Effects of cement as a substitute binder on strength and durability of fly ash-rice husk ash geopolymer concrete

Utilization of industrial by-products in concrete is an effective way to reduce the exhaustion of raw materials for concrete production, but it can lead to degradation in concrete properties. Therefore, research efforts are required to achieve a balance between waste utilization and concrete performance. This study examined the strength and durability performance of geopolymer concrete (GPC) developed from fly ash (FA) and fine rice husk ash (FRHA) as main binders (50/50), with partial OPC substitution at different levels (0%-30%). Various properties like workability, compressive strength, water absorption, chloride penetration resistance, carbonation depth, electrical resistivity (ER), and acid attack resistance were experimentally investigated. Results indicated that there was a noticeable improvement in the workability with 20% OPC substitution, achieving the highest slump of 110 mm. The highest compressive strength (50 MPa) was attained with 15% OPC substitution after 90 days. Mix FR85C15 (15% OPC replacement) showed the highest durability performance at all ages through various indicators, that is, water absorption, charge passed, carbonation depth, and ER. Scanning electron microscopy and energy dispersive spectroscopy analyses also validated the enhanced microstructure of FR85C15 compared with other mixes. When exposed to sulfuric acid (H2SO4), Mix FR85C15 showed a minimal loss of 14% in compressive strength. It was concluded that GPC produced using FA and FRHA substituting OPC (up to 15%) can potentially be utilized for structural applications.