Core-shell structure expansion agent for concrete and preparation method thereof

Abstract

The invention relates to a core-shell structured expanding agent for concrete. The core-shell structured expanding agent comprises 55-76% of calcium oxide, 7-12% of a high-modular polymer, 1-5% of azodiisobutyronitrile, 3-6% of 3-aminopropyl methyldiethoxy silane, 2-4% of sodium hexametaphosphate, 2-4% of sodium silicate and 9-14% of ferric chloride. According to the preparation method of the expanding agent, anhydrous dichloromethane solution of the high-molecular polymer and ethanol solution of the 3-aminopropyl methyldiethoxy silane are added into the calcium oxide in sequence; the azodiisobutyronitrile is added to complete surface graft modification; and finally sodium hexametaphosphate solution, sodium silicate solution and ferric chloride solution are added and roasting is carried out through a muffle furnace to prepare the core-shell structured expanding agent. The expanding agent is uniform in particle size; a ferric oxide shell is capable of preventing calcium oxide expandingagent from too fast early-stage hydration, the ferric oxide undergoes reaction with alkali liquor in the concrete to generate ferric hydroxide to provide a secondary expanding source, so that the problem of effectively compensating shrinkage is solved; and according to the expanding agent, the compactness of the concrete is increased and the compressive strength and impervious performance of the concrete are improved.

Description

technical field [0001] The invention relates to the technical field of concrete admixtures, in particular to a core-shell structure expansion agent for concrete and a preparation method thereof. Background technique [0002] Calcium oxide (CaO) is an important inorganic expansion agent raw material. In concrete, it is mainly used to react with water to form calcium hydroxide with low solubility under the condition of less water demand, and at the same time, it produces greater expansion. Can, compensate for early concrete shrinkage, thereby reducing the probability of cracks. Since the reaction between calcium oxide and water is very violent, it can release high reaction heat instantly when it contacts with water. The large heat release makes the internal temperature of concrete rise faster, but the internal heat dissipation is slow, and the surface cooling speed is very fast, resulting in temperature stress. , temperature cracks appear, and because of the high reactivity o...

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Problems solved by technology

For example, the invention with the patent number 201510060677.9 "a modified calcium oxide expansion agent for cement concrete" coats the surface of the expansion agent with long-chain fatty acids, but only simply solves the problem of rapid reaction of calcium oxide, but the expansion agent lacks The secondary expansion source is still not ideal for fully improving the crack resistance of concrete

Another example is the patent No. 201510061056.2 of the invention "A Modified Calcium Oxide Cement Concrete Expansion Agent and Its Preparation Method". The material is wrapped on the surface of calcium oxide, and it also lacks the secondary expansion source

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