Mechanical, microstructural and leachability characteristics of ternary geopolymer mortar: a step towards carbon neutral materials

With rising carbon loads on the environment and the need to support infrastructure development in developing countries, using traditional building materials without disrupting the ecosystem has become a challenge. Several initiatives have been implemented and are continuously being considered to alleviate the current situation. Hence, the current study attempts to reinforce the utility of geopolymer mixes by investigating mechanical properties of ternary geopolymer mortar along with microstructural examination. Blend A, which contains Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBS), and Metakaolin (MK), and Blend B, which contains FA, GGBS, and Rice Husk Ash (RHA) in varying proportions, have been made with Natural River Sand (NS). Another set of comparable mixes containing Foundry Sand (FS) was also tested to build a performance comparison and propose a possible replacement option for natural river sand in construction. Experimental observations revealed superiority of blend A in mechanical strength over blend B. Also, foundry sand proved to produce mixes with lesser strength in comparison to natural sand mixes. However, all samples with FS were seen to fulfill the minimum strength criteria laid down by IS 2250: 1981. Microstructural tests such as Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX) were also carried out to establish reasoning in the strength variation shown by various blends. The concentration of heavy metals leached out in conformity with APHA 3120 was also tested to analyze the environmental impact of such innovative blends, and no combination was found to leach out heavy metals over the acceptable threshold. The outcomes of the study, thus support the usage of ternary geopolymer mixes over unary and binary mixes for high-quality precast member production.