Phase change expansion anti-cracking agent for concrete and preparation method of phase change expansion anti-cracking agent

Abstract

The invention relates to a phase-change expansion anti-cracking agent for concrete and a preparation method thereof, and the preparation method comprises the following steps: heating polyethylene glycol to a molten state, adding a mixed expansion agent into the molten state, uniformly mixing, adding graphite-phase carbon nitride, uniformly mixing, putting the mixed material into a vacuum drying oven, and carrying out vacuum adsorption, so as to obtain the phase-change expansion anti-cracking agent for concrete. The polyethylene glycol and the mixed expanding agent are adsorbed in the porous structure of the graphite phase carbon nitride, so that the phase change expansion anti-cracking agent for the concrete is prepared. Wherein the mass percentage ratio of the polyethylene glycol to the mixed expanding agent to the graphite phase carbon nitride is (35-49.5%): (49.5-60%): (1-5%). Different active expanding agents are compounded to form the mixed expanding agent, the calcium expanding agent is high in activity and hydration rate and mainly compensates for early-stage shrinkage of the concrete, meanwhile, M-type and S-type MgO expanding agents with different activities are added, shrinkage of the concrete in the middle and later stages is compensated, and therefore compensation shrinkage of the concrete in all stages is guaranteed, and the concrete quality is improved. And the cracking risk of the concrete is reduced.

Description

technical field [0001] The invention relates to the technical field of building material admixtures, in particular to a phase change expansion anti-cracking agent for concrete and a preparation method thereof. Background technique [0002] Concrete cracking is a common problem in construction engineering. There are two main reasons for concrete cracking: one is the shrinkage deformation caused by volume shrinkage during the hydration and hardening process of concrete, especially after the hydration temperature peak, the rate of concrete temperature drop is too fast and the concrete On the other hand, volume shrinkage will increase the internal tensile stress, and when the internal tensile stress exceeds the ultimate tensile strength of concrete, it will also crack the concrete. Concrete cracking will lead to reduced structural strength, durability and volume stability, so reducing the risk of concrete cracking has always been a problem that the industry needs to solve. [0...

AI Technical Summary

Problems solved by technology

The hydration rate of calcium oxide expansion agent is too fast (1~4d), the heat of hydration is high, and the expansion efficiency is large. It can complete more than 90% of its limited expansion rate in the first 3 days, so that it occurs in the plastic stage of cement-based materials. A large degree of hydration leads to the fact that its expansion performance cannot be effectively exerted in the later stage; calcium sulfoaluminate expansion agents require a large amount of water, and the hydration reaction is mainly concentrated before 14 days. Generally, calcium oxide-sulfur aluminum is often used in practical projects. Calcium Oxide is used together, but it does not have much effect on later contraction compensation; Magnesium Oxide expansion agent has a mild expansion reaction, and the expansion reaction can continue to occur, but the early expansion is small, and it is more suitable for medium and long-term aging (14d to 1 year) It is often used in marine engineering to compensate shrinkage under low water-cement ratio, but the expansion agent needs a lot of water for early hydration and later expansion rate, especially in high-strength concrete with low water-cement ratio, the application limit is greater, and with the With the passage of concrete age, the moisture concentration inside the concrete is getting lower and lower, which seriously restricts the hydration process of the expansion agent and cannot achieve the purpose of compensating for shrinkage

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