Rice husk ash for alkali activation binary blends (fly ash/blast furnace slag)

ABSTRACT Alkali activated mortars made of class F fly ash and blast furnace slag were cast, in order to study the effect of an alternative source of silica on its properties of fluidity and compressive strength. Rice husk ash and sodium silicate solution, mixed with sodium hydroxide, were used for activation of mortars. The mineralogical and structural information of alkali activated systems was obtained by X-ray diffraction (XRD), while the analysis of fresh properties was carried out by means of fluidity test. The mechanical properties of mortars were assessed by 28 days compressive strength test. It was found that mortars activated with rice husk ash plus sodium hydroxide showed compressive strengths up to 25% higher that those activated with sodium silicate / sodium hydroxide. Finally, equations were proposed for the prediction of compressive strengths of mortars according to the type of activator. This study concludes that it is possible the use of rice husk ash as an alternative source of silica in alkaline activation process.摘要：以F级粉煤灰（class F fly ash）与高炉矿渣为原料制备碱激发砂浆（alkali activated mortars），旨在探究替代性硅源对其流动性与抗压强度性能的影响。本研究采用稻壳灰以及掺混氢氧化钠的硅酸钠溶液作为砂浆的激发剂。通过X射线衍射（X-ray diffraction, XRD）获取碱激发体系的矿物学与结构信息，借助流动度试验分析鲜态砂浆的工作性能，并通过28天抗压强度试验评估砂浆的力学性能。研究发现，采用稻壳灰与氢氧化钠复配激发的砂浆，其抗压强度较仅以硅酸钠-氢氧化钠为激发剂的砂浆最高提升25%。最后，本研究提出了基于激发剂类型预测砂浆抗压强度的计算公式。本研究证实，稻壳灰可作为替代性硅源应用于碱激发工艺中。