The Effects of Different Types of Nano-Silicon Dioxide Additives on the Properties of Sludge Ash Mortar

摘要

To improve the drawbacks caused by the sludge ash re-placement in mortar, the previous studies have shownthat the early strength and durability of sludge ash/ce-ment mortar are improved by adding nano-silicon diox-ide (nano-SiO_2) to mortar. In this article, three types ofnano-SiO_2SS, HS, and SP (manufacturer code names)—were applied to sludge ash/cement mixture to make pasteor mortar specimens. The object is to further extend therecycle of the sludge ash by determining the better type ofnano-SiO_2 additive to improve properties of sludge ash/cement paste or mortar. The cement was replaced by 0,10, 20, and 30 of sludge ash, and 0 and 2 of nano-SiO_2additives were added to the sludge ash paste or mortarspecimens. Tests such as setting time, compressivestrength, scanning electron microscopy, X-ray diffrac-tion, nuclear magnetic resonance, and thermogravimetricanalysis/differential thermal analysis were performed inthis study. Test results show that nano-SiO_2 additives cannot only effectively increase the hydration product (cal-cium silicate hydrate C-S-H gel), but also make the crys-tal structure denser. Among the three types of nano-Si02additive, the SS type can best improve the properties ofsludge ash/cement paste or mortar, followed by the SPand HS types.