Modified calcium sulfoaluminate-calcium oxide concrete expansion agent and preparation method therefor

Abstract

The invention discloses a modified calcium sulfoaluminate-calcium oxide concrete expansion agent and a preparation method therefor and belongs to the technical field of production of compound concreteexpansion agents. The modified calcium sulfoaluminate-calcium oxide concrete expansion agent specifically comprises a calcium sulfoaluminate-calcium oxide expansion clinker and a modifier which are in a weight-ratio addition level of (80 to 90): (10 to 20), wherein the modifier is prepared from the following ingredients in parts by weight: 30-40 parts of sodium silicate, 10-15 parts of silane coupler, 10-15 parts of carboxymethyl cellulose, 5-10 parts of nano calcium carbonate and 20-45 parts of anhydrous ethanol. According to the modified calcium sulfoaluminate-calcium oxide concrete expansion agent and the preparation method therefor, through optimizing a proportioning ratio of green stock, the ratio of calcium sulfoaluminate to free calcium oxide in the expansion clinker can be in therange of (30: 50) to (50: 30); meanwhile, through modifying the expansion clinker with the modifier, the hydrating speed of the calcium oxide is lowered; and volume expansion resulting from hydrationof the calcium sulfoaluminate also plays a certain role in compensating later-stage contraction deformation of concrete, the volume of the concrete can be continuously and uniformly expanded, early-stage and later-stage contraction of the concrete can be effectively compensated, and thus, the strength of a concrete structure is guaranteed.

Description

technical field [0001] The invention relates to the technical field of composite concrete expansion agent production, in particular to a modified calcium sulfoaluminate-calcium oxide concrete expansion agent and a preparation method thereof. Background technique [0002] Concrete is a heterogeneous and brittle material. After pouring, the cement will emit a large amount of heat of hydration during the hydration process. Since the heat cannot be dissipated quickly, tensile stress will be caused on the surface and inside. When these tensile stresses exceed the limit of concrete When the tensile strength is increased, cracks will appear. Experimental research and engineering application show that introducing a certain amount of expansion agent into concrete can produce moderate expansion, which can effectively eliminate or reduce the shrinkage of concrete. At present, the most widely used expansion agents mainly include sulfoaluminate, calcium oxide and composite expansion age...

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Problems solved by technology

[0003] Calcium sulfoaluminate expansion agents use sulfoaluminate as the main component, and volume expansion occurs during hydration to generate ettringite. For example, Chinese Patent No. CN92105187.5 discloses a sulfoaluminate expansion agent and its manufacturing method; However, a large amount of free water is required during the reaction between alunite and anhydrous gypsum to form ettringite. If the later maintenance is not in place, the ettringite will dehydrate and shrink, causing the effect of first expansion and then shrinkage, which will affect the strength of concrete.

[0004] Calcium oxide expansion agents mainly compensate for concrete shrinkage and deformation through the volume expansion produced during the hydration of calcium oxide to calcium hydroxide. For example, Chinese Patent No. CN201010101520.3 discloses a preparation method of calcium oxide expansion agents. The hydration product The water demand is small, the expansion efficiency is high, and the expansion rate is fast. However, due to the fast hydration reaction rate, a large amount of expansion energy is released in the early stage, and no effective precompression stress can be formed. concrete strength

[0005] Calcium sulfoaluminate-calcium oxide composite expansion agent is obtained by mixing the two in a certain proportion or directly calcining through batch calculation. For example, Chinese Patent No. CN201811078483.1 discloses a preparation method of concrete composite expansion agent. Sulfur-fixed ash, fly ash, magnesium slag, phosphogypsum, lime and bauxite are used as raw materials to prepare a concrete composite expansion agent; the composite expansion agent combines the respective advantages of calcium sulfoaluminate expansion agent and calcium oxide expansion agent, but The deficiencies of the two have not been significantly improved, and there are still problems such as rapid hydration and expansion in the early stage, unstable expansion performance in the long-term age, and increased shrinkage in the later stage, which cannot compensate for the late shrinkage of concrete.

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