The use of supplementary cementitious materials (SCMs) in commercial construction have been increasing over the last several decades as climate change and sustainability has been gaining global attention. Incorporation of SCMs into concrete mixtures provides several environmental benefits. Since most SCMs are waste by-products of other industries, their use in concrete reduces waste disposal. Additionally, cements substitution with SCMs reduces the carbon footprint of the construction industry. Cement production generates large amounts of CO2 emissions; the use of SCMs reduces the amount of cement in a concrete mixture thereby reducing emissions from its production. In addition to SCMs, modern concretes typically incorporate a combination of chemical admixtures. Adverse interaction of admixtures with cement, with or without the SCMs, or with each other is one of the most common reasons for early-age concrete issues. Since the possible combinations of admixtures are numerous and there is a variety of cements on the market, testing all possible chemical/mineral/cement admixture combinations is impractical. The aim of this research was to cover a broad base of admixture-related issues, each addressing a specific need of the construction industry. There is currently no explanation for why calcium chloride-based accelerator is not always effective when used with high tricalcium aluminate (C3A) cements. It was determined that increasing C3A or gypsum content alone did not appear to significantly affect acceleration; however, the presence of alkalis reduced the effectiveness of CaCl2 accelerator. When CaCl2-based accelerators are used in concrete, they are typically used in combination with other chemical admixtures, such as water-reducing and retarding admixtures (WRRA) to allow for the use of a low water-cementitious material ratio. In order to avoid premature hardening, CaCl2 accelerator is most often added onsite, rather than at the concrete batching plant. Onsite addition can lead to accidental overdose of accelerator. It was found that increasing dosages of calcium chloride-containing accelerating admixtures in the presence of WRRA has a non-linear effect on the pore size distribution and consequently a non-linear increase on the autogenous shrinkage, which can contribute to early-age concrete cracking. Water-reducing admixtures and superplasticizers are added to concrete to improve workability, which decreases not only with a decrease in water-cementitious material ratio, but also with addition of some SCMs. Silica fume and metakaolin are known to decrease workability; fly ash and slag addition improve it. The effect of SCM combinations on workability is typically assumed to be additive. However, this investigation revealed that combining SCMs does not have an additive effect on workability, measured in terms of apparent yield stress and plastic viscosity; consequently, these parameters cannot be estimated from their respective values. Cement replacement with SCMs affects not only workability, but also heat of hydration, and is commonly used to reduce concrete temperature rise in concrete. Prediction and control of concrete temperature rise due to cement hydration is of great significance for mass concrete structures since large temperature gradients between the surface and the core of the structure can lead to cracking thus reducing durability of the structure. A number of equations have been proposed to predict the heat of hydration of cement and cement/SCM blends. However, these equations do not include metakaolin, which is a relatively new mineral admixture. Based on statistical experimental design, an equation was developed to predict the reduction of total hydration heat at 24, 48 and 72 hours with addition of SCMs compared to a plain ordinary portland cement (OPC)-water mixture. The developed equation allows the evaluation of the contribution of Class F fly ash (FA), blast furnace slag (BFS), silica fume (SF) and metakaolin (MK) as well as their combinations. Since metakaolin has been on the market for only about 10 years, the current knowledge on its effect on hydration products and paste microstructure remains incomplete. The effect of MK on the nature of hydration products was evaluated through x-ray diffraction. Its effect on the microstructure was assessed by measuring porosity with nitrogen adsorption and determining nanoindentation modulus as well as the volume fraction of calcium silicate hydrates (C-S-H) with variable packing densities. No significant effect was observed on the nature of hydration products with MK or BFS addition. However, nitrogen-accessible porosity increased with MK and BFS addition, the increase being larger with BFS. The average indentation modulus for the hydration products decreased with addition of MK and BFS, which corresponded to increasing nitrogen accessible pores. The results of this study indicate that phase quantification by quantitative x-ray diffraction (QXRD) of the hydrated paste may not be sufficient to assess the impact of metakaolin or BFS addition on the hydrating cementitious systems, and a multi-technique approach that provides information not only on the amount of hydration products, but also their morphology is preferable.

L'utilisation du kaolin calciné, sous forme de métakaolin, comme matériau pouzzolanique pour le mortier et le béton a suscité une attention considérable ces dernières années. Le travail actuel décrit les résultats d'un projet de recherche lancé pour étudier la calcination d'un kaolin local sous diverses températures (650-950°C) et durées (2, 3 et 4 heures) qui ont produit le métakaolin avec une activité pouzzolanique élevée. L'activité pouzzolanique a été évaluée par des méthodes de la chaleur d'hydratation et la résistance à la compression à 28 jours. L'activité maximale a été obtenue à une température de 850°C pendant 3 heures. Les résultats observés établissent qu'une augmentation de la chaleur d'hydratation et de la résistance à la compression a été obtenue lorsque le ciment Portland Ordinaire a été remplacé par 10% de métakaolin. L'utilisation du ciment ternaire améliore la résistance au jeune âge et à long terme. La durabilité a été également améliorée où une meilleure résistance des mortiers à l'attaque des acides a été observée. / The utilisation of calcined clay, in the form of metakaolin as a pozzolanic material for mortar and concrete has received considerable attention in recent years. The present work describes the results of a research project initiated to study the calcination of a local kaolin at various temperatures (650-950°C) and durations (2, 3 and 4 hours) to produced a metakaolin with a high pozzolanic activity. The pozzolanic activity was assessed by 28-days compressive strength and hydration heat methods. The maximum identified activity was obtained at 850°C for 3 hours duration. The observed results establish that an increase of both hydration heat and compressive strength was obtained when ordinary Portland cement was replaced by 10% metakaolin. The use of ternary blended cement improves the early age and the long-term compressive strength. The durability was also enhanced as better acidic resistance was observed.

Portland cement hydration is an exothermic process. The heat evolved during the hydration process is especially important in mass concrete, and hot and cold weather concreting. Heat of hydration is affected by several factors like chemical composition of cement, fineness of cement and ambient temperature. The major aim of this thesis is to investigate the effect of cement composition and fineness, amount and composition of the fine portion (&lt / 45 &micro / m) of natural pozzolan-incorporated cement on hydration heat. For this purpose, a portland cement and pozzolan-incorporated blended cements containing different amounts of natural pozzolan (trass) were used. The heat of hydration was measured using isothermal calorimetry. The values of heat of hydration for mixtures with different finenesses containing different amounts of added pozzolan were determined. The results obtained were used to find a correlation between the fineness, composition of cement and heat of hydration. According to this study, pozzolan incorporation in small amounts accelerates hydration. A similar effect was obtained for higher pozzolan amounts. Finer cements react faster and result in higher amounts of early heat evolved compared to coarser cements. In addition, it was found that the sum of the heat of hydration values of fine and coarse portion of cements was less than the total heat of hydration of blended cements. Moreover, a satisfactory correlation could not be established between results of isothermal calorimetry, and adiabatic calorimetry, setting time, and strength.

Thesis (M.A.)--University of Toronto, 2007. / "PCA R&D Serial No. 3030." (cover)

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Great works of infrastructure such as hydroelectric plants require, in it building, large concrete volumes classified as mass concrete structures. These works of power generation are strategic and fundamental for the development of a nation. However, during construction and throughout its life they may have pathological manifestations that compromise its stability. One of the most common problems in this type of structure is cracking caused by heat generated due to the exothermic reaction of cement hydration. Therefore, we had to analyze the thermal behavior of concrete, concrete with similar consistency and resistance like the concrete utilized in construction dam, and analyze how the type of cement utilized and its contents affects these parameters. In addition, we studied the evolution of compressive strength and dynamic modulus of elasticity as the cement hydrates. Finally, we compared the thermal performance of concretes produced with the results obtained from a commercial software. To carry out the experiment, concrete blocks were produced of 1,5m with cements CP II E 32 RS and CP IV 32 with consumption 241,2 kg/m and 330,0 kg/m for thermal analysis, besides cylindrical specimens for the remaining analyzes. The results showed that the thermal behavior of concrete has a small dependence on the type of cement, however the cement content affects too much this behavior, and the cement CP IV 32 showed higher thermal variations. It was also observed that the development of compressive strength is strongly dependent on the cement content, but it has low dependency on the type of cement. Computer modeling presented satisfactory results when it was compared to results of the thermal evolution blocks. / As grandes obras de infraestrutura como as centrais hidroelÃtricas requerem na sua construÃÃo grandes volumes de concreto, sendo classificadas como estruturas de concreto massa. Essas obras de geraÃÃo de energia sÃo estratÃgicas e fundamentais para o desenvolvimento de uma naÃÃo. Entretanto, durante sua construÃÃo e ao longo de sua vida Ãtil estas podem apresentar manifestaÃÃes patolÃgicas que comprometem sua estabilidade. Um dos problemas mais comuns nesse tipo de estrutura à a fissuraÃÃo causada pela energia tÃrmica gerada devido à reaÃÃo exotÃrmica de hidrataÃÃo do cimento. Diante disso, buscou-se analisar como se dà o comportamento tÃrmico de concretos utilizados para a construÃÃo de corpo de barragem, alÃm de analisar como o tipo de cimento utilizado e o seu teor afetam a variaÃÃo de temperatura da massa de concreto e os problemas causados por essa variaÃÃo. Buscou-se ainda analisar a evoluÃÃo da resistÃncia à compressÃo e do mÃdulo de elasticidade dinÃmico à medida que o cimento se hidratava. Por fim, comparou-se o comportamento tÃrmico dos concretos produzidos com os resultados obtidos por meio de um software comercial. Para a realizaÃÃo da parte experimental produziu-se blocos de concretos de 1,5 metros cÃbicos com cimentos CP II-E 32 RS e CP IV 32 com consumo de 241,2 kg/m e 330,0 kg/m para anÃlise tÃrmica, alÃm da moldagem de corpos de prova cilÃndricos para as demais anÃlises. Os resultados apontaram que o comportamento tÃrmico do concreto apresenta uma pequena dependÃncia do tipo de cimento. Entretanto, o teor de cimento afeta fortemente esse comportamento, sendo o cimento CP IV 32 o que apresentou maiores variaÃÃes tÃrmicas. Observou-se tambÃm que a evoluÃÃo da resistÃncia à compressÃo à fortemente dependente da quantidade de cimento, mas apresenta baixa dependÃncia do tipo de cimento. A modelagem computacional apresentou resultados satisfatÃrios quando comparado aos resultados da evoluÃÃo tÃrmica dos blocos produzidos.

The theme of this diploma thesis is the design and assessment of a part of the underground load-bearing structure of the administrative center according to the source material. Emphasis is placed on the design, taking into account the waterproofness of the construction, the so-called white tank. This is ensured by the correct design of the concrete construction of the foundation slab and walls, taking into account the constructional details of the day and expansion joints, the concrete composition and the construction process.

Student Number : 9900772K - MSc research project - School of Civil and Environmental Engineering - Faculty of Engineering and the Built Environment / The hydration of cement is an exothermic reaction, which begins almost immediately upon contact with water. This produces a large amount heat that subsequently raises the temperature of the concrete mixture, creating a temperature gradient across the member. The temperature rise associated with hydration induces thermo-mechanical stresses. These stresses can cause damage to the structure, affecting the durability and in extreme cases the functionality of the structure. If the maximum rate of heat evolution experienced can be minimised through the selection of the constituents of a concrete mixture, then the thermal stresses that develop in the concrete can be reduced. The main aim of this research is to develop a knowledge of how the heat evolution characteristics of concrete are affected by changing certain concrete mixture parameters and ingredients. The focus is on the addition of three different cement extenders and varying the water/cement ratio. This will be a step towards the development of a model for predicting the thermal properties of concrete. As a part of this investigation, a prediction model for the change in heat rate in concrete was developed. The model is intended to predict the contribution of the individual clinker crystallographic phases in cement and the heat liberated in concrete during hydration.

Ce travail s’intéresse à la formulation et à la caractérisation de mortiers cimentaires imprimables en 3D. Il a été réalisé dans le cadre du projet MATRICE cofinancé par le fonds Feder et la région Hauts de France. Un cahier des charges pour un matériau cimentaire imprimable est tout d’abord défini sur la base de trois critères : l’extrudabilité, la constructibilité et la conservation des résistances mécaniques sur matériau imprimé. Deux mortiers imprimables sont formulés en utilisant des essais simples à l’échelle du laboratoire. Le premier mortier, à prise lente, est composé d’un liant à base de ciment Portland (OPC). Le second mortier, à prise accélérée, est composé d’un liant mixte (93 % d’OPC et 7 % de ciment sulfoalumineux (CSA)). Des impressions à l’échelle réelle sont ensuite réalisées dans le cadre du projet MATRICE et permettent de valider leur imprimabilité selon l’application de chacun. Le comportement chimique de mélanges de ciment Portland et de ciment sulfoalumineux est ensuite étudié expérimentalement. Les chaleurs d’hydratation mesurées par calorimétrie isotherme augmentent avec le dosage en CSA (de 2 % jusqu’à 10 %) et sont plus élevées que celles des pâtes de ciment contenant 100 % d’OPC et 100 % de CSA. La comparaison des hydrates identifiés dans le mélange à 7 % de CSA à ceux présents dans les deux pâtes de ciment pures montre que la présence de gypse et de chaux provenant du ciment Portland entraîne une hydratation plus rapide de la ye’elimite provenant du CSA et une formation d’ettringite à très court terme. Par contre, la nature des hydrates du ciment Portland n’est pas affectée. Le comportement rhéologique, notamment, la thixotropie, de pâtes constituées de mélanges de ciment Portland et sulfoalumineux (jusqu’à 10 %) est ensuite étudié en fonction de différents paramètres de formulation pendant la première heure. L’augmentation du dosage en CSA (0 % à 10 %) entraîne une augmentation quasi linéaire du coefficient de structuration (Athix) de ces mélanges. Pour les mélanges à 7 % de CSA et 100 % d’OPC, l’influence du rapport E/C et du dosage en superplastifiant sur la thixotropie est ensuite étudiée. L’augmentation du rapport E/C entraîne une diminution quasi linéaire de Athix pour chacune des pâtes de ciment. En revanche, le superplastifiant présente une faible influence comparativement au rapport E/C. / The interest of this study is the formulation and characterization of 3D printing cementitious mortars. This research work has been carried out in the frame of the MATRICE Project, co-funded by the region “Hauts de France” and the European Union with the European Regional Development Fund. Specifications for a cementitious printable material are first set based on three criteria: extrudability, buildability and conserving the compressive strength of the printed material. Two printable mortars are formulated using simple tests on a laboratory scale. The first, with slow setting, is composed of a Portland-based binder (OPC). The second, with accelerated setting, is composed of a mixed binder (93% OPC and 7% sulfoaluminous cement (CSA)). Real scale prints are then realized in the frame of the project MATRICE allowing the validation of the printability of each mortar upon its application. The chemical behavior of Portland cement and sulfoaluminate cement mixes is then studied experimentally. The heats of hydration measured by isothermal calorimetry increase with the CSA dosage (2% to 10%) and are higher than those of cement pastes containing 100% OPC and 100% CSA. The comparison of the hydrates identified in the mix mad of 7% CSA to those present in the two other cement pastes of each cement alone shows that the presence of gypsum and lime from the Portland cement lead to a faster hydration of the ye’elimite from CSA and to an early formation of ettringite. However, the nature of hydrates is not affected. The rheological behavior, in particular the thixotropy, of the cement pastes made of Portland cement and sulfoaluminate cement (up to 10%) is then studied in function of different formulation parameters during the first hour. The increase in CSA dosage (0% to 10%) leads to an almost linear increase of the structuration coefficient (Athix) of theses mixes. For mixes with 7% CSA and 100% OPC, the influence of the W/C ratio and superplasticizer on the thixotropy is then studied. The increase in W/C ratio leads to an almost linear decrease of the Athix for each of cement paste. However, the superplasticizer present a low influence compared to the W/C ratio.

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.

The determination and following up the development of properties during the fresh state and early ages of concrete are important in order to schedule the work and to obtain the desired properties in the hardened concrete. As the traditional methods such as Vicat and Penetrometer mostly depend on the experience of the operator and do not provide a continuous picture of the development of properties, reliable and objective non-destructive test methods are needed for the quality control of fresh concrete. The purpose of this thesis is to observe the development of properties of fresh pastes and mortars continuously by longitudinal ultrasonic waves. For this purpose, cement pastes and mortars with three different w/c ratios were prepared with ordinary portland cement. The ultrasonic pulse velocities were determined continuously during hydration. The setting times were also determined by standard test methods. The flexural and compressive strength were determined at 1, 2, 3, 7 and 28 days by standard test method and the volume of permeable pores were also obtained at the same ages. Lastly, the heat of hydration of cement pastes of similar w/c ratios were determined by isothermal calorimetry. UPV (Ultrasonic Pulse Velocity) development was compared with the results of standard tests applied on the samples. The results revealed that the UPV is a useful method in monitoring the hydration process of cementitious materials.