This study investigated the high temperature resistance of alkali activated slag based cements. Different liquids-to-solids (L/S) and Na₂SiO₃/NaOH proportions have been used in mix proportions in addition. Ordinary Portland cement (OPC) was used by replacing it with Ferrochrome slag (FS) at different percentages from 0 to 30. As alkaline liquid, sodium hydroxide and sodium silicate were used. Various L/S ratios (1/3, 2/3 and 1) and Na₂SiO₃/NaOH solution proportions (2.0, 2.5 and 3.0) were used in the preparation of samples. The highest compressive strength obtained in the blends that liquid/solid ratio was 1/3 and the Na₂SiO₃/NaOH ratio was 3. The samples produced at this specified ratios were exposed to temperatures between 100 °C and 800 °C. Beyond 400 °C, the compressive strength of alkali activated cement specimens in elevated temperature increased compared to the compressive strength of samples unexposed to elevated temperature. Increases in alkali activated cement at 800 °C were 41.1%, 28.5%, 43.9% and 46.64%, respectively, for S0, S5, S10 and S15 specimens.

The main purpose of this study was to investigate the compressive strength and microstructure characteristic of alkali-activated metakaolin cement (AAMC). In accordance with this purpose, besides the pure metakaolin activation five other mixtures were designed by substitution of different OPC ratios instead of metakaolin (MK) from 0 to 25 (5, 10, 15, 20, 25% OPC). AAMC was activated with sodium silicate (Na2SiO3) of modulus Ms = SiO₂/Na2O = 3.1 and NaOH solutions (32% of NaOH, 68% of water by mass). The ratio of liquid/solid (L/S) was kept constant at 0.65. All specimens were cured at 70 °C for 72 hours then kept in room conditions until the days that experiments were performed. Compressive strength and UPV experiment tests were carried out on all specimens at different curing periods of 3,14,28 and 90 days. In addition, the microstructure of 28 days alkali-activated metakaolin cements were analyzed with scanning electron microscope (SEM). The results showed that AAMC specimens reached the desired strength and major part of the final strength was gained at the end of 3 days of curing.

Considering global trends in sustainable and green development as well as the major drawbacks of conventional hydraulic cement, accelerate attempt for finding a suitable alternative and likely cause further development of geopolymeric cements in future. Influences of Nano scale Materials in improving the mechanical properties of ordinary Portland cement have been obviously proved. Despite the widespread use of these materials in different fields of science, for instance, chemicals engineering, materials engineering and even ordinary Portland cement, the effect of Nano scale materials in geopolymers has not been investigated deservedly. The purpose of this study is creating bridges to mitigate these gaps and shortcomings. Very fine silica particles (micro and Nano-silica) effects in ferrochrome slag based geopolymer have been evaluated in this research. Elazığ ferrochrome slag was used as the main aluminosilicate source and then it was blended with Nano silica or silica fume in little amounts in order to accelerate geopolymerization. Nano-silica and silica fume have been used at 2,4,6,8 and 10% of total binder weight in this study due to probe fine silica effect on the mechanical specification of produced material such as compressive strength, Static modulus of elasticity, Tensile Strength and microstructural change. The experimental results show all of these mention mechanical properties have been improved with adding fine silica in geopolymer mixes in optimum percentage of total binder weight. The best percentage of fine silica partial replacement instead of FS is 6% at all of silica fume and three Nano particle size (15, 30 and 45 nm). SEM images assessment demonstrated homogenous and denser texture with acceptable chemical bonds improvements for samples with optimum Nano-silica dosage. Compressive strength increase can be explained by densification of the matrix texture by using of Nano-silica and silica fume at optimum dosage.