Understanding the Effect of Waiting for the Dissolution of Sodium Hydroxide in Geopolymer Concrete Mixes

Geopolymer concrete (GPC) can be produced by the chemical activation of industrial by-products and processed natural minerals that contain aluminosilicates with the presence of an alkaline activator. Raw components are one of the critical parameters affecting geopolymer performance. On the other hand, the mixing procedure of geopolymer concrete is not any less important. Few demonstrative constructions have been built using GPC as a greener alternative to Portland cement concrete. Numerous variables affect GPC manufacture, such as raw material specification, activator type and dosage, and curing regimes. Despite the conventions of the building industry, the lack of proper mix design methods limits the wide acceptance of GPC in the industry. This report conducted experimental trials on GGBS-based GPC to optimize a mixing design procedure to achieve best mechanical strength and structural integrity. Geopolymer concrete properties were evaluated through slump and unconfined compressive strength tests. The laboratory trials in this report revealed that all geopolymer mixes, except SD0HV and 1W-SG, exhibited high workability values. Also, the presence of an alkaline activator was vital to attain satisfactory compressive strength values. The alkaline activator could be used when cooled and reached room temperature after two hours of preparation and was not necessary after 24 h. Mix G-(0.5W-S) with a 0.5A.A. (alkaline activator)/precursor (GGBS) ratio, SSA (sodium silicate alternative)/SH (sodium hydroxide with 10 M molarity) ratio of 1:1, and 0.55 W/B (water to binder) ratio is recommended to achieve best mechanical performance and structural integrity.