The goal of the presented work was to find the most favorable conditions for the synthesis and stabilization of chemically pure ettringite and monosulfate. The reaction was carried out by mixing pure tricalcium aluminate (C₃A) and gypsum (C$\overline{\mathrm{S}}$H₂) in an excess amount of water. The impact of hydration time (2–7 days), C₃A:C$\overline{\mathrm{S}}$ molar ratio (1:1–1:3) and water vapor pressure of the selected drying agents (anhydrite-III and supersaturated CaCl₂ solution) on the phase composition of the products was evaluated. After 7 days of hydration, either ettringite or monosulfate was obtained as the main product, depending on the C₃A:C$\overline{\mathrm{S}}$ molar ratio. The synthesis carried out at a C₃A:C$\overline{\mathrm{S}}$ molar ratio of 1:3 produced pure ettringite. In the case of the sample characterized by the ratio of 1:1 (typical of monosulfate), a considerable portion of ettringite (27.9%) was present in the final products along the AFm phase. Therefore, a different synthesis method has to be selected in order to obtain pure monosulfate. The results showed that thermal analysis, X-ray diffractometry and FTIR spectroscopy can be used to distinguish the characteristic features of ettringite and monosulfate.

The influence of four naturally occurring mineral additives (zeolite, diatomite, trass and bentonite) on the hydration and properties of cement pastes and mortars was investigated. The materials change the phase composition, heat of hydration (determined by calorimetry) and mechanical properties of composites. After 28 days, the amount of Ca(OH)₂ was reduced by up to 23% and up to 35% more C-S-H was formed, as proved by TG measurements. Differences were observed in the kinetics of heat release, especially for 25% of the addition. In the calorimetric curves, an additional exothermic effect is observed, related to the alteration in the hydration of C₃A in cement. From the point of view of beneficial influence on mechanical properties of mortars, the additives could be ranked as follows: bentonite < diatomite, zeolite < trass after 2 days and bentonite < diatomite < trass < zeolite after 28 days of curing. The highest compressive strength (58.5 MPa) was observed for the sample with a 10% addition of zeolite. Zeolite, trass, bentonite and diatomite are all pozzolanic materials; however, their activity varies to an extent due to the differences in their specific surface area and the content of the amorphous phase, responsible for the pozzolanic reaction.

Lime quartz samples in which ground quartz sand was gradually substituted with waste glass powder (GP) were obtained under hydrothermal conditions to determine the influence of GP addition on the microstructure (observed by SEM), phase composition (analyzed by XRD), and compressive strength of autoclaved building materials. An additional series containing analytical grade NaOH and no GP was formed to evaluate the effect of sodium ions on tobermorite formation and its impact on the mechanical properties of the samples. GP addition hindered the formation of tobermorite during autoclaving. Instead, a higher amount of an amorphous and semi-crystalline C–S–H phase formed, leading to the densification of the composite matrix. Nevertheless, tobermorite-like structures were found during both XRD and SEM analyses, proving that the presence of small amounts of Al³⁺ ions allowed, to an extent, for the stabilization of the phase despite the high sodium content. The compressive strength values indicate that the presence of alkali in the system and the resulting formation of additional portions of C–S–H have a beneficial influence on the mechanical properties of autoclaved composites. However, the effect fades with increasing glass powder content which, together with a slight expansion of the samples, suggests that at high sand substitution levels, an alkali–silica reaction takes place.

In this study, ground granulated blast furnace slag was activated with a wide variety of sodium salts to compare the effects of their pH and anion size on the hydration progress and compressive strength development of GGBFS pastes. Research was carried out on samples activated with twelve different sodium salts and cured for one year. Changes in their phase composition (XRD), loss on ignition at different temperatures, expansion and microstructure (SEM + EDS) were examined over the entire curing period. The results showed that the presence of sodium ions is more important than the pH of the system, as activation took place even in the case of compounds whose solutions are characterized by a low pH, such as sodium tartrate or phosphate. The compressive strength of the pastes ranged from approximately 8 to 65 MPa after one year of curing.

In the study, ground granulated blast furnace slag was activated with a wide variety of sodium salts to compare the effect of their pH and anion size on the hydration progress and compressive strength development of GGBFS pastes. Research was carried out on samples activated with twelve different sodium salts, cured for one year. Changes in their phase composition (XRD), loss on ignition at different temperatures, expansion and microstructure (SEM+EDS) were examined over the entire curing period. Studies have shown that the presence of sodium ions is more important than the pH of the system, as activation took place even in the case of compounds whose solutions are characterized by low pH, such as sodium tartrate or phosphate. The compressive strength of the pastes ranged from approximately 8 to 65 MPa after one year of curing.