Influence of Reinforcement Ratios on Load and Deflection of Reinforced Geopolymer Concrete Beams

Abstract

In recognition of the adverse environmental impacts of the Portland cement manufacturing process, interest has shifted toward developing alternative cementing materials. This shift is also driven by the depletion of fossil fuel reserves, scarcity of raw materials, and the increasing demand for cement and concrete. However, geopolymer cement can serve as a substitute for Portland cement binder in structural concrete. In this research, Reinforced concrete geopolymer concrete beams were produced with metakaolin as the pozzolan. The concrete was produced with a cement made up of metakaolin as the silica and alumina precursor, while Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3) serve as the activator solution. Singly reinforced concrete beams were produced at 1.24%, 1.96% and, 2.86% reinforcement ratios using 8, 10, and 12mm steel reinforcements respectively. The beams were tested according to BS EN 12390-5 (2000). The results showed that the dominant mode of failure of the beams is the diagonal tension shear failure. Additionally, the behavior of the reinforced geopolymer concrete (RGC) beams in deflection was found to be similar to conventional reinforced concrete (RC) beams. Furthermore, the load required for a deflection of 1mm when the reinforcement ratio is 1.24%, 1.96% and, 2.86% is respectively 14kN, 20kN, and 29kN. In addition, a load of 20kN lead to a deflection of 1.33mm, 1.00mm, and 0.65mm for reinforcement ratios of 1.24%, 1.96% and, 2.86% respectively. The maximum deflection at failure of the beam with a 1.24% reinforcement ratio was 3.58mm. The value dropped to 3.01mm and 2.62 mm at 1.96% and 2.86% reinforcement ratios respectively. This showed that similar to conventional concrete, RGC beams with higher reinforcement content have higher stiffness. This therefore showed that deflection assumptions and code recommendations for conventional concrete can be extended to reinforced geopolymer concrete beams (RGCB).