A STUDY OF COMPRESSIVE STRENGTH AND SULFURIC ACID AND MAGNESIUM SULFATE RESISTANCES OF GEOPOLYMER MORTAR MADE FROM LOW CALCIUM FLY ASH BLENDED WITH HIGH CALCIUM FLY ASH

Abstract

This research studied the compressive strength, sulfuric acid resistance and
loss of compressive strength due to magnesium sulfate attack of geopolymer
mortar made from low calcium fly ash blended with high calcium fly ash at
the rates of 15%, 25%, and 35% by weight of binder. Liquid to binder ratio
of 0.60 by weight and NaOH concentration of 8 Molar were used. The
compressive strength of geopolymer mortar was determined at the ages of 7,
28, 90, and 180 days. Weight loss of geopolymer mortar due to 3% of
sulfuric acid solution (pH=0.5) was determined. Loss of compressive
strength due to 5% magnesium sulfate solution was also investigated. The
result showed that the compressive strength of geopolymer mortar increased
with the increasing of high calcium fly ash content. Weight loss of
geopolymer mortar due to sulfuric acid attack and loss of compressive
strength due to magnesium sulfate attack also increased when high calcium
fly ash increase. Therefore, the optimum replacement of low calcium fly ash
by high calcium fly ash was 25% by weight of binder.