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Fly ash and a mixture of alkaline activators namely sodium silicate (Waterglass) and sodium hydroxide (NaOH) solution were used for preparing geopolymer. The aim of this research is to determine the optimum value of the alkaline activator/fly ash ratio. The effect of the oxide molar ratios of SiO2/Al2O3, water content of the alkaline activator and the Waterglass% content were studied for each Alkaline activator/fly ash ratio. The geopolymers were synthesized by the activation of fly ash with alkaline solution at three different alkaline activator/fly ash ratios which were 0.3, 0.35, and 0.4 at a specific constant ratio of waterglass/NaOH solution of 1.00. The geopolymers were cured at 70°C for 24 h and cured to room temperature. Results revealed that the alkaline activator/fly ash ratio of 0.4 has the optimum amount of alkaline liquid, which shows the highest rate of geopolymerization compared to other ratios. A high strength of 8.61 MPa was achieved with 0.4 of activator/fly ash ratio and 14% of waterglass content.

This paper represents the mechanical and microstructure changes in geopolymeric material synthesized by the alkali activation of locally source fly ash at high temperatures of 400, 600 and 800 °C. The high compressive strength of geopolymer cured at 70 °C underwent thermal shrinkage and substantial strength losing at temperatures of 400, 600 °C caused by the high dehydration of the structural water. Exposure to temperature of 800 °C, the geopolymer lost its strength due to extremely densification and expansion processes of the high unreacted silicate phase in the structure. The SEM results showed that the high activator content generated large quantities of unreacted silicate crystals at high temperatures which sintered at range of temperatures of 700-800 °C causing system failure.

In this study, the dependence of gamma-ray absorption coefficient on the particulate matter sizes of steel slag, iron fillings and steel balls incorporated concrete were examined. The contents of these fillers in concrete mix was kept constant to 35 wt. %. Only the filler particle size was varied during the tests. The particle size ranged from 0.2mm to 1mm for steel slags and the iron fillings and from 2.5mm to 10mm for the steel balls.The concrete samples were assessed for their anti-radiation attenuation coefficient properties. The attenuation measurements were performed using gamma spectrometer of NaI (Tl) detector. The utilized radiation source was Cs137 radioactive element with photon energy of o.662 MeV. The results showed that gamma-ray attenuation coefficient was inversely proportional to the filler particulate matter size. Likewise the mean free paths for the tested samples were obtained. Maximum linear attenuation coefficient of 1.102±0.263cm-1 was attained for the iron filling.The iron balls and the steel slags showed much inferior values. The concrete incorporates iron filings afforded the best shielding effect. The density, microstructure, homogeneity and particulate distribution of the concrete samples were examined and evaluated using different metallographic, microscopic and measurement facilities.

This paper reports the fire resistance property of a lightweight aggregate geopolymer concrete (LWAGC) material synthesized by the alkali-activation of locally source fly ash (FA) after exposed to elevated temperatures ranged of 100 °C to 800 °C. The results illustrates that the concrete gained a compressive strength after exposing to elevated temperatures of 100, 200 and 300 °C. Afterward, the strength of the LWAGC is started to deteriorate after exposing to elevated temperatures ranged of 400 °C to 800 °C, due to the difference in thermal expansion between the geopolymeric paste and LWA as well as to the evaporation of the structural water which increased the thermal shrinkage.