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

The aim of present study is to investigate the potential application of groundnut shell ash (GSA) in alkaliactivated 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 mu m, 6.5 mu m, 8.0 mu m), the compressive strength of AAS pastes at 28 d will slightly decrease, but the shrinkage properties will be improved.