Dissertations / Theses on the topic 'Pozzolanic Reactions'

The improvement in the impermeability of concrete was studied using different methods. The main aim was to investigate impermeability improvement of concrete and to compare these methods. Two different methods were examined to investigate and compare impermeability and strength improvement of concrete by using two different sets of concrete specimens. These methods included the application of coating materials to concrete and the production of concrete using different constituent amounts and types. The first set of concrete specimens was prepared by applying two different coating materials (a coating material including both powder and liquid components
and a coating material including only a liquid component) on reference concrete specimens separately. The second set of concrete specimens was prepared using different proportions of concrete constituents such as cement, water, steel and plastic fibers, mineral and chemical concrete admixtures. Various tests were conducted on both sets of concrete specimens in order to compare the permeability of concrete specimens. However, some of these tests v were not applied on all of the specimens because of test and material specifications. The tests were used to evaluate compressive strength, water absorption, chloride ion penetration and depth of water penetration under pressure. These test methods were carried out on concrete cube specimens and concrete cores taken from those specimens according to the relevant standards. It was found that the permeability of the concrete specimens decreased significantly when the coating material which was composed of the combination of powder and liquid components was applied on concrete specimens. However, permeability did not decrease significantly for concrete specimens coated with the coating material composed of only a liquid component. Significant improvement in the impermeability of the concrete specimens was observed when the amount of cement was increased, the water-to-cement ratio was decreased, mineral admixtures (silica fume and fly ash) and plasticizers were used. This improvement was associated with densification of the concrete microstructure and reduction in capillary pores as a result of pozzolanic reaction and due to reduction in water-to-cement ratio. Coating materials were determined to be effective for concretes with high permeability prior to coating whereas their effect was less significant for lower-initial permeability concretes. Moreover, the effect of coating materials on permeability differed depending on their chemical compositions. The effect of using steel fibers and plastic fibers for the improvement of concrete impermeability was found to be insignificant.

Esta pesquisa trata da estabilização de misturas de agregados reciclados por meio da ativação de seus finos, cujas composições possibilitam a ocorrência de reações químicas de cimentação. Para o desenvolvimento da pesquisa foram utilizados dois tipos de agregados reciclados: um proveniente de resíduo de demolição de natureza cimentícia e outro da indústria de cerâmica vermelha. O uso dos materiais foi feito por meio de dosagens para obtenção de misturas cujas combinações de materiais pudessem, quimicamente, potencializar a ocorrência de hidratação do cimento anidro existente nos finos do agregado reciclado cimentício e de reação pozolânica pela pozolanicidade da cerâmica vermelha. Com isso foram obtidas cinco misturas, compostas pelos agregados reciclados em estudo misturados entre si e com a adição de aglomerantes hidráulicos, sobre as quais foram realizados ensaios em laboratório para verificação da ocorrência das reações químicas esperadas com consequente estabilização das misturas, de modo a influenciar nos respectivos comportamentos mecânicos. Também foi realizada a avaliação de características do empacotamento dos grãos como forma de verificar se o arranjo físico, neste caso, exerce influência significativa na melhora do comportamento mecânico das misturas estudadas. Os resultados obtidos indicaram que, de fato, ocorreram as reações químicas esperadas, comprovadas pelos resultados dos ensaios de termogravimetria e difração de raios x, realizados em três diferentes idades de cura. Verificou-se, também, a melhora no comportamento mecânico das misturas por meio do aumento da resistência à compressão simples e do módulo de resiliência com a evolução da cura, além de baixa deformabilidade aos 91 dias de cura. Com isso foi comprovada a estabilização das misturas em estudo, com a consequente melhora de seus desempenhos, sendo devida, principalmente, à ocorrência das reações químicas de hidratação do cimento anidro e pozolânica. A pesquisa demonstrou a possibilidade de se estabilizar misturas de agregados reciclados cimentícios e de cerâmica vermelha por meio da ocorrência de reações químicas de cimentação promovidas pela combinação destes materiais.
This research deals with the stabilization of mixtures constituted by recycled aggregates through the activation of its fines portions, whose components enable the occurrence of chemical cementation reactions. In order to develop this research, two types of recycled aggregates were used: one from demolition waste with cementitious origin, and the other one from the red ceramic industry. The use of these materials was done through mix designs to obtain mixtures whose combinations of materials could chemically increase the occurrence of hydration of the anhydrous existing in fine portion of the recycled cementitious aggregates, and pozzolanic reactions due to the pozzolanicity of red ceramics. Thus, five mixtures were obtained, and they were composed by the studied recycled aggregates, mixed together and with the addition of hydraulic binders, on which laboratory tests were performed in order to verify the occurrence of the expected chemical reactions with consequent stabilization of the mixtures, in order to influence their mechanical behavior. Furthermore, it was performed the evaluation of packing characteristics of the particles to verify if the physical arrangement, in this case, has any significant influence on improving the mechanical behavior of the mixtures studied. The results obtained indicated that in fact the expected chemical reactions occurred, which was verified by the results from thermogravimetry and X-ray diffraction tests performed at three different times of curing. The improvement of the mixtures mechanical behavior by increasing of their compressive strength and their resilient modulus was also verified as the mixtures were cured, in addition to low deformability at 91 days of curing. Thus, the stabilization of the mixtures studied was confirmed, which was mainly due to the occurrence of chemical hydration reactions of the anhydrous cement and pozzolanic reactions. The study demonstrated the possibility of stabilizing mixtures of recycled aggregates cementitious waste and red ceramic by the occurrence of cementing chemical reactions promoted by combination of these materials.

This thesis contains two main parts: theoretical and experimental. The theoretical part deals with summarization knowledge of high-volume fly ash (HVFA) concretes. Among others, there are mentioned processes of producing of fly ash, characteristic features and resistance to aggressive environments of HVFA concretes. The theoretical part ends with a suitable example of practical application. In the practical part were tested properties of nine different mixtures containing 40%, 50% and 60% replacement by weight of the cement by fly ash. They were compared with the reference mixtures without fly ash addition. The main endpoints were long-term compressive strength, resistance to aggressive environments, the influence of fly ash on consistency, hydratation temperatures, water absorption and volume changes.

Published Article
Fly Ash is a by-product at thermal power stations, also otherwise known as residues of fine particles that rise with flue gases. An industrial by-product may be inferior to the traditional materials used construction applications, but, the lower the cost of these inferior materials make it an attractive alternative if adequate performance can be achieved. The objective of this study is to evaluate the chemical and physical effectiveness of self-cementing fly ashes derived from thermal power stations for construction applications with combined standards. Using laboratory testing specimens, suitable types of Fly Ashes namely: Kendal Dump Ash, Durapozz and Pozzfill, were tested to the required standards to evaluate the potential properties. All three Fly Ashes have been classified as a Class F Fly Ash, which requires a cementing agent for reactions to take place and for early strength gains in the early stages of the reaction processes. The Fly Ashes conformed to the combination of standards and have shown that the proper reactions will take place and will continue over period of time. The use of fly ash is accepted worldwide due to saving in cement, consuming industrial waste and making durable materials, especially due to improvement in the quality fly ash products.

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This paper examines the impacts of clay mineralogy on the effectiveness of lime stabilisation at different temperatures. A comprehensive experimental programme was conducted to track down the evolution of lime-clay reactions and their durations through monitoring the evolution of strength gain at predetermined times using the Unconfined Compressive Strength (UCS) test. The study examined clays with different mineralogy compositions comprising Na+ Bentonite and Ball (Kaolinite) clay. Four different clays were tested including 100% bentonite, 100% Ball clay and two clay mixtures with ratios of 1:1 and 1:3 by mass of bentonite to Ball clay. All clays were treated using a range of lime content up to 25% and cured for a period of time up to 672 h at two different temperatures of 20 and 40 °C. The results showed that the continuity of the fast phase (stage 1) of strength gain was dependent on the availability of lime in particular at the higher temperature. Whereas, for the same lime content, the duration of the fast phase and the kinetic of strength gain were significantly related to the clay mineralogy and curing temperature. Except for the initial strength gain at 0 h curing time, the lime-treated Ball clay specimens at 20 °C appeared to show no strength gain throughout the curing period that extended up to 672 h. However, when curing occurred at 40 °C, the no strength gain stage only lasted for 72 h after which a gradual increase in the strength was observed over the remaining curing period of time. The addition of Bentonite to Ball clay succeeded in kicking off the strength gain after a short period of curing time at both curing temperatures.

Perlite is a volcanic mineral. The latest investigations on ground perlite showed that it is suitable for pozzolanic usage. Thus, it is of vital importance especially for countries rich in perlite such as Turkey. The aim of this study is to investigate the advantages and problems associated with using perlite in concrete and to identify accurate methods and amounts of use for producing durable cementitious mixtures. Within the scope of this study, the alkali-silica reactivity of perlite containing cementitious mixtures were compared using four different methods. Expansion mechanism of the mixtures were tried to be understood by measuring the alkalinity of bath waters. In order to cope with early strength decreases caused by perlite addition, activation of the mixtures by chemical and thermal methods were attempted. It was found that chloride containing chemicals are very effective at later ages and sodium containing chemicals are more effective at early ages. Sodiumhydroxide addition to the perlite containing mixtures was found to be detrimental to both the initial and late-age strengths of mortars. It was concluded that perlite addition generally results in a decrease in alkali-silica expansions. However, the expansion of concrete samples should be investigated comprehensively. Thermal curing at high temperatures resulted in a rapid increase at 1-day strengths, however, for better ultimate strengths lower thermal treatments or no-thermal curing were found to be more effective. Compared to the traditional portland cement concretes, high-volume ground perlite concretes have environmental and economical advantages.

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.

Recycling composite glass with different colours in order to be manufactured into new glass products is at present not economically viable. Therefore, the search for new issues other than stockpile areas or dumping sites could be a serious opportunity. To a certain extent, one of the possible solutions is to use the recycled glass in manufacturing cements and in the preparation of concrete mixtures. However, it is essential to manage the two main behaviours that the glass can have when used in cement-based materials: (1) the use of glass as coarse aggregates reveals harmful behaviour related to alkali-silica reaction; (2) on the other hand, it can result in useful behaviour related to pozzolanic reaction if used as fine particles. Furthermore, the significant alkali content should not be overlooked as their mass corresponds to about 13% of the total mass of the glass and as they may activate the alkali-silica reaction. An experimental programme was conducted to provide answers to the various questions raised about the use of glass in cement-based materials. The first part of this work was primarily devoted to the evaluation of the reactive potential of glass in mortars (alkali and pozzolanic reactions). At this stage, nine classes of glass particles ranging from 3[mu]m to 2.5 mm were considered. Then, fine glass particles were used in order to counteract the negative effect of some classes of coarse aggregates having revealed alkali-reactive behaviour. The second part of this work was performed to study the mechanisms that could explain the behaviours of fine and coarse particles in aqueous and concentrated environments. Different answers have been proposed to explain the observed behaviour in terms of grain sizes of glass.

Předložená magisterská práce se zabývá možným použitím vitrifikovaného lignitového lóžového popele jako náhrada slinku v kompozitních cementech. Byly zkoumány vlivy přidaného vitrifikovaného lóžového popele, jeho jemnosti, alkalických roztoků a jejich koncentrací. Byly připraveny kompozitní cementy v souladu s normou DIN EN 197 – 1. V těchto cementech bylo nahrazeno 30 % slinku vitrifikovaným lóžovým popelem. Konkrétně byly připraveny kompozitní cementy s vitrifikovaným lóžovým popelem o jemnosti 5549 cm2/g a 8397 cm2/g. Dále byly přidány alkalické roztoky hydroxidů a síranů vždy o dvou různých koncentracích, za účelem stimulace pucolánové a/nebo geopolymerní reakce. Mechanické vlastnosti připravených vzorků byly charakterizovány mechanickým testováním na prizmách s rozměry 40×40×160 mm, jak je specifikováno v normě DIN EN 196 – 1. Byla provedena nedestruktivní měření dynamického elastického modulu a destruktivní testovaní na pevnosti v tlaku a v ohybu. Distribuce velikosti částic a chemická analýza vstupních materiálů byla vykonána pomocí laserové granulometrie a rentgenové fluorescence. U zatvrdlých kompozitů bylo dále zkoumáno po 2 a 28 dnech hydratace fázové složení s využitím metody rentgenové difrakce a mikrostruktura s využitím skenovací elektronové mikroskopie. Výsledky ukázaly, že mechanické vlastnosti jsou nezávislé na množství přidaných alkálií stejně jako na jemnosti přidaného vitrifikovaného lóžového popele. Nicméně, znatelně nižší mechanické pevnosti byly pozorovány pro vzorky, které byly aktivovány hydroxidy, pravděpodobně kvůli brzké tvorbě silikátového hydrogelu. Vzorky aktivované sírany nedosáhly pevností jako referenční malta.

博士
國立臺灣科技大學
營建工程系
93
This study tries to analyze the microstructure of HPC containing slag and fly ash, and the following methods are employed: SRA, NMR, MIP, SEM, LOI, Electrical Resistivity and Permeability. The test results show that, at the early age inside the cement paste with fly ash, [SiO2(OH)]-2 ionic bond forms C2SH2(B), and [SiO3(OH)]-3 forms C2SH2(A). Afwillite (one kind of C-S-H). Since the Ca2+ ion sticks on the surface of fly ash particle, causing the spoiling effect, the Ca2+ content is reduced and then the forming of nuclide is delayed. On the other side, fly ash and C3A can produce a hexagonal-layered protection which helps put off the hydration of C3A, and therefore there is no hydration product for C2S, C3A and C4AF. By the test of SRA and those of NMR, MIP, SEM, Electrical Resistivity and Permeability, the outcomes from macroview and microview both illustrate that the pozzalanic reaction of fly ash and slag can reduce the content of calcium hydroxide to fill the capillary porosity. Thus the microstructure order of the complex material is rearranged, and then the compression strength and resistivity are enhanced. At the same time, the permeability is reduced and more durability is gained.

博士
國立臺灣科技大學
營建工程系
93
This study tries to analyze the microstructure of HPC containing slag and fly ash, and the following methods are employed: SRA, NMR, MIP, SEM, LOI, Electrical Resistivity and Permeability. The test results show that, at the early age inside the cement paste with fly ash, [SiO2(OH)]-2 ionic bond forms C2SH2(B), and [SiO3(OH)]-3 forms C2SH2(A). Afwillite (one kind of C-S-H). Since the Ca2+ ion sticks on the surface of fly ash particle, causing the spoiling effect, the Ca2+ content is reduced and then the forming of nuclide is delayed. On the other side, fly ash and C3A can produce a hexagonal-layered protection which helps put off the hydration of C3A, and therefore there is no hydration product for C2S, C3A and C4AF. By the test of SRA and those of NMR, MIP, SEM, Electrical Resistivity and Permeability, the outcomes from macroview and microview both illustrate that the pozzalanic reaction of fly ash and slag can reduce the content of calcium hydroxide to fill the capillary porosity. Thus the microstructure order of the complex material is rearranged, and then the compression strength and resistivity are enhanced. At the same time, the permeability is reduced and more durability is gained.

Dissertação de mestrado integrado em Engenharia Civil
A indústria do betão gera alguns problemas ambientais e de sustentabilidade associados à incorporação do Cimento Portland, cujo fabrico é, conforme sabido, altamente consumidor de energia e é responsável por cerca de 7% das emissões de CO2 para a atmosfera. As adições minerais Pozolânicas permitem substituir o Cimento, contribuindo com uma quantidade adicional de silicatos de cálcio hidratado (CSH). Para a formação do CSH adicional a pozolana tem de reagir com o hidróxido de cálcio proveniente da hidratação do Cimento, originando a reação pozolânica. Por vezes, para dosagens elevadas de adições minerais, o hidróxido de cálcio pode ser insuficiente para o bom funcionamento da reação pozolânica, situação em que pode ser necessária a sua adição. Esta reação, geralmente, produz uma redução da porosidade do betão, aferindo ao betão maior durabilidade. Esta substituição apresenta inúmeros benefícios, tanto em relação à reologia no estado fresco quanto ao comportamento mecânico no estado endurecido. Neste contexto, desenvolveu-se este trabalho tendo como principal objetivo estudar a incorporação de cal em misturas cimentícias com elevados teores de adições minerais. Concretamente pretende-se analisar o efeito da incorporação de cal como potencial ativador da reação pozolânica em misturas com quantidades reduzidas de Cimento. Adicionalmente, pretende-se, também, determinar se a adição de cal permite, ou não, dotar a composição de uma maior reserva alcalina e, assim, melhorar a sua resistência à carbonatação. Para isto, realizaram-se doze tipos de composições cimentícias com dois tipos de matriz ligante, Cimento e Cinzas volantes; e Cimento, Cinzas volantes e Metacaulino. Em todas as composições, a quantidade de substituição de Cimento por adições minerais foi de, pelo menos, 60%. Para cada um destes dois tipos de matrizes cimentícias fez-se variar o teor de cal entre 0 e 25%. Neste trabalho experimental, para a mistura ternária, observou-se uma melhoria na resistência à compressão e à carbonatação para as misturas com incorporação de cal até 15%. Esta tendência foi acompanhada nas misturas com Cimento e Cinzas volantes, onde a resistência à compressão, perto da ultima data de ensaio (90 dias), aumentou relativamente à da amostra Padrão para um teor de Cal de 5% e a resistência à Carbonatação foi melhorada independentemente do teor de cal adicionada.
The concrete industry generates some environmental and sustainability issues associated with the incorporation of Portland cement, whose manufacture is, as well known, highly energy consumer and responsible for about 7% of CO2 emissions into the atmosphere. The Pozzolanic mineral additions allow substitute the cement, contributing with an additional amount of hydrated calcium silicate (CSH). For the formation of the additional CSH, the pozzolan must react with the calcium hydroxide from the hydration of the cement, resulting in the pozzolanic reaction. Sometimes, for high dosages of mineral additions, calcium hydroxide may be insufficient for proper functioning of the pozzolanic reaction, situation in which may be necessary its addition. This reaction, usually, produces a decrease in the porosity of the concrete, assessing the concrete a bigger durability. This substitution has many benefits, for the rheology in fresh state as well as the mechanical behavior in the hardened state. In this context, this work was developed with the main objective of studying the incorporation of lime in cementitious mixtures containing large amounts of mineral additions. Specifically, it is intended to analyze the effect of the incorporation of lime as a potential activator of the pozzolanic reaction in mixtures with small quantities of cement. Additionally, the aim was also to determine whether the addition of lime allows, or not, to give the composition an increased alkalinity and thus improve its resistance to carbonation. With this purpose, there were made twelve types of cementitious compositions with two types of matrix binder, Cement and fly ash, and cement, fly ash and Metakaolin. In all compositions, the amount of cement replacement by mineral additions was, at least, 60%. For each of these two types of cementitious matrixes was used a variation of the content of lime between 0 and 25%. In this experimental work, for the ternary blend, we observed an improvement in the resistance to the compressive strength and the carbonation for the blends incorporating lime up to 15%. This tendency was accompanied in mixtures with cement and fly ash, where the compression resistance near the last day of the test (90 days) increased compared to that of the standard sample for a content of 5% of lime, and the resistance to carbonation was improved independently of the amount of lime added.

碩士
國立中央大學
環境工程研究所
89
This study investigated the pozzolanic reactions and engineering properties of slag blended cements (SBC). In this work, SBCs were prepared by blending slag, which was generated from the melting of municipal solid waste incinerator fly ash (referred to as MSWFS), with five types of cements, respectively. Major cement constituents such as C3S (i.e., 3CaO.SiO2) and C3A (i.e., 3CaOAl2O3) were also used alternatively in replacement of cement for contrast. The experiments were divided into three parts: (1) characterization of the slag prepared by melting the MSW incinerator fly ash at 1400℃ for 30 min; (2) assessment of the pozzolanic reaction in the SBC pastes incorporating C3S and C3A with blend ratio ranged from 10% to 40% at various curing ages; and (3) evaluation of the effects of slag on pozzolanic reaction in the SBC pastes for five cements at various curing ages, focusing on their compressive strength, hydration heat behavior, hydration degree, crystalline speciation, and variation of microstructure. The results showed that lower hydration heat of C3S and C3A samples with the incorporation of MSWFS was observed, possibly due to the partial replacement of the mineral constituents by the slag with less activity. In general, the incorporation of slag into C3S and C2S, respectively, decreased the initial hydration reaction whereas increased the pozzolanic reaction at later stage by consuming CH to form CSH and CAH. This was evidenced by the DTA results, which showed a delayed transformation of C3A from C4AH13 to C3AH6. Moreover, hydration degree and the average length of C-S-H, (i.e., the number of Si of linear poly silicate anions in C-S-H gel, Psi) as determined by applying nuclear magnetic resonance (NMR) techniques also indicated a delayed initial hydration and an enhanced later pozzolanic reaction. In the C3S-slag paste, the Psi value increased with increasing curing age as compared with that of the C3S paste. The results of x-ray powder diffractometer (XRPD) revealed that the pozzolanic reaction in C3S-slag paste was mainly affected by the Si2+ and Al3+ released by the slag. On the other hand, the incorporation of slag delayed the initial hydration of C3A in C3A-slag paste, and decreased the formation of ettrigite (AFt) and monosulfoaluminate (AFm) in C3A-gypsum-slag paste. The early unconfined compressive strength (UCS) of SBC pastes for five types of cement were found to decreased with increasing slag blend ratio, whereas the later strength increased. In addition, the UCS for all types of SBC pastes tested with slag blend ratio<20% outperformed that of their pastes without slag. Moreover, the results of mercury intrusion porosimetry (MIP) analysis indicated that the total and the capillarity pore volume decreased with increasing ages, whereas the gel pore volume increased, showing the later pozzolanic nature of the pulverized fly ash slag.

碩士
國立中央大學
土木工程研究所
94
The study is mainly concerning with pyrex glass､coastal range andesites and Heping river aggregate, taking fly-ash slag powder､120 grade and 100grade ground granulated blast furnace slag to replace 0%~55% weight of cement, use of the acceleration mortar test(ASTM C1567)､mortar bar test（ASTM C227） and concrete prism test（ASTM C1293） to evaluate the effect of pozzolan materials mitigates the alkali-aggregate reaction. According to fly-ash slag powder and slag mitigate the alkali-aggregate reaction, we can see the obvious effects that when we use the higher proportion of cement replacement, the better mitigate effect, and the mitigate result would be different because of pozzolan materials change the proportion of the cement、types of pozzolan materials、types of reactive aggregate and alkali content of specimen. According to the testing result of ASTM C1293, when the alkali content Na2Oeq.=2.0%, the specimen of coastal range andesites needs the pozzolan materials to replace 30% of cement and Heping river aggregate needs the pozzolan materials to replace 45% of cement. It can make mitigate dilatability under the endanger threshold value. According to the comparison result of ASTM C1293 and ASTM C1567, we can know that the method of the acceleration mortar test can get pozzolan materials consumption to mitigate effectively alkali-aggregate reaction. If we use actual concrete structure, whether it mitigate usefully the alkali-aggregate reaction. The comparative result is: the testing result of ASTM C1567 is more conservative and the proportion of pozzolan materials is higher. When alkali content of concrete concrete prism test is increasing, the relative of this two tests is increasing. When endanger threshold value of ASTM C1567 is increasing, the consistency of this two tests is increasing. If the extension of the determine harmfulness of ASTM C1567 (age extend from 16 days to 28 days or 56 days), and determine age at 28 days is same as the testing result of ASTM C1293.

碩士
國立臺灣科技大學
營建工程系
103
The electroosmotic chemical treatment has been recently performed by injecting the KOH solution to neutralize the acidic condition after injecting CaCl2 solution at anode area. This could improve the efficiency of injecting W.G. solution in the next stage of treatment, causing the strength of treated soil increased from anode to middle area. However, the strength of middle to cathode area still remained weak. In order to improve it, this study attempt to (1) raising the concentration of CaCl2 solutions to raising amounts of Ca2+ ions and then transport it from anode to the cathode area in next stage of treatment, (2) replacing the acidified W.G. solutions with fresh W.G. solution in the anode compartment to decrease the rate of polymerization, and (3) continually injecting the deionized water to transport the Ca2+ ions from anode to cathode area, also, the high alkaline condition was gradually formed at cathode due to electrolysis and then make the Ca2+ ions accumulated therein. Results indicated that (1) injecting the raised concentration of CaCl2 solution and then injecting KOH solution for neutralization would form a lots of Ca(OH)2 at anode, causing the flow paths of chemical solutions blocked. (2) replacing acidified W.G. solution could raise the efficiency of injecting W.G. solution, thus, the improvement range extended, and (3) injecting the deionized water could transport remained Ca2+ ions from anode to cathode area, simultaneously, forming the highly alkaline condition, causing Ca2+ ions accumulated therein, which finally enhance the efficiency of pozzolanic reaction. Finally, using the previous combination of injecting chemical solutions, besides, replacing the acidified W.G. solution with fresh W.G. solution in the anode compartment per 24 hour, and then continually injecting deionized water, the strength increased 1500% between middle and cathode area and 400% at cathode area, achieving the full strength improvement.

碩士
國立成功大學
土木工程學系碩博士班
90
Abstract Keyword：Efflorescence 、carbonation、pozzolan reaction Efflorescence, a phenomenon of peeling and corrosion that are not only omnipresent in and around the environment we live, nor exclusive to Taiwan, but also a problem that continues to haunt the world over, noticeably without any permanent cure to date. Moreover, fly ash or slag added to cement in a move to save cost, improve the strength and malleability only excel efflorescence of carbonated lime in building structures, which as assessed by EDTA titration, aided by x-ray diffraction together with x-ray microanalysis, in conjunction with phenolphalein tests for carbonation weighing and ultrasound scanned conveyance rates ，twenty-four hours after pouring, the form was removed and the concrete allowed to set for another 24 hours. The concrete was then dipped halfway and allowed to soak for 24 hours under varying environmental conditions had led to the following findings, 1. Where at a water-cement ratio equals to 0.4, efflorescence in cement mixed with fly ash becomes more omnipresent, the higher the content, the more evident efflorescence will become. 2. At relative humidity the higher , and the more content in efflorescence will become. 3. The higher temperature,and the more in efflorescence of content had become increasingly tendency. 4. Cement batch, irrespective of mixing with fly ash or slag, has a noticeably more severe condition of efflorescence accelerated by wind drafts than that without wind drafts. 5. No correlation was established in terms of the amount of efflorescence to the level of carbonation or the oscillation patterns in the ultrasound scan. 6. The experiment also concluded that at a ph rating of 11.1 plus/minus 0.23 detected in efflorescence indicates the concrete has begun to carbonate and the rebar within begun to expand and deteriorate. 7. The higher the content of fly ash or slag, the greater the efflorescence. Thus the ideal mix will contain less fly ash and slag and produce less efflorescence.

碩士
國立中央大學
土木工程研究所
87
This study is to evaluate the environmental effects on inhibition of alkali-aggregate reaction (AAR) by using fly ash and slag to replace a portion of cement and lithium hydroxide. Reactive aggregate, cement adjusted to have different alkali content, and replacement of different portion of cement by fly ash and slag were mixed to make 2.5×2.5×28.5cm concrete prisms. After 28 days initial curing, the prisms were cured in five different environments including containers with 100% relative humidity, soaked in 2.1%, 3.5%, and 4.9% NaCl solutions, as well as in 1N NaOH solution at 38℃. Test results showed that the use of non-reactive aggregate was effective to inhibit AAR even in high alkali content concrete. The use of fly ash to replace more than 20% cement and slag to replace more than 50% cement could inhibit AAR expansion in any environments studied. The effectiveness of AAR inhibition was improved with increasing fly ash and slag replacement. In extremely high alkali content concrete, the use of fly ash and slag might not be sufficient to inhibit AAR expansion. If the concrete was not properly treated to inhibit AAR, the amount of expansion was increased with increasing the alkali concentration in the environment. The strategy of using fly ash and slag to inhibit AAR should consider the alkali content both in the concrete and in the environments.

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology): Vaal University of Technology
Strict environmental regulation on flue gas emission has led to the implementation of FGD technologies in power stations. Wet FGD technology is commonly used because it has high SO2 removal efficiency, high sorbent utilization and due to availability of the sorbent (limestone) used. SO2 is removed by passing flue gas through the absorber where it reacts with the slurry containing calcium ions which is obtained by dissolution. This study presents the findings of the dissolution of a calcium-based material (limestone) for wet FGD process. This was done using a pH stat apparatus and adipic acid as acid titrant. Adipic acid was used because of its buffering effect in wet FGD process. The conditions used for this study are similar to what is encountered in a wet FGD process. The extent of dissolution was determined by analyzing the amount of calcium ions in solution at different dissolution periods. The dissolution kinetics were correlated to the shrinking core model and it was found out that chemical reaction at the surface of the particle is the rate controlling step. This study also investigated the dissolution of coal fly ash and bottom ash. Their dissolution kinetics showed that the diffusion through the product layer was the rate controlling step due to an ash layer formed around the particle. The formation of ash layer was attributed to pozzolanic reaction products which is calcium-alumino-silicate (anorthite) compounds were formed after dissolution. The effect of fly ash on the dissolution of rate of limestone was also studied using response surface methodology. Limestone reactivity was found to increase with increase in the amount of fly ash added and the pH was found to be strong function of the rate constant compared to other dissolution variables. The presence of silica and alumina in fly ash led to a significant increase in the specific surface area due to hydration products formed after dissolution.
Eskom