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Effects of nano-SiO2 on consistency, setting time, early strength and shrinkage of composite cement paste

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Document pages: 8 pages

Abstract: This study summarizes the raw materials and mix proportion of composite cement paste prepared by adding silicon based micro particles and nano particles. The effects of amorphous nano-SiO2 on early properties, including consistency, setting time, early strength, chemical shrinkage and self shrinkage, were studied. With the same dosage of superplasticizer, the consistency of Nano-SiO2 cement paste is higher than that of silica fume cement paste. It was observed that the initial and final setting time were significantly shortened, especially in the nano-SiO2 addition group. The time difference between the initial and final setting time increased with the increase of the proportion of Nano-SiO2. The addition of Nano-SiO2 is more helpful to improve early agingrengths of the paste with or without fly ash admixed than silica fume additive for the same mass proportion. Both the chemical and autogenous shrinkages of cement paste develop with the increasing amount of micro- or nanolevel silica particles; however, nano-SiO2 plays a more active role than silica fume in inspiring early-age shrinkage. The physical and chemical mechanisms of nano-SiO2 in cement paste are also discussed.

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