≥10–6 m) modes. The main element of the technology is the use of modifying carbohydrate, which acts as a stabilizer of hydrated phases of silicates. A comparative study of SCD produced using sucrose (sSCD) and lactose (lSCD) revealed the effect of these carbohydrates on the properties of sSCD and lSCD, as well as their effectiveness as a component of cementitious composite binder. It was found that the level of adsorption of modifying carbohydrate determines the physical properties of SCD (granulometry, specific surface area). The relatively high residual content of free sucrose (0.24%) in the composition of sSCD prevents the consolidation of silicates nanoparticles formed during the thermolysis, causes a high content of submicro sized fractions and a high specific surface area with sSCD (26.3 ± 0.7 m2/g). Lactose is absorbed by the silicate phase; the residual content of free lactose does not exceed 0.028% of lSCD. The low content of stabilizing carbohydrate contributes to the development of nanoparticle consolidation, a decrease in the specific surface area of lSCD to 13.0 ± 0.2 m2/g and content of submicrosized fractions. The residual content of free carbohydrates and particle size characteristics of sSCD and lSCD determine the nature of their influence on Cement-SCD-based concrete setting and hardening. The presence of residual sucrose in the composition of sSCD and fine fractions determines the competitive nature of the processes of retardation of hardening and acceleration of hardening of the cement system due to the nucleation effect, as a result of which the curve of the setting time is extreme. In addition, the inhibitory effect of sucrose reduces the strength of concrete on the 7th day. By the 28th day, the inhibitory effect of sucrose has been overcome, and concrete samples demonstrate an 18% increase in compressive strength with a sSCD content of 30%. The low content of residual free lactose in the composition of lSCD causes the nucleation effect. As a result, there is a monotonous reduction in the setting time of concrete mix with an increase in the content of lSCD in the composition of HF, as well as a significant increase in concrete strength (up to 127%) on the 7th day. At the same time, on the 28th day the strength of concrete increases slightly
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Rutzen, Matthias, Michael Schulz, Judith Moosburger-Will, Philipp Lauff, Oliver Fischer, and Dirk Volkmer. "3D printing as an automated manufacturing method for a carbon fiber-reinforced cementitious composite with outstanding flexural strength (105 N/mm2)." Materials and Structures 54, no. 6 (November 29, 2021). http://dx.doi.org/10.1617/s11527-021-01827-2.
Full textAbstract:
AbstractAs research interest in the additive manufacturing of cementitious materials for structural uses has been continuously increasing, the question of how to incorporate tensile reinforcement in an automated process has gained further importance. Our research describes a carbon fiber-reinforced cementitious composite produced by common extrusion techniques applied in 3D printing as a means to effectively control fiber alignment. Optimization of the mixture design and consistency allows for admixing up to 3 vol.-% chopped carbon fibers, leading to specimens that can reach a flexural strength exceeding 100 N/mm2 without the addition of further continuous reinforcement. Fiber integrity during the process was checked using optical microscopy. Analysis of the microstructure shows that approximately 70% of the fibers are aligned within ± 5° of a preferential direction. Micromechanical single-fiber push-out tests confirm an interfacial fracture toughness typical for strain-hardening systems. The first insights into a ‘lost formwork’ approach commonly employed in 3D printing show that the reinforcement remains effective even when combined with nonreinforced mortar.
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Huseien, Gassan Fahim, Jahangir Mirza, Nur Farhayu Ariffin, and Mohd Warid Hussin. "SYNTHESIS AND CHARACTERIZATION OF SELF-HEALING MORTAR WITH MODIFIED STRENGTH." Jurnal Teknologi 76, no. 1 (August 27, 2015). http://dx.doi.org/10.11113/jt.v76.3688.
Full textAbstract:
Cementitious materials being the most prospective building blocks achieving their absolute strength to avoid the deterioration in the early stage of service life is ever-demanding. Minimizing the labor and capital-intensive maintenance and repair cost is a critical challenge. Thus, self-healing mortars with modified strength are proposed. Lately, self-healing of micro-cracks by introducing bacteria during the formation of mortar or concrete became attractive. Self-healing with polymeric admixtures is considered to be relatively more durable and faster process. Certainly, the self-healing of synthetic polymeric materials is inspired by biological systems, where the damage triggers an autonomic healing response. This emerging and fascinating research initiative may significantly improve the durability and the safety limit of the polymeric components potential for assorted applications. In this work, using epoxy resin (diglycidyl ether of bisphenol A) without any hardener as admixture polymeric-cementitious materials is prepared. These epoxy-modified mortars are synthesized with various polymer-cement ratios subjected to initial wet/dry curing (WDC) together with long term dry curing (DC). Their self-healing function and hardening effects are evaluated via preloading and drying of the specimens, chemical analysis, and ultrasonic pulse velocity testing. It is demonstrated that 10% of polymer is the best proportion for polymer-cement ratio. Furthermore, the wet/dry curing is established to be superior process for healing hairline cracks present in the mortar. The excellent features of the results suggest that our novel method may constitute a basis for improving the compressive strength and self-healing features of mortars.