The thesis is focused on research and development of hydraulic binders based on FBC-ashes. It examines the possibilities of using this ash in the clinker so that the properties of the final cement are comparable to Portland cement. As an integral part of this thesis the research of emission reduction possibilities in the cement industry - a very current topic these days - is presented.

This diploma thesis is focused on long term monitoring of thermodynamic stability of ettringite under selected conditions and its possible destabilization or transformation into another AFt phase, especially thaumasite. Ettringite samples were made in two ways, by hydrating the yeelimite in the system with the alite and by addition of aluminium sulphate and calcium hydroxide.

This master’s thesis is focused on the effect of mixing water pH value on hydration and mechanical properties of cement composites based on portland cement. Source material was CEM I 42,5 R. Hydration process was analyzed by isoperibolic calorimetry, X-ray diffraction analysis and differential thermal analysis. Compressive and flexural strength was examined as mechanical properties. The samples microstructure was observed by scanning electron microscopy. Influence of mixing water pH value on flexural and compressive strength, retardation of hydration and ratio of individual phases was shown.

Diploma thesis discusses about design composition and firing process modification of belite clinker. It also deals with the summary of knowledge about chemistry and production technology of portland cements with respect to its ecology and economy.

The thesis is oriented on monitoring of hydration process of portland cement based on fluidized bed ash, firstly on investigation of AFt phases, mainly ettringite and thaumasite. Specific aim of the task is to prepare the scheme of these minerals synthetic preparation and to verify their laboratory preparation by different ways, using methods of RTG-diffraction analysis and scanning electron microscopy.

Heavy-metal contamination in soils has become a serious environmental problem. Among all metals, excessive amount of zinc was released to soils over the years. Zinc is not only toxic to human being, but also to plants. High concentration of zinc is extremely phytotoxic. Currently, the most popular method to remediate heavy-metal contaminated soils is stabilization/solidification (S/S) technique as it is cheaper, faster and more effective to remediate heavy metals than other remediation methods. Portland cement is the most-used binder in S/S technique. However, the production of Portland cement has released a significant amount of carbon dioxide, which strongly contributes to global warming. In addition, zinc retards the setting and hydration of Portland cement, which would require more Portland cement to remediate zinc-contaminated sites. Therefore, researchers are looking for new materials to improve the performance of Portland cement in zinc-contaminated soils. In recent years, the application of graphene-based materials in concrete had proved to be effective. Due to relative cost-effectiveness and comparable properties, multi-layer graphene, known as graphene nanoplatelets, may show a promising potential in construction. Moreover, research has reported that graphene nanoplatelets can be exfoliated from graphite and potentially scaled up for full-scale applications. At present, there is no application of graphene nanoplatelets in the S/S of contaminated soils and the roles of graphene nanoplatelets in cement-stabilized zinc-contaminated clay remained unknown. In this research, graphene nanoplatelets were dispersed in solution with a high-shear mixing apparatus. Dispersed graphene nanoplatelets solution was then applied to zinc-contaminated soil along with cement. To evaluate the efficacy of this S/S method, various influencing factors such as mixing sequence, graphene nanoplatelets content, zinc content, cement content, and curing time were studied. An optimum graphene nanoplatelets content was determined through the unconfined compressive strength (UCS) of the stabilized/solidified samples. It was found that at the optimum content, the unconfined compressive strength of cement-stabilized zinc-contaminated clay was improved by 22.3% with the addition of graphene nanoplatelets. Also, graphene nanoplatelets were effective at moderate zinc content and low cement content. Graphene nanoplatelets accelerated cement hydration effectively at early ages. Microstructural analyses indicated that more hydration products were developed in samples with graphene nanoplatelets. At current stage, it is still expensive to apply graphene nanoplatelets in S/S technique; however, it is possible to exfoliate graphite into graphene nanoplatelets in future research. / Graduate / 2022-05-12

The purpose of this research was to investigate the effects of reclaimed asphalt pavement (RAP) content and cement content on the strength and durability of recycled aggregate base materials. Specifically, the unconfined compressive strength (UCS) and final dielectric value in the Tube Suction Test (TST) were measured in a full-factorial experimental design including five RAP contents, five cement contents, and three replicate specimens of each possible treatment. Specimen mixtures consisted of 0, 25, 50, 75, or 100 percent RAP and 0.0, 0.5, 1.0, 1.5, or 2.0 percent Type I/II Portland cement. Both the RAP and base materials were sampled from the I-84 pavement reconstruction project performed in Weber Canyon near Morgan, Utah, during the summers of 2004 and 2005. The laboratory testing procedures consisted of material characterizations, specimen preparation, and subjection of the specimens to strength and durability testing, and the data were evaluated using analysis of variance (ANOVA) testing. Both the RAP and base materials included in this research were determined to be non-plastic, and the AASHTO and Unified soil classifications for the RAP material were determined to be A-1-a and SM (well-graded sand with gravel), respectively, and for the base material they were A-1-a and SW-SM (well-graded sand with silt and gravel), respectively. The optimum moisture contents (OMCs) for the blended materials were between 5.6 and 6.6 percent, and maximum dry density (MDD) values were between 129.7 and 135.5 lb/ft3. In both cases, decreasing values were associated with increasing RAP contents. The results of the ANOVA performed on the UCS data indicate that UCS decreases from 425 to 208 psi as RAP content increases from 0 to 100 percent and increases from 63 to 564 psi as cement content increases from 0.0 to 2.0 percent. Similarly, the final dielectric value decreases from 14.9 to 6.1 as RAP content increases from 0 to 100 percent and decreases from 14.0 to 5.8 as cement content increases from 0.0 to 2.0 percent. With design criteria requiring 7-day UCS values between 300 and 400 psi and final dielectric values less than 10 in the TST, the results of this research suggest that milling plans should be utilized to achieve RAP contents in the range of 50 to 75 percent, and a cement content of 1.0 percent should be specified for this material. Cement contents less than 1.0 percent are not sufficient to stabilize the material, and greater cement contents may cause cracking. Because control of the actual cement content in the field depends on the contractor's equipment and skill, inspection protocols should be implemented during construction to ensure high-quality work. Additional recommendations are associated with the construction process. The specimens prepared in this research were compacted to relative densities of 100 percent using modified Proctor energy. Therefore, field compaction levels must approach these density values if the same material properties are to be achieved. In addition, all specimens tested in this study were cured at 100 percent relative humidity. Following compaction in the field, cement-treated layers should be moistened frequently during the first few days after construction or promptly sealed with a prime coat or wearing surface to ensure that the cement continues to hydrate. Variability in RAP and cement contents should also be minimized to achieve consistent material properties.

This dissertation delves into the exploration of calcium carbonate polymorphs and silica-based materials upcycled from waste cement paste using a two-step extraction and carbonation process as supplementary cementitious materials (SCMs) to simultaneously achieve solid waste upcycling and carbon sequestration in the built environment. With the growing urgency to mitigate carbon emissions associated with the cement industry—one of the largest industrial contributors to anthropogenic CO₂ emissions globally—there is a pressing need to develop low-carbon alternatives that do not compromise the performance of concrete. This research is motivated by the potential of marrying carbon capture, utilization, and storage (CCUS) and alternative SCMs through CO₂ mineralization of industrial by-products and waste materials to lower the embodied carbon of cement and concrete. This approach addresses two critical issues: the reduction of construction and demolition (C&D) waste and the creation of highly reactive SCMs that can partially replace ordinary Portland cement (OPC). The dissertation is structured into two primary parts: the first focuses on the synthesis and potential applications of calcium carbonate polymorphs that can be derived from CO₂ utilization, and the second on the upcycling of waste cement paste into reactive silica-based materials. The first part (Chapters 2, 3, and 4) of the dissertation centers on three anhydrous calcium carbonate polymorphs, calcite, aragonite, and vaterite, which were synthesized under controlled laboratory conditions. These polymorphs were first characterized comprehensively using analytical techniques including scanning electron microscopy (SEM) to observe their distinct morphologies, X-ray diffraction (XRD) to determine their crystalline structures, laser diffraction (LD) to analyze their particle size distribution, and Brunauer-Emmett-Teller (BET) analysis to measure their specific surface areas. The rheology, hydration, and stability of these polymorphs were then investigated after they were used as substitutes for Portland cement (OPC) in cement pastes at 10 wt% or 20% replacement level. In Chapter 2, detailed rheological analyses were conducted, including rotational and oscillatory shear tests, to evaluate the influence of these polymorphs on the viscosity, yield stress, and structural buildup of cement pastes. Aragonite, with its needle-like crystals, was found to significantly enhance the static yield stress and structural build-up rates while having a minimal impact on dynamic yield stress, making it particularly suitable for applications requiring high thixotropy, such as 3D printing of concrete. In Chapter 3, the polymorphs were found to affect the hydration kinetics of the cement pastes, with aragonite exhibiting the most pronounced accelerating effect, thereby contributing to faster early-age strength development. The differences in thermodynamic stability of the three polymorphs also resulted in slightly different phase assemblages as revealed via thermodynamic modeling, indicating potential beneficial effects of using metastable aragonite and vaterite in cement-based materials. The metastable vaterite was also found to be stabilized in cement systems despite its instability and tendency to convert to calcite in aqueous environments. In Chapter 4, the mechanisms underlying the stabilization of vaterite in cement paste were explored with carefully designed experiments to construct model systems to decompose the complex cement-based systems and isolate dominating factors. The deposit and growth of cement-hydrated phases on the surface of vaterite and calcite seeds were found to be the dominant mechanisms preventing the transformation of vaterite to calcite, stabilizing metastable vaterite even in the presence of calcite seeding. The second part (Chapter 5) of the dissertation investigates the reactivity of amorphous silica-based materials extracted from waste cement paste using a pH swing process as alternative SCMs. The upcycling process involves the leaching of calcium from waste cement paste, followed by a pH swing to precipitate undesired elements to isolate calcium for CO₂ mineralization. The resulting materials, referred to as "residue" and "precipitate," were thoroughly characterized and found to exhibit strong pozzolanic reactivity. When used as 10% replacements for OPC, these upcycled materials significantly improved the compressive strength of cement pastes, particularly at early ages. The study also explored the phase assemblages formed in these cement pastes after hydration via XRD and the chemical circularity of silicate structures during the upcycling and reincorporation processes. The results indicated that the incorporation of these upcycled SCMs can contribute to the hydration of cement pastes and enhance their mechanical properties, which proved the feasibility of using these upcycled materials as alternative SCMs. Overall, this dissertation presents a comprehensive study on the potential of calcium carbonate polymorphs and upcycled silica-based materials as alternative SCMs to lower the embodied carbon of cement-based materials. Calcium carbonate polymorphs can be incorporated into cementitious materials to improve their rheological properties, hydration behavior, and mechanical performance, while amorphous silica-based materials exhibited high pozzolanic reactivity and contributed to the enhancement of compressive strength. This research paves a new way to decarbonize the built environment through the combination of solid waste upcycling and carbon sequestration, contributing to the global efforts to reduce the carbon footprint of the cement industry and promote a circular economy within the construction sector.

Portland cement concrete, the most widely used manufactured material in the world, is made primarily from water, mineral aggregates, and portland cement. The production of portland cement is energy intensive, accounting for 2% of primary energy consumption and 5% of industrial energy consumption globally. Moreover, Portland cement manufacturing contributes significantly to greenhouse gases and accounts for 5% of the global CO2 emissions resulting from human activity. The primary objective of this research was to explore methods of reducing the environmental impact of cement production while maintaining or improving current performance standards. Two approaches were taken, 1.) incorporation of waste materials in portland cement synthesis, and 2.) optimization of an alternative environmental friendly binder, calcium sulfoaluminate-belite cement. These approaches can lead to less energy consumption, less emission of CO2, and more reuse of industrial waste materials for cement manufacturing. In the portland cement part of the research, portland cement clinkers conforming to the compositional specifications in ASTM C 150 for Type I cement were successfully synthesized from reagent-grade chemicals with 0% to 40% fly ash and 0% to 60% slag incorporation (with 10% intervals), 72.5% limestone with 27.5% fly ash, and 65% limestone with 35% slag. The synthesized portland cements had similar early-age hydration behavior to commercial portland cement. However, waste materials significantly affected cement phase formation. The C3S–C2S ratio decreased with increasing amounts of waste materials incorporated. These differences could have implications on proportioning of raw materials for cement production when using waste materials. In the calcium sulfoaluminate-belite cement part of the research, three calcium sulfoaluminate-belite cement clinkers with a range of phase compositions were successfully synthesized from reagent-grade chemicals. The synthesized calcium sulfoaluminate-belite cement that contained medium C4A3 S and C2S contents showed good dimensional stability, sulfate resistance, and compressive strength development and was considered the optimum phase composition for calcium sulfoaluminate-belite cement in terms of comparable performance characteristics to portland cement. Furthermore, two calcium sulfoaluminate-belite cement clinkers were successfully synthesized from natural and waste materials such as limestone, bauxite, flue gas desulfurization sludge, Class C fly ash, and fluidized bed ash proportioned to the optimum calcium sulfoaluminate-belite cement synthesized from reagent-grade chemicals. Waste materials composed 30% and 41% of the raw ingredients. The two calcium sulfoaluminate-belite cements synthesized from natural and waste materials showed good dimensional stability, sulfate resistance, and compressive strength development, comparable to commercial portland cement. / text

For repairing concrete transportation infrastructure, such as pavements and bridges, much importance is placed on early-age strength gain as this has a major impact on scheduling and opening to traffic. However, the long-term performance and durability of such repair materials are often not satisfactory, thus resulting in future repairs. This research project focuses on the evaluation of the durability of various rapid-setting cementitious materials. The binders studied in this project include calcium aluminate cement (CAC), calcium sulfoaluminate cement (CSA), Type III portland cement, alkali-activated fly ash (AAFA) , and various prepackaged concrete materials. In addition, selected CAC and CSA mixtures were further modified with the use of a styrene-butadiene latex. The durability aspects studied include freezing-and-thawing damage and the implications of air entrainment in these systems, alkali-silica reaction, sulfate attack, and permeability of the concrete matrix and potential corrosion. / text