A kind of compact anti-cracking agent for concrete

Abstract

The invention discloses a concrete compaction anti-cracking agent which comprises 20.0-60.0% of light calcined magnesia, 10.0-30.0% of calcium oxide-calcium sulfoaluminate double-expansion source expanded clinker, 5.0-15.0% of gypsum and 20.0-50.0% of a fine powder material of which the specific surface area is greater than 300m<2> / kg, wherein the sum of the contents of all components is 100% based on the total mass of the concrete compaction anti-cracking agent. The concrete compaction anti-cracking agent can be used in concrete to effectively inhibit shrinkage of the concrete and improve the compactness and the durability of the concrete.

Description

technical field [0001] The invention belongs to the field of building material admixtures, and in particular relates to an admixture used for concrete, a high-performance dense anti-cracking agent for preventing cracks in concrete. Background technique [0002] For concrete-based buildings, since the concrete itself will shrink, and the external temperature change will also affect the building, it will cause cracks in the concrete-based building. Building cracks have a direct impact on the durability of buildings. If it is not controlled, it may even cause the danger of building collapse. [0003] From the material point of view, concrete expansion agent, shrinkage reducer, steel fiber and synthetic organic fiber are all effective measures to reduce or disperse cracks. But in terms of material price and construction convenience, expansion agent has more advantages. Cracks in buildings are mainly caused by shrinkage of concrete. Providing concrete expansion agent to compen...

AI Technical Summary

Problems solved by technology

[0006] The main disadvantages of ettringite expansion agents are: (1) The hydration is fast, and the expansion mainly occurs before 14 days, which has little compensation for the later shrinkage of cement-based materials; the expansion performance is poorly adjustable, and cannot be adjusted according to the shrinkage of the target concrete (2) The thermal stability of ettringite is poor, and it is easy to decompose under the condition of 80 ℃; (3) The ettringite expansion agent has high water demand, and the requirement for curing humidity is too high, and it is usually difficult for engineering maintenance. Meet the maintenance requirements of ettringite expansion agents

[0007] Calcium hydroxide expansion agents also have the disadvantages of too fast expansion and poor adjustability in the expansion process. Under summer construction conditions, the expansion energy of a day usually responds by more than 80%, which is difficult to compensate for the temperature drop and shrinkage of concrete and the later drying shrinkage, and its expansion Source Ca(OH) 2 Under the action of pressure water, the solubility is also greater

Therefore, the application of existing concrete expansion agents based on these two expansion sources in hydraulic engineering, marine engineering or concrete engineering with erosive media (sulphate) is limited, and it cannot effectively compensate for the shrinkage of concrete under construction conditions in summer.

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