Comparative Experimental Study of Sustainable Reinforced Portland Cement Concrete and Geopolymer Concrete Beams Using Rice Husk Ash

The ordinary Portland cement (PC) manufacturing process emits toxic carbon dioxide into the environment. Minimizing cement consumption in the construction industry is a major scholarly priority. This paper studies the comparison of reinforced Portland cement concrete and geopolymer concrete beams, in which rice husk ash (RHA) is used as a partial replacement for cement. The study aims to determine the optimum mix proportion of Portland cement concrete with RHA (PC-RHA) and geopolymer concrete with RHA (GC-RHA) for compressive strength that meets the requirements for normal strength concrete of 18, 25, and 32 MPa and compares to ones of the control PC without RHA. Then, the load behaviors and the failure modes of the reinforced PCC beam and reinforced GC beam using RHA as partially PC (PC-RHA beam and GC-RHA beam) were investigated. The obtained experimental load capabilities were also compared to ones predicted by the equation for designing reinforced concrete beams developed by ACI Committee 318. According to the test results, the compressive strength of the PC-RHA and GC-RHA decreased when there was a higher proportion of RHA replacement in the concrete. In terms of the structural behavior, all the PCC, PC-RHA, and GC-RHA beam curves are bilinear up to the first crack load and before the yield load, then become nonlinear after the yield load of the beam specimens. The maximum crack width of the GC-RHA beam was less than that of the PC-RHA beam. Furthermore, the GC-RHA beam was more ductile than the PC-RHA beam. Finally, the ACI equation provides reliable predictions with a margin of error of 4 to 7%. This concludes that the experimental load capabilities of the PC-RHA beam and GC-RHA beam were consistent with the ACI design equation.