Absorption capacity and porosity percentage of geopolymer concrete with varying percentage of source material and alkalinity ratio

Abstract

The main objective of this study is to determine the absorption capacity and porosity characteristics of geopolymer concrete with the variation in percentage of source material such as fly ash of 350 kg/m3, 450 kg/m3 and 550 kg/m3 respectively. Twelve mixes with different alkaline liquid (NaOH/Na2SiO3) ratio from 2 to 3.5 with increment of 0.5 was considered for evaluation. The quantity and effect of sodium hydroxide and sodium silicate in these twelve mixes were considered for evaluating the characteristics of concrete. M - Sand was used as fine aggregate and recycled coarse aggregates were taken for this study. Cube specimens of 150 mm × 150 mm × 150 mm were cast and cured at 60°C temperature with oven curing for 24 hours. It was found that absorption percentage of concrete increases by increase in porosity. And compressive strength of concrete gets increases by increase in percentage of porosity up to alkaline ratio 2.5 beyond that more increase in porosity reduces the strength of concrete. It was found that absorption and porosity percentage of mixes increase with increase in source material. Thus compared to 350 kg/m3 of flyash, 550 kg/m3 of flyash shows enhanced compressive strength results. More compressive strength was achieved with mixes of alkaline liquid ratio (NaOH/Na2SiO3) and source material 550 kg/m3. Since more amount of NaOH and water were added to these mixes compared to other mixes and more amount of alumina and silica present in source material helps to enhance the polymerization process. Increase in more percentage of alkaline liquid (NaOH/Na2SiO3) ratios reduces the strength of concrete due to more liberation of heat.