Effect of activator on rheological properties of alkali-activated slag-fly ash pastes

激发剂对碱矿渣-粉煤灰浆体流变性能的影响

The time-dependent rheological behaviors of alkali-activated cement(AAC)are expected to be precisely controlled,in order to meet the requirements of modern engineering practices.In this paper,the effects of activator,including the Na_(2)O concentration and SiO_(2)/Na_(2)O(S/N)molar ratio,on the rheological behavior of alkali-activated slag fly ash pastes were investigated.The small amplitude oscillatory shear(SAOS)and shear test were used to evaluate the structural build-up and flowability of pastes.Besides,zeta potential measurement,calorimetric test and thermogravimetric analysis(TGA)were carried out to reveal the physico-chemical mechanisms behind the rheological evolution of fresh pastes.It was found that high Na_(2)O concentration and low S/N molar ratio improved the flowability and structural build-up rate of paste.Moreover,the structural build-up of alkali-activated slag-fly ash pastes consists of two stages,which is controlled by the dissolution of solid reactants and formation of C-(A)-S-H gels,respectively.

为满足现代工程应用的要求,需要精确控制碱激发水泥(AAC)流变性能的时变特性。本文研究了激发剂Na_(2)O浓度和SiO_(2)/Na_(2)O(S/N)摩尔比对碱激发矿渣-粉煤灰浆体流变性能的影响。采用小幅震荡剪切测试(SAOS)和旋转剪切法评价了浆体的结构构筑和流动性。通过zeta电位测定、等温量热分析和热重分析,揭示了新拌浆体流变性能演化的物理化学机理。结果表明,高Na_(2)O浓度和低S/N摩尔比提高了浆体的流动性和结构构筑速率。碱矿渣-粉煤灰浆体的结构构筑分为两个阶段,分别受固体反应物溶解和C-(A)-S-H凝胶形成的控制。