The influence of curing temperature on the medium-temperature performance of corundum castable
author: XINTAI
2025-07-17
The hydration performance of CAC is influenced by many factors, such as temperature, humidity, water-cement ratio, micro-powder and additives, etc. Among them, temperature not only affects the types of CAC hydration products, but also influences its hydration process (dissolution-precipitation process), which may further affect the performance of the castable. During the heating process, the hydration products of cement undergo dehydration and decomposition reactions, which damage the internal structure of the castable and result in significant strength loss of the castable at 400 to 1000 degrees Celsius. Due to the temperature gradient of the castable during baking and use, the castable lining is prone to peeling off at 400 to 1100℃. Moreover, the construction of castable materials lasts throughout the year, so the construction temperature varies greatly.
The room temperature flexural strength and compressive strength of castable material samples after curing at different temperatures and heat treatment. It can be seen that:
(1) Both the demolding strength and the strength after heat treatment of the castable increase with the increase of the curing temperature. In the curing temperature range of 5 to 25℃, the increase in demolding strength and strength after heat treatment at different temperatures is not very obvious. The demolding strength of the castable samples cured at 40 and 50℃ and the strength after heat treatment at different temperatures increased significantly compared with the strength of the castable samples cured at a lower temperature.
(2) When the heat treatment temperature is increased from 110℃ to 800℃, the strength of the castable sample decreases.
With the increase of curing temperature, the hydration degree of CAC increases, the amount of hydration products increases, and the cementization degree of each component in the castable is enhanced. Therefore, the demolding strength and drying strength of the castable increase with the rise of the curing temperature. The hydration products decomposed during the heat treatment process, generating pores and microcracks. Therefore, the strength of the sample after heat treatment at 800℃ decreased compared to that after drying. The in-situ generation of CA₂ in the sample after heat treatment at 1100℃ increased the degree of combination of each component. Based on Figure 2, it can be inferred that as the curing temperature rises, the amount of hydration products increases, and the distribution of hydration products may become more uniform, with the residual CAC particle size decreasing. During the heat treatment process, the calcium source (CaO) after the decomposition of hydration products reacts in situ with Al₂O₃ in the matrix and Al₂O₃ at the edge of the aggregate to form CA and CA₂, which enhances the binding degree between matrices and matrices as well as between matrices and aggregates, thereby increasing the medium-temperature strength. Therefore, as the curing temperature rises, the medium-temperature strength of the castable sample also increases.
The influence of curing temperature on the distribution of hydration products and the in-situ synthesis of CAC can be seen as follows: when the castable is cured at a lower temperature, the hydration amount of calcium aluminate cement is small, and the dispersion degree of hydration products is low. When the castable is cured at a higher temperature, the amount of hydration products increases and can be evenly distributed at the edges of the matrix and aggregates through the hydration process (dissolution-precipitation process), reducing the residual particle size of CAC and enhancing the demolding and drying strength of the castable. During the baking process, the hydration products dehydrate and decompose, and react in situ with Al₂O₃ in the matrix and Al₂O₃ at the edge of the aggregate to form CA and CA₂, which enhances the bonding strength between the aggregate and the matrix, thereby increasing the medium-temperature strength of the castable.
Conclusion
(1) With the increase of curing temperature, the amount of hydration products of calcium aluminate cement increases. Due to the dissolution-precipitation process during the hydration of CAC, the uniform distribution of hydration products is promoted, and the residual particle size of CAC is reduced.
(2) As the curing temperature rises, the demolding strength and drying strength of the castable are enhanced, which indirectly reflects the increase in the hydration degree of calcium aluminate cement and the uniform distribution of hydration products. (3) The increase in curing temperature promotes the generation and uniform distribution of CA₂ during the heat treatment process, thereby leading to an increase in the medium-temperature strength of the castable.
(1) With the increase of curing temperature, the amount of hydration products of calcium aluminate cement increases. Due to the dissolution-precipitation process during the hydration of CAC, the uniform distribution of hydration products is promoted, and the residual particle size of CAC is reduced.
(2) As the curing temperature rises, the demolding strength and drying strength of the castable are enhanced, which indirectly reflects the increase in the hydration degree of calcium aluminate cement and the uniform distribution of hydration products. (3) The increase in curing temperature promotes the generation and uniform distribution of CA₂ during the heat treatment process, thereby leading to an increase in the medium-temperature strength of the castable.
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