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A new reinforced concrete foundation system is being proposed to store renewable energy through the compressed air energy storage technology. For this application, the concrete is required to resist considerable tensile strength and to have low air permeability, which is not observed in normal concrete. Therefore, this paper is proposing to use reactive powder concrete for the suggested foundation system. Reactive powder concrete (RPC) is obtained by introducing either micro-cementitious materials like silica fume or fine powders like crushed quartz into the concrete mixture from where coarse aggregates had been removed. RPC has low water content and dense particle packing which lead to high strength and low air permeability characteristics. This paper conducts preliminary experimental investigations on the strength and air permeability of the RPC. Two important mix design parameters are studied including water-to-binder ratio ad silica fume content. Preliminary correlations between mix design parameters and strength/air permeability are developed. From the preliminary test results, it is concluded that the reactive powder concrete has potential to meet the high strength and low air permeability requirements, and is suitable for the proposed energy storage foundation system.

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Strain hardening fiber reinforced geopolymer matrix, termed here as strain hardening material, is being proposed as a new seismic retrofitting material. Seismic behavior of the masonry walls with and without the strain hardening material was evaluated through finite element simulations in this paper. The finite element simulation was conducted on a masonry wall model with smeared crack material properties. The effectiveness of the strain hardening material for enhancing the seismic capacity of the masonry wall was evaluated through pushover analyses. Several parameters are considered in the pushover analysis including thickness and mechanical properties of the strain hardening material, wall geometries and loading directions. The force-displacement response obtained from the pushover analysis was used to develop a simplified multi-degree spring model. Nonlinear dynamic time history analyses were conducted using the spring model to evaluate the seismic demand of masonry structures strengthened with the strain hardening material. From the simulation results, it has been found that the strain hardening material can significantly improve the strength and ductility of the masonry wall under earthquakes. Design recommendations are made for retrofitting masonry structures using the proposed strain hardening material.