Influence of Composition Parameters, Curing Conditions and Salt Solutions on Geopolymer Concrete Properties.(Dept.C)

Abstract

The growing demand for environmentally friendly construction has been the driving force behind the production of sustainable and cost-effective construction materials. Portland cement (PC), which is not considered an environmentally friendly material, is an important ingredient in concrete. In contrast to Portland cement, geopolymers are gaining increased interest as low-CO2 emission binders. This research consists of two basic stages, the first stage investigates the effects of many parameters on the properties of geopolymer concrete based on fly ash, in particular the compressive strength, tensile strength, and flexural strength .The parameters included were fly ash content, degree of solution molarity, alkaline liquid ratio to fly ash content, curing conditions, fine aggregate to coarse aggregate ratio. Second stage of the research concerned with the durability of geo-polymer concrete developed using fly ash class-F. As a guide for assessing the durability of geo-polymer concrete, the efficiency of ordinary Portland cement (OPC) concrete is also discussed. The influence of salt solutions of different concentrations through various periods of wetting – drying cycles on the weight loss, water absorption, and geo-polymer concrete has been investigated for its compressive strength. According to the first stage results, the best parameters which gave the highest geo-polymer concrete's mechanical properties, were: fly ash content of 400 kg/m3, 16 M degree of molarity, curing time of 3 days in oven, the ratio of alkaline liquid to the content of fly ash equals 0.5 and ratio of fine aggregate to coarse aggregate equals to 1:2, where the compressive strength reached its highest value (387 Kg/cm2). The results of second stage revealed that geopolymer concrete is less affected than cement concrete with respect to compressive strength and more affected in weight loss and water absorption. Geopolymer concrete showed an increase in water absorption compared to OPC concrete, after 9 weeks of wetting – drying cycles in salt solutions, by about 176% &184% for 5% & 10% solutions concentration, respectively. Also, more weight loss for geopolymer concrete specimens was revealed compared to OPC concrete by about 33% & 30% for 5% & 10% solutions concentration, respectively. However, the geopolymer concrete (GPC) showed less reduction in compressive strength due to the exposure to salt solutions (wet – dry cycles) than OPC. For both solution concentrations (5% & 10%), the average reductions in GPC compressive strength were 18%& 25%, respectively, while the corresponding reductions in OPC were 25% & 34%.