The feasibility of producing sustainable cement-free composites and its environmental impact were investigated in this research. Experimental parametric evaluation was carried out in this regard to explore the optimum mix design of the composites. The effect of synthesis parameters and curing conditions on the behavior of the produced geopolymer composites was investigated. The studied parameters included the molarity of the sodium hydroxide solution (12 M, 14 M, and 16 M), the sodium silicate to sodium hydroxide ratio (1, 1.5, 2, and 2.5), the fluid to binder ratio (0.6, 0.65, and 0.7), and the age. The curing conditions included ambient curing and heat treatment at 40 °C, 80 °C, and 120 °C for 24 h, 48 h, and 72 h. In addition, life cycle assessment was performed to compare the environmental impact of geopolymer and cementitious composites. The results reflected the possibility of producing geopolymer composites with significant positive environmental impacts over traditional cementitious composites. The synthesis parameters played a major role in the behavior of the produced geopolymers. Heat curing was necessary for the geopolymer mortar to achieve high early strength. However, strength development with age was more obvious for ambient-cured specimens than heat-cured specimens. The optimum fluid to binder ratio used in this research was 0.6. For this ratio, the compressive strength increased as the molarity of the sodium hydroxide solution increased for all sodium silicate to sodium hydroxide ratios. Finally, SEM images showed that the higher the molarity and as the amount of reacted FA particles increased, the better the microstructure of the geopolymer mortar was and the fewer pores the matrix had.

This paper investigates the performance of a new generation of nanoparticle-reinforced polymeric materials as an alternative to fiber-reinforced polymer for the protection of masonry structures against blast loads. The nanoparticles used in this study include exfoliated graphene nano platelets (XGnP) and polyhedral oligomeric silsesquioxane (POSS). The polymer is polyurea. A one-quarter scale physical model of unreinforced masonry walls, spray coated with the nanoparticle-reinforced polymers, are subjected to blast load in the Engineer Research and Development Center Blast Load Simulator facility. POSS-reinforced polyurea is observed to significantly enhance the performance of masonry walls sustaining blast loads, whereas XGnP reinforcement has only marginal improvement. To build a numerical simulation and engineering design capability, computer models using ANSYS AUTODYN and simplified analytical models are constructed. These models fairly accurately predict the observed laboratory tests.