Abstract
Compared with nanosilica collected in a gaseous state, nanosilica sol has great economic value and application significance for improving the performance of concrete and mortar. In this study, the influence of nanosilica sol on the hydration process of different kinds of cement is studied by means of hydration heat analysis, X-ray diffraction analysis (XRD) and other methods, and the properties of mortar such as setting time, mechanical properties and porosity are also studied to characterize the influence of nanosilica sol on the macroscopic properties of mortar. The experimental results show that nanosilica sol can accelerate the hydration rate of two kinds of cement and promote the hydration reaction degree of cement, and this promotion effect increases with the increase in nanosilica sol content. At the same time, nanosilica sol can significantly shorten the setting time of the two kinds of cement, and it is more obvious with the increase in content. Excessive content of nanosilica sol will adversely affect the permeability resistance of mortar. It may be caused by the weak interval formed by nanosilica particle clusters in the mortar matrix, which can be supported by the mortar pore structure distribution test. At the same time, the influence of nanosilica sol on the hydration of the two kinds of cement is different, and the compressive strength of HBSAC cement mortar increases first and then decreases after adding nanosilica sol; However, the compressive strength of P·O 42.5 cement mortar increases gradually after adding nanometer silica sol. This shows that nanosilica sol does not effectively promote the hydration of β-C2S in high belite sulfoaluminate cement (HBSAC) mortar. Based on the above experimental results, it can be concluded that when the content of nanosilica sol is about 1%, it has the best promotion effect on the hydration of the two kinds of cement and the performance of mortar.
Highlights
Mineral admixtures have been widely used in concrete for a long time
The results show that [20] compared with calcium silicate hydrate (C–S–H) gel formed by the hydration of cement, C–S–H gel formed by the reaction of nanosilica clusters and calcium hydroxide (CH) has lower binding performance
high belite sulfoaluminate cement (HBSAC) cement, the first exothermic peak is mainly caused by the heat of the hydration heat and dissolution, and the second exothermic peak is mainly caused by hydration in the cement
Summary
Mineral admixtures have been widely used in concrete for a long time. They can effectively improve the microstructure of concrete and further affect the mechanical properties and durability of concrete [1,2,3]. Many researchers have carried out a series of studies on the influence of nanosilica sol on the properties of cement-based materials. Kong [28,29] showed that colloidal silica sol has a good effect on cement hydration and concrete microstructure regulation and has more advantages than nanosilica powder. Properties such as quick setting and hardening, low hydration heat and excellent permeability resistance make high-belite sulphoaluminate cement widely useful in many fields, such as road rapid repair. The different influence laws on the hydration process of the two kinds of cement can be obtained, which has a positive significance for exploring the application of nanosilica sol in different cement-based materials. The influence of nanosilica sol on the macro–micro properties of cement-based materials is revealed
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