An investigation on the effect of sea sand on the properties of fly ash geopolymer mortars

The global consumption of river sand as a fine aggregate in the production of concrete and mortar is very high. Unfortunately, in the last 20 years, the obtainability of river sand is reducing and several countries have problems in supplying. One option to solve the scarcity of river sand is to use sea sand in the construction field. In the current paper, an attempt has been done to investigate the effect of different ratios of untreated sea sand on the compressive strength and durability of fly ash (FA) based geopolymer mortars activated with sodium silicate. The ratio of fine aggregate to binder was 2:1. River sand was replaced with sea sand at levels of 25%, 50%, 75% and 100%, by weight. The compressive strength and percentage of water absorption at the ages of 7, 28 and 120 days were measured. The rapid chloride permeability test (RCPT) was determined at the age of 28 days. Selected mortar specimens were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and its derivative (DTG) as well as scanning electron microscopy (SEM). The results showed that the incorporation of sea sand into FA-based geopolymer mortars has a negative effect on the compressive strength as well as the percentage of water absorption and charge passed. As the content of sea sand increased as the deterioration increased.