Analysis of the influence of temperature Control Materials on the Properties of MgO expansion Agent
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Update time : 2023-07-12 09:09:47
Why does concrete crack and shrink?
Concrete is an indispensable building material for the development of today's society. Because of its many advantages, such as easy availability of raw materials, good economy, convenient construction, excellent mechanical properties, good durability, and so on, concrete is widely used in public buildings, civil buildings, water conservancy, traffic engineering, municipal engineering, nuclear power engineering, and other fields, but its primary raw material cement will produce volume shrinkage and release a lot of heat in the process of hydration.
And then cause the shrinkage of concrete, coupled with the environmental impact, and finally lead to the cracking of the concrete structure.
The occurrence of cracks will not only lead to structural leakage, reduce the structure's durability, and increase the maintenance cost but also cause safety problems for the building structure.
Therefore, reducing the shrinkage of concrete is the key to solving the cracking of building structures.
Expansion effect of MgO in concrete
MgO can be used as an expansive agent to compensate for the shrinkage of concrete structures because of its low water demand and a long expansion period. Still, the hydration heat release of the MgO expansive agent will affect its effect.
Therefore, in using the MgO expansion agent, how to reduce the internal temperature of the concrete structure is the key.
What is the temperature control material?
Temperature control materials can delay the hydration of cement and reduce the early hydration heat while not reducing the total hydration heat.
The combined use of WK and MgO expansion agents can better compensate for concrete shrinkage and reduce temperature shrinkage.
After the study, the following conclusions are drawn:
The main results are as follows:
(1) The temperature control material can adjust the hydration heat release rate of MgO expansive agent and reduce the hydration heat; the higher the mold temperature of cement paste, the greater the effect of WK on the hydration heat of cement paste, but it will prolong the setting time; the effect of WK is different under different mold temperature, the amount of WK can be increased appropriately when the mold temperature is lower, and the amount of WK can be reduced when the mold temperature is higher.
(2) The temperature control material can stimulate the hydration of the MgO expansive agent to a certain extent, and the higher the curing temperature is, the more significant the effect is. Under the condition of water culture at 20 ℃ and 60 ℃, the limited expansion ratio of mixed 0.4%WK+6%M-MgO mortar increased by 0.014% and 0.028%, respectively, compared with that of 6%M-MgO alone.
(3) Temperature control materials are disadvantageous to the early compressive strength of cement-based materials mixed with an MgO expansive agent. Still, they can improve the later compressive strength to a certain extent.
(4) The temperature control materials influence the hydration process, the formation rate of hydration products of the MgO expansive agent, and the compactness of cement-based materials can be improved by mixing them.
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