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Accelerating and mineral admixtures, one of the major ingredients in concrete, are primarily used to modify the properties of both fresh and hardened concrete. Within the scope of this thesis, there were four types of cements having almost identical fineness. The mixes were prepared by using natural pozzolan, blast furnace slag and limestone conforming to TS EN 197-1 and two types of accelerating admixtures, namely triethanolamine (TEA) and calcium formate (CF). The effect of set accelerating admixtures with different cement types on the setting time, water demand and compressive strength has been analyzed by an experimental study in accordance with relevant ASTM standards. Finally, it has been observed that the amount of the accelerating admixtures used is suitable because of their effects on the water demand, setting and strength. Due to the density difference of mineral admixtures and clinker, the normal consistency and 110% flow water content should be considered on a volumetric basis. The effectiveness of the accelerating admixtures on the normal consistency water, 110% flow water content and setting time depends on the type and amount of mineral admixtures. The increase caused by CF in the normal consistency and 110% flow water content is higher than that by TEA. The accelerating effect of TEA and CF on the setting times is more significant for cements incorporating 6% mineral admixture. The effects of accelerating admixtures on the compressive strength change with specimen age, type and amount of mineral admixtures. Generally, for all cement types, early age compressive strengths increase with the increase of TEA, however long term strengths increase by increasing CF.

Mineral and chemical admixtures are used today in almost all concrete mixtures to improve concrete fresh and hardened properties, and to enhance concrete durability. In this study, four mineral and four chemical admixtures were investigated: namely, metakaolin (MK), silica fume (SF), Class F fly ash (FA), blast-furnace slag (BFS), two high-range water reducers (SP), water reducer/retarder (WRD), and air-entrainer (AEA). The objective of this study is to assess the effects of commonly used mineral and chemical admixtures on the durability of the cementitious system. Two durability issues were addressed in this study: the potential of the cementitious system to generate heat, and sulfate durability. The properties studied here included heat of hydration (HOH) measurements using isothermal calorimetry, setting properties, compressive strength, and expansion on exposure to a sodium sulfate solution. X-ray diffraction was used to characterize the as-received materials and explain failure trends. The findings of this study indicate that silica fume inclusion sustains superior durability in comparison to the other mineral admixtures considered here. Replacement levels as low as 10% outperformed the other admixtures studied. Fly ash showed improvement in the workability of the mixes, but had the lowest compressive strength results and might pose challenges when the rate of strength gain is critical. However, Class F fly ash mixtures showed better performance than unblended mixtures when exposed to a sulfate source. Metakaolin mixes showed higher heat evolution among all the mixtures studied here. This can potentially lead to durability concerns, especially when temperature rise is a design concern. Blast-furnace slag also improved the workability of the mixes and the later compressive strength, but had mixed performances when examined for sulfate durability.

The mining industry is a major economic driver and job creator for many countries. However, mining is associated with geo-hazards and environmental issues, such as the disposal of large volumes of waste, acid mine drainage, and ground subsidence. As a result, efficient mining waste management is crucial for sustainable development. The geotechnical, economic, and environmental benefits of cemented paste backfill (CPB) have piqued the interest of researchers and academicians worldwide, making it an essential aspect of underground mining management. CPB is a thickened cementitious combination of dewatered tailings (70 - 85 wt.%), binders (usually 3 to 8% wt.%), and water used to backfill mine waste into underground mining stopes. Despite being used in small amounts, the cost of cement makes up to 80% of the cost of backfilling operations. In addition, clinker production accounts for 5-8% of global human created carbon dioxide (CO₂) emissions. This predicament necessitates the development of a viable alternative to cement. Partially substituting cement with supplementary cementitious materials like fly ash, blast furnace slag, natural pozzolans, and other materials has been increasingly prevalent in CPB. It is evident that the addition of slag to cement can increase the mechanical strength of CPB at the advanced ages but decreases the strength and suction development due to the slow reaction kinetics in the CPB at the early ages, which may negatively affect the mechanical stability of the CPB, mining cycle, and safety of mineworkers. Moreover, the supply of these materials is limited and may not be enough for the future needs of the industry. Furthermore, there has been a surge in interest in using limestone powder (LS) owing to its abundance, low cost, and lack of environmental costs which are associated with Portland cement - Type 1 (PCI). The addition of LS accelerates hydration at the early ages, thus resulting in high early strength, but the dilution effect can reduce the late strength. The combination of LS and slag in a ternary blended cement can be potentially used as a binder for CPB with acceptable strength development at the early and advanced ages while lowering the cost of the CPB and the carbon footprint of the mining industry. Nevertheless, the rheology, mechanical strength, and stability are important key performance quality criteria for CPB; however, the effect of ternary cement blends on these parameters is not well known. In this research program, the impact of the binary and ternary cement blends on (i) the fresh properties of CPB, such as the rheological properties (yield stress, viscosity) and setting time, and (ii) the strength and suction development of CPB are investigated. To understand the effect of substituting slag with LS in the binary binder in the first phase of the study, binary binders with two differ-ent PCI: Slag proportions of 50/50 and 80/20 are examined with no limestone, followed by replacing slag with an increasing amount of LS from 0 to 20 wt. % of the total binder, with a constant cement content, over a period of 4 hrs (0, 0.25, 1, 2, and 4 hrs) of curing at room temperature. In the second phase, the effect of a ternary binder (PCI-Slag- LS) with varying proportions on the suction development and the mechanical behavior of hardened CPB is investigated over a curing period of up to 90 days. The changes in strength of these binary and ternary binders on the CPB sample are tested for 1, 3, 7, 28, 60, and 90 days. An unconfined compression test (UCS) is conducted to evaluate the strength development. The microstructure of the mixes is examined through mercury intrusion porosimetry (MIP) for changes are validated through monitoring for the development of hydration and suction, electrical conductivity (EC), and temperature, which is carried out for up to 30 days. This is followed by a microstructure analysis with a thermogravimetric/differential thermogravimetric test on fresh and hardened samples. The results of the first phase show that an increase in the percentage of substituted cement in the binary binder (from PCI/Slag 80/20 to 50/50) increases the yield stress of the CPB but decreases the viscosity of the mix. However, the addition of LS as a substitution for slag shows a considerable decrease in the yield stress of the control mix with an increase in viscosity with increasing dosages of LS, thus indicating an improvement in the flowability of CPB. The second phase results indicate that the slow hydration kinetics of slag influences early age suction and strength changes in the binary sample with a high slag content (50/50); however, its latent hydraulic and pozzolanic properties enhance strength gain after 28 days. The addition of 5% limestone to the ternary blend increases the strength gain by up to 7 days compared to the binary control samples. Indeed, the presence of LS influences the rate of hydration of cement and slag through both physical (filler, nucleation, dilution) and chemical (hydrate) effects. However, substituting more than 10% LS for slag affects the mechanical performance at all ages. Overall, up to 50 wt.% slag and 10 wt.% limestone with cement as a ternary binder can be used without significant compressive strength loss. This study demonstrates that the partial substitution of ordinary Portland cement (OPC) with varying percentages of slag and LS is complementary, and overall, the interaction of slag and LS is observed. The optimal use of LS and slag in a ternary system may serve as a sustainable alternative to the commonly used OPC and PCI/Slag binders, thereby reducing the energy consumption and carbon footprint associated with cement. The findings of this study will ultimately help to develop a better understanding of the impact of ternary blends with increasing percentages of LS on the rheology and setting time of CPB mixes and mechanical strength changes in designing an efficient mixing plant, particularly its transport system.

Cemented paste backfill (CPB) is a highly advantageous method of backfill that has been increasing in use in recent decades as it provides many environmental, economic, and practical benefits. When combined with cement and water, it recycles a portion of the dewatered tailings produced from mines as backfill for underground stopes. CPB is transported from the plant on the surface through pipes to the stopes, sometimes over several kilometers, and then placed in underground mining cavities (stopes) to support the ground or rock mass. Therefore, it must meet certain rheological, setting time, and strength gain performance requirements. Additionally, as many mines around the world are located in areas of freshwater scarcity, and societies are holding corporations to ever higher standards for humanitarian and environmental responsibility, many mines are seeking to utilize locally available, saline groundwater or seawater as mixing water in backfill. The impacts of this decision on the rheological, setting, and strength properties of CPB must be better understood to allow for the confident selection of this convenient solution, as the risks associated with improper design include huge costs due to pipeline clogging and death or injury due to backfill failure and ground subsidence. NaCl is a contributor to natural groundwater and seawater salinity and may be present in concentrations of up to 300 g/L. An additional cost-saving measure favoured by mines is to replace some of the costly Portland cement with much cheaper supplemental cementitious materials such as blast furnace slag. Therefore, this thesis examines the impacts of NaCl concentration and binder composition on the yield stress, viscosity, initial and final setting time, and strength development of CPB. A robust experimental program has been undertaken in which CPB was subjected to the above-mentioned tests in addition to pH and MIP testing, SEM, TG/DTG, XRD, and zeta potential analyses, and electrical conductivity, suction, and water content monitoring. CPB samples were made with synthetic silica tailings, Portland cement, and water with NaCl concentrations of 0 g/L, 10 g/L, 35 g/L, 100 g/L, and 300 g/L and CPB made with 35 g/L and slag replacement percentages of 0%, 25%, 50%, and 75%. Additional samples tested were made with natural gold tailings, Portland cement, and NaCl concentrations of 0 g/L and 35 g/L for verification. Rheological testing was conducted at 0 minutes, 15 minutes, 1 hour, and 2 hours after mixing, and UCS testing was conducted after 1 day, 3 days, 7 days, 28 days, and 60 days of curing. Additional tests or analyses were performed on selected mixes and curing times for optimum insight and monitoring was conducted from 0 to 28 days after curing. It was found that low concentrations of NaCl (10 g/L and 35 g/L) generally had favourable impacts on the UCS and setting times of CPB, while higher concentrations had negative impacts. The impacts of slag replacement on UCS development of saline CPB were also generally favourable. However, the impacts of slag replacement on initial setting time were generally negative, and favourable at higher replacements (50% or more) for final setting time. Low NaCl concentration led to slightly negative impacts on yield stress, especially at longer curing times (1-2 hours), but high concentrations greatly reduced the yield stress. NaCl concentration had minor impacts to viscosity, with any concentration leading to a slightly higher initial viscosity but slightly lower viscosity at longer curing times. Slag replacement content had negligible effects on yield stress, but led to favourable decreases in viscosity over longer curing times. The combination of positive and negative impacts indicates that care must be taken to knowledgeably prioritize or balance critical properties in mix design, though there is indication of opportunities for overall improvement. Supplemental testing provided useful information to explain the mechanics behind the results which will allow designers to carefully select the required components for the desired properties.

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.

This masters thesis deals with influence of cement bypass kiln dust on physico-mechanical properties of alkali activated slag and influence of chosen compounds of cement bypass kiln dust on alkali activated slag. Using alkali activated slag is limited by its shrinkage. The setting time with different amount of cement bypass kiln dust and its chosen compounds (CaO, KCl and K2SO4) were measured by isotermal and isoperibolic calorimetry too. The strength and length changes of the mixtures with different amount of cement bypass kiln dust were measured. Samples were analysed by X-Ray diffraction analysis and scanning electron microscopy. It has been found that the increasing addition of dust reduce setting time, flexural and compresive strength and shrinkage. Presence of free CaO was found being one of the reasons for accelerated setting. KCl and K2SO4 have retarding effect but influece of free CaO prevails even for its lower contents. Long-term properties evolution is strongly dependent on curing regime due to potential volume expansion.

Man vill förkorta betongs bindetid dvs. den tid då betongytan kan behandlas så att betongytan blir slät efter gjutning. Det är en stor utmaning för företag som tillverkar fabriksbetong vintertid, eftersom bindetiden förlängs ju kallare klimatet är. Syftet med denna labboration var att visa hur Kalciumnitrart fungerar som bindetidsaccelerator i betong, och om Kalciumnitrart påverkar betongens fysikaliska egenskaper.  Följande faktorer har studerats för att se hur dessa faktorer påverkar betongens bindetid i kombination med användning av Kalciumnitrat. Betongens utgångstemperartur Typ av flyttillsatsmedel i betongen Betongens utgångskonsistens Betongens lagringsklimat Även hitta rätt dosering för att denna produkt ska vara lönsamt att användas i praktiken. Alla underökningar har utförts hos Sika AB laboratorium. All data har noggrant undersökts och använts i Excel program för framtagning av tabeller och diagram. Resultaten/slutsats i underökningarna visade följande. Bindetiden kan förkortas med Kalciumnitrat utan att behöva riskera betongens fysikaliska egenskaper. Enligt bindetidsdiagram noterades att 2,0 % och 2,5 % doseringarna gav bästa resultat gällande bindetid dvs. de gav kortast bindetid. Observera att +5 graders lagringsklimat gav ologiska resultat dvs. referensbetongen utan acceleratorn gav kortast bindetid. Tryckhållfastheten påverkas inte av acceleratorn dvs. man kan använda denna produkt utan att riskera betongens bärförmåga. Resultaten visade att betongens utgångskonsistens har stor betydelse för bindetiden, ju högre konsistens värde desto längre bindetid. Även betongens utgångstemperatur har påverkan på bindetiden, ju högre betongtemperatur desto kortare bindetid. / You want to reduce the concrete’s initial setting i.e.  the time the concrete surface can be treated so that surface gets plane after molding. It’s a big challenge for the companies that produce mill concrete in winter. Since the colder the climate gets the binding process will be extended. The purpose of this lab was to show how Calcium Nitrate functions as bonding time accelerator in concrete and if Calcium Nitrate affects the physical features of the concrete. The following elements have been studied to see how these elements affect the initial setting of the concrete in combination with the use of Calcium Nitrate. The initial temperature of the concrete The type of super plasticizer in the concrete The initial consistency Concrete storage climate Even finding the right dose so that this product will be profitable to use in the practice. All investigations have been made at Sika AB laboratory. All the data have been investigated and used in excel program for the product of chart and diagram. The results of the investigations showed the following:   Bond time can be reduced with Calcium Nitrate without needing to risk the physical features of the concrete.  According to bonding time diagram it was noted that 2.0 % and 2.5% doses gave the best result valid the initial setting i.e. that gave the shortest time of initial setting, Observe that +5 degrees storage climate gave illogical results i.e. reference concrete without the accelerator gave the shortest initial setting. Compressive strength does not get affected by the accelerator i.e. you can use this product without risking the concretes carrying capacity.  The results showed that the concrete initial consistency has a big importance to bond time, the higher consistency value the longer time of initial setting. Even concrete initial temperature has influence on the bond time, the higher concrete temperature, the shorter time of initial setting.

Este estudo teve como objetivo avaliar os efeitos de variações no protocolo de ativação e envelhecimento acelerado em algumas propriedades de cimentos resinosos de polimerização dual. Adicionalmente, investigaram-se os efeitos da variação da temperatura ambiente e envelhecimento acelerado no tempo de trabalho e tempo de presa dos cimentos quando ativados exclusivamente pela reação química. As propriedades avaliadas foram o grau de conversão, determinado por espectrometria no infravermelho com transformada de Fourier (FTIR-ATR), microdureza Knoop, expressa em KHN, e resistência mecânica à tração expressa em MPa. Os tempos de trabalho e tempos de presa foram determinados por um reômetro oscilatório com controle de temperatura da plataforma de teste estabelecida em 24oC ou 37oC. O envelhecimento acelerado foi determinado pela armazenagem dos cimentos, em suas embalagens originais, e após os testes iniciais, em estufa a 37oC por 12 semanas.A variável de modo de ativação foi determinada em 3 níveis. Os cimentos foram manipulados de acordo com as instruções dos fabricantes e ativados por luz imediatamente (controle), ativados por luz após 10 minutos de reação química no escuro (Exp 1) ou mantidos no escuro por 15 minutos, permitindo a reação química, mas sem fotoativação (Exp 2). Os cimentos tiveram suas propriedades avaliadas em função desses diferentes modos de ativação, antes e após o envelhecimento acelerado. Cimento exclusivamente ativado pela reação química foi empregado como controle quando necessário. Os diversos resultados podem ser resumidos em alguns aspectos de interesse. O tempo de trabalho e o tempo de presa de todos cimentos foram afetados significantemente pela temperatura e envelhecimento (p<0.05). O aumento da temperatura acelerou os tempos de trabalho e presa. Os efeitos do envelhecimento foram materiaisdependentes. Alguns materiais apresentaram redução, enquanto outros apresentaram aumento dos tempos de trabalho e presa, independentemente da variação da temperatura. O modo de ativação e envelhecimento afetaram significantemente as propriedades dos cimentos (p<0.05). Em geral, o grau de conversão aumentou com o tempo após a fotoativação. O retardo da fotoativação por 10 minutos causou alterações no grau de conversão, independentemente do envelhecimento, e para alguns produtos somente. O envelhecimento afetou a cinética da reação química de polimerização dos cimentos. Alguns materiais não apresentaram suficiente reação química após o envelhecimento. As propriedades variaram amplamente de acordo com o modo de ativação e produto. O envelhecimento foi a variável que causou alterações mais significantes e com grande implicação na utilização clínica dos produtos. Alguns materiais se tornaram impróprios para uso após o envelhecimento acelerado. / The study aimed to evaluate the effects of curing protocol and accelerated aging on some properties of dual-cure resin cements. Additionally, the effects of different ambient temperature and aging on the working and setting times were investigated when cements were self-cured only. Properties evaluated were degree of conversion as determined by FTIR-ATR spectroscopy, Knoop microhadness as expressed by KHN, and tensile strength as expressed in MPa. Working time and setting time were determined by an oscilating rheometer with controlled temperature stage at either 24oC or 37oC. Accelerated aging was performed by storing the original product kits in an oven at 37oC for 12 weeks after initial testing had been executed. Different curing protocols were established in 3 levels. Cements were manipulated according to the manufacturers instructions and light-activated immediately (control), light-activated after 10 minutes delay of self-curing in the dark (Exp 1), or simply allowed to self-cure for 15 minutes in the dark (Exp 2). Properties were evaluated according to the different curing protocol and both before and after aging. Exclusively self-curing cement was used as control product when appropriate. The results can be summarized in some aspects of interest. The working time and setting time of all products were significantly affected by temperature and aging (p<0.05). Increased temperature resulted in shorter working time and setting time. The effects of aging were material dependent. Some products presented reduced working and setting times, while others behave otherwise, regardless of the temperature. Curing mode and aging significantly affected the properties of the cements (p<0.05). In general, the degree of conversion increased with time after light-activation. The curing delay for 10 minutes caused alterations in the degree of conversion, regardless of aging, for some products, but not all. Aging affected the curing kinectics and general properties of all cements. Some materials did not present sufficient cure after aging. Properties varied widely according to curing protocol and product. Aging was the variable that most affected the products and the most relevant regarding the clinical use of the materials. Some products were deemed improper for clinical use after accelerated aging.