Preparation method and application of composite magnesium oxide expanding agent

Abstract

The invention discloses a preparation method and application of a composite magnesium oxide expanding agent, and belongs to the technical field of preparation of concrete special functional materials.The preparation method specifically comprises the following step: calcining a dolomite and serpentine mixture with a specific ratio at the temperature of 1050-1150 DEG C for 60 minutes to obtain thecomposite magnesium oxide expanding agent. The obtained composite magnesium oxide expanding agent has high volume expansion rate, the reaction activity of the composite magnesium oxide expanding agentis reduced along with increasing of the calcination temperature, and the composite magnesium oxide expanding agent is mainly used for compensating long-term shrinkage of mass concrete. The preparation method provided by the invention not only can greatly reduce the production cost of the magnesium oxide expanding agent, but also can treat industrial tailings and realize resource utilization.

Description

technical field [0001] The invention belongs to the technical field of preparation of concrete special functional materials, in particular to a preparation method and application of a composite magnesium oxide expansion agent. Background technique [0002] During the molding and hardening process of concrete, volume shrinkage will occur due to the hydration and drying loss of cementitious materials, temperature changes and other reasons. When the component is constrained, internal stress will be generated inside the concrete, and cracks will occur when the internal tensile stress is greater than the tensile strength of the concrete. Shrinkage cracking of mass concrete will reduce the physical and mechanical properties of concrete structures, which is a major concern in the field of concrete engineering. Add magnesium oxide expansion agent to the concrete. Magnesium oxide hydrates to form magnesium hydroxide crystals during the hydration and hardening process of concrete. Ma...

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Problems solved by technology

However, in the existing technology of preparing magnesium oxide expansion agent by replacing part of magnesite with dolomite, there is also a large amount of calcium oxide in the product. The early hydration of calcium oxide is too rapid, it is difficult to produce effective expansion inside the hardened concrete, and it may damage the The problem of the slurry structure of the initial cementitious material with low strength

[0005] Xu Lingling et al. used dolomite and serpentine to prepare magnesia expansion agent. The calcination temperature was higher than 1200°C, and the calcination time was 2h. The magnesia content in the fired expansion agent was higher than 50%, but the activity was extremely low (using the current Measured by the standard method, the activity index is higher than 500s), and the expansion time at 40°C is 80 days later, and the ability to compensate for the shrinkage of ordinary concrete structures is very low

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