Abstract
Geopolymer results from the reaction of a source material that is rich in silica and alumina with alkaline liquid. It is essentially cement free concrete. It is a type of amorphous aluminosilicate cementitious material which can be synthesized by polycondensation reaction of geopolymeric precursor and alkalipolysilicates. In this work an attempt is made to develop the mix proportion for geopolymer concrete grades and relative comparison has been made with equivalent mix proportions of grades of OPC Concretes in heat cured conditions. Therefore, rice husk and kaolin brought from local sources, after burnt ash at 650ºC and 750ºC respectively. Furthermore, sodium hydroxide and sodium silicate were mixed together to form alkaline activator solutions, and aggregate grading based. Based on experimental tests the optimum coarse aggregate/total aggregate and total aggregate/cement ratios were found to be 0.55, 0.57, 0.60, 0.58, 0.54 & 0.63 and 5.7, 5.6, 5.52, 4.62, 4.56 & 4.47 at an optimal mix ratio of trial mix 1 to trial mix 6 was 1:2.6:3.1, 1:2.4:3.2, 1:2.2:3.3, 1:1.8:2.7, 1;2.0:2.4 & 1:1.5:2.8 respectively. The concrete compressive strength at 28 days using a mix 4 of mix ratio is 1:1.8:2.7 for the local available materials was found to be 55.03N/mm² GPC as compared with the minimum compressive strength of 54.03N/mm² of OPC. However, the flexural strength at 28 days corresponding to the experimental optimal was 5.81N/mm² with water‐cement ratio of 0.50. Therefore, strength test has been carried out on both compressive and flexural strengths for all the parameters and the maximum compressive strength for all mixes shown that results of GPC of G25, G30, G35, 40, 45 and G50 were equivalent to M25, M30, M35, M40, M45 and M50 of OPC respectively. The findings of this study suggest that, using the proposed method GPC can be produced for a specific strength by employing the corresponding AAS/FA ratio obtained from the modified strength vs. w/c ratio curve. GPC can also be produced for a specific AAS/MK ratio to achieve the corresponding strength.
