Modified calcium oxide expansion agent for shrinkage-compensating concrete and preparation method thereof

Abstract

The invention relates to a modified calcium oxide expanding agent for shrinkage-compensating concrete. The agent is obtained by conducting mixing and ball milling on 0.1-20% by mass of modifier and 80-99.9% by mass of calcium oxide expanding agent; the calcium oxide expanding agent is an expanding agent containing free calcium oxide, and the free calcium oxide serves as a stable expansion source playing an expansion role; the modifier is prepared from one of or multiple substances of sodium sulfate or a crystalline hydrate thereof, ammonium sulfate or a crystalline hydrate thereof, ammonium bisulfate or a crystalline hydrate thereof, sodium sulfite or a crystalline hydrate thereof and ammonium sulfite or a crystalline hydrate thereof. The modified expanding agent can lower the early hydration rate of the expanding agent, reduce expansion energy loss in the concrete plastic stage, increase the expanding rate and reduce the contribution degree of the expanding agent to concrete temperature rise at the same time, the phenomenon that the concrete setting time is affected can be avoided, and the slump degree and expansion degree of concrete cannot be lowered. The preparation method is simple, batch production can be conducted, and no toxic dangerous goods are used as raw materials.

Description

technical field [0001] The invention relates to the field of building materials. Specifically, the invention provides a method for preparing a modified calcium oxide expansion agent for shrinkage-compensating concrete with a low early hydration rate and a high limited expansion rate. Background technique [0002] The early volume change of concrete is an important factor causing concrete cracking, mainly including chemical shrinkage, autogenous shrinkage, drying shrinkage and cooling shrinkage of cementitious materials. Among them, reducing concrete cooling shrinkage is the most common way to control concrete cracking, such as adding inert admixtures, stirring with cooling water, reducing the temperature of raw materials, and reducing the reactivity of cementitious materials. However, the calcium oxide expansion agent used for shrinkage compensation concrete has too fast hydration rate during the hydration process, which will generate a large amount of heat in a short period...

AI Technical Summary

Problems solved by technology

[0005] Most of the expansion agents or modified expansion agents of existing concrete will affect the setting time of concrete, and will reduce the slump and expansion of concrete, which is not conducive to concrete construction

[0006] Chinese patent CN103964722A discloses a chemical admixture that improves the performance of concrete expansion agents under restricted conditions. The patent mentions that the use of admixture sodium phosphate salt can improve the limited expansion rate of concrete, but sodium phosphate salt has retarding effects on the concrete cementitious system. role, and the patent does not provide relevant data on the impact of concrete setting time

However, various methods have their limitations at the same time, and better methods need to be studied to improve the performance of calcium oxide expansion agents

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