Utilization of groundnut shell ash in alkali-activated slag: Comparison of hydration, shrinkage and compressive strength

Abstract

The aim of present study is to investigate the potential application of groundnut shell ash (GSA) in alkali-activated slag (AAS). The effect of GSA incorporation on the hydration, shrinkage, and compressive strength of AAS was examined. It was found that laboratory-prepared GSA has a high content of alkali oxides such as CaO or K2O, providing additional alkali activators for the AAS system. When the sodium oxide (Na2O) equivalent of alkali activators is 4%, GSA has a positive effect on the hydration of AAS, leading to a 31.2% increase in cumulative heat at 72 h, and a 20.0% increase in compressive strength at 28 d. When the Na2O equivalent of alkali activators is 6%, the addition of GSA(5%) reduced the autogenous shrinkage of the pastes by 12.0%. Incorporation of GSA causes a decrease in pastes fluidity, and within a certain substitution range (≤10%), the setting time was prolonged. With the increase of the average particle size of GSA (4.2 µm, 6.5 µm, 8.0 µm), the compressive strength of AAS pastes at 28 d will slightly decrease, but the shrinkage properties will be improved.