Comparison between the Compressive Strength of Binary and Ternary Alkaline-activated Pozzolanic Concrete

Abstract

This research compared the compressive strength of binary and ternary alkaline-activated pozzolanic concrete. Rice husk ash (RHA) and Metakaolin (MK) combined partially with Ordinary Portland Cement (OPC) each are the binary concrete while the combination of rice husk ash and metakaolin (RHA/MK) combined partially with OPC is the ternary concrete. The OPC was replaced at 15% each with RHA, MK and RHA/MK in ratios 0.33 (X), 0.5 (Y) and 1.0 (Z) of sodium silicate (NS) to sodium hydroxide (NH) as activator. A mix design ratio of 1:2:4 and water-cement ratio of 0.65 with alkaline liquid to pozzolan of 0.30 was used in the process of the study. Physical properties of the constituent materials as well chemical analysis of pozzolans were determined. Slump and compacting factor tests were done on the freshly mixed concrete to determine their workability while compression test was performed on the hardened concrete cube samples of side 150mm to obtain the compressive strength. Curing was done for 7 and 28 days inside water tank. The result of the compression test showed that the compressive strength of the ternary concrete continuously increased as the sodium silicate to sodium hydroxide ratio increased. At the maturity age of 28days, the values of the compressive strength were 14.2 MPa, 17.5 MPa and 20.3 MPa for sodium silicate (NS) to sodium hydroxide (NH) ratios of 0.33, 0.5 and 1.0 respectively. These values are higher than the compressive strength for the binary concrete of RHA and MK taken separately for the same NS to NH ratios which at 28days curing age were 10.9 MPa, 14.8 MPa, 16.2 MPa for RHA and 14.0 MPa, 15.3 MPa, 18.2 MPa for MK. The result of the research can be used in the construction industry for normal concrete work as well as serve for effective waste disposal of agricultural waste products such as RHA and MK to reduce environmental pollution.