Low-heat micro-expansion composite cement and preparation method thereof

Abstract

The invention relates to a low-heat micro-expansion composite cement and a preparation method thereof. The composite cement comprises the following components: 1-8 parts of a magnesium oxide expanding agent, 25-70 parts of industrial waste residue, 25-70 parts of portland cement clinker, and 1-4 parts of gypsum. The preparation method includes: mixing and grinding the magnesium oxide expanding agent, the portland cement clinker and the gypsum to prepare magnesium oxide expansive cement with a specific surface area of not lower than 300m<2> / kg, then mixing the magnesium oxide expansive cement with the industrial waste residue evenly according to the ratio to prepare composite cement; or burdening and mixing the magnesium oxide expanding agent, the cement clinker, the gypsum and the industrial waste residue in proportion, and carrying out grinding together to obtain composite cement. The composite cement prepared by the method has fineness of 80-micrometer square hole screen residue of less than 10%, and a specific surface area of not less than 300m<2> / kg. The composite cement provided by the invention can generate expansion in the early stage, also can generate expansion in the middle and late stage, simultaneously satisfies compensation of concrete shrinkage in the early stage and the middle and late stage, and prevents shrinkage crack of concrete.

Description

technical field [0001] The invention belongs to the technical field of building materials, and in particular relates to a low-heat, micro-expansion composite cement and a preparation method thereof. Background technique [0002] Concrete is one of the most widely used building materials. In the process of hardening to generate strength, concrete will produce various shrinkages due to cement hydration or loss of moisture to the external environment, such as autogenous shrinkage, drying shrinkage, and temperature drop shrinkage. Under constraint conditions, shrinkage will generate tensile stress. When the tensile stress exceeds the tensile limit of the concrete material, it will cause the concrete material to crack, thereby affecting the service life and safety of the concrete building structure. With the development of my country's economy and society, the demand for infrastructure construction continues to increase, and a large number of major infrastructure construction pr...

AI Technical Summary

Problems solved by technology

However, for relatively small-scale mass concrete, the temperature drop shrinkage occurs relatively early, because the magnesium oxide in the cement clinker cannot effectively compensate, especially for the autogenous shrinkage that occurs in the early stage, the compensation effect is better. Difference

On the other hand, due to the problem of cement stability, the content of magnesium oxide in cement clinker cannot exceed 5%, so the content of magnesium oxide is often insufficient, and the expansion cannot fully compensate the shrinkage

Later research developed magnesium oxide with different hydration activities and used it as an external expansion agent. Its dosage and expansion performance can be better controlled, but its dispersion uniformity in concrete is difficult to ensure, and the mixing time is increased.

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