The development of the cement industry is accompanied by the problems of high emissions, high energy consumption, and high pollution. In order to reduce the environmental hazards of the construction industry, the academic community has been looking for green and low-carbon cement substitute materials.
Activated magnesium oxide has become one of the potential cement substitute materials due to its high strength, low emission, low energy consumption, and recyclable characteristics. In this paper, through indoor experiments, the mechanical properties, bonding properties, anti-freeze properties and carbonization depth of active magnesium oxide carbonized concrete are studied. The main conclusions are as follows:
(1) Different dosages (0%, 20%, 35%, 50%) of activated magnesia (CY-Mg30) were used instead of cement, and the compressive strength, splitting tensile strength and Elastic Modulus.
The test results show that the mechanical properties of concrete with 20%, 35% and 50% active magnesia (CY-Mg30) after carbonization are significantly improved compared with ordinary concrete without active magnesia (CY-Mg30); four Under the concrete mix ratio, the concrete with 35% active magnesium oxide (CY-Mg30) content has the highest compressive strength and splitting tensile strength, and the elastic modulus is the largest; when the active magnesium oxide (CY-Mg30) content reaches 50% , Due to insufficient carbonation of activated magnesium oxide (CY-Mg30) hydrate in concrete, the strength of concrete is reduced compared with 35% dosage, so the dosage of activated magnesium oxide (CY-Mg30) should not be too high.
(2) On the basis of the optimal mix ratio of (1), different dosages (0%, 3%, 6%, 9%) of silica fume are used to replace the cement in active magnesia (CY-Mg30) concrete. The active magnesium oxide (CY-Mg30) concrete with silica fume content was tested for compressive strength. The test results show that the compressive strength of concrete increases after the active magnesia (CY-Mg30) cement is mixed with silica fume. The compressive strength also increases, and when the silica fume content exceeds 9%, the concrete strength begins to decrease, and 6% is a more suitable silica fume content.
(3) Through the indoor model test, the bonding properties between ordinary concrete and activated magnesium oxide (CY-Mg30) carbonized concrete were compared with smooth round steel bars and threaded steel bars respectively. The research results showed that activated magnesium oxide (CY-Mg30) concrete and The bonding performance between steel bars is significantly improved compared with ordinary Portland concrete.
(4) Through indoor experiments, the variation law of carbonation depth of activated magnesia (CY-Mg30) concrete under accelerated carbonation conditions was studied, and the mathematical model of carbonation depth of activated magnesia (CY-Mg30) concrete was established according to the test data, and the activated magnesia (CY-Mg30) concrete carbonation depth was established. (CY-Mg30) The conclusion that the carbonation depth of concrete is proportional to the square root of carbonation time.
(5) Test and analyze the water resistance of activated magnesium oxide (CY-Mg30) carbonized concrete, establish the relationship curve between the compressive strength of activated magnesium oxide (CY-Mg30) carbonized concrete and its water content, and analyze the activated magnesium oxide (CY-Mg30) carbonized concrete. Mg30) carbonized concrete has good water resistance. At the same time, several freeze-thaw cycle tests were carried out on activated magnesia (CY-Mg30) carbonized concrete. The test results showed that the mass loss and compressive strength loss of concrete after freeze-thaw cycles were small, and the activated magnesia carbonized concrete had good frost resistance. .