Development of Geopolymer Concrete Using Waste Marble Sand in Marine Environments

Geopolymer concrete (GPC) has been claimed as one of the sustainable alternatives for the conventional concrete (CC). The GPC mixes prepared with fly ash and other silica and alumina rich pozzolanic mineral binders shows excellent resistance to the chemical ingress into the hardened mass. However, the natural river sand has remained one of important ingredients of the mixture and needs attention. On the other hand, the ordinary concrete faces challenges of sever internal and external chemical degradation when exposed to the marine environments. To address both the issues, it may be interesting to check the feasibility of using waste marble sand in the GPC mixes as the sand alternative and study the chemical ingress scenario of such modified GPC mixtures in the hardened state. This paper focuses on the assessment of the modified GPC specimens subjected to the chloride penetration and acid ingress. The natural river sand of GPC has been replaced from 0% to 60% by weight with the waste marble sand in the mixture to check the feasibility of developing the GPC with reduced natural sand proportion. To resemble the marine environment at the laboratory, the specimen were tested with rapid chloride penetration test and curing with water consisting Sulphuric acid
$(\mathrm{H}_{2}\text{SO}_{4})$
up to 5 % of the volume of the water. Moreover, the modified GPC specimens were subjected to the compressive strength tests also. The tests showed interesting results. The strength properties of the mixes improved with the replacement of the river sand with marble sand up to 40% replacement and beyond a slight decline in the properties was observed. However, the resistance to the chloride ingress was excellent in the modified GPC up to 40% sand replacement. Similarly the surface deterioration of the specimens and loss of mass of modified GPC remained within the acceptable limits. The study encouraged the utilization of the waste marble sand in the GPC mixtures to enhance the sustainability of the mix with improved chemical resistance necessary for the concrete structures in the marine environments.