Influence mechanism of 1,2-propanediol on the mortar performances cured under the negative temperature condition

In the permafrost regions, the curing process of bored pile concrete is conducted under negative temperature. This curing condition significantly impedes the development and formation of the concrete performances. 1,2propanediol (1,2-PPD) is widely recognized as an excellent refrigerant and deicing agent in industrial applications, but its utilization in concrete remains infrequent. To enhance the performances of bored pile concrete in permafrost regions, this study explored the influence mechanism of 1,2-PPD on the mortar performances subjected to the negative temperature curing condition. The results indicate that the addition of 1,2-PPD improves the compressive strength of the mortar samples at 7, 14, 21 and 28 days of curing, and the optimal content of 1,2PPD is 0.5 %. Through the analysis of the results obtained from the thermogravimetric test and the hydration heat test using the dissolution heat method, it is determined that 0.5 % 1,2-PPD maximizes the hydration degree of cement, leading to increased production of hydration products and the denser pore structure in the mortar samples. After 28 days of curing, the mortar sample demonstrates the highest compressive strength, exhibiting the remarkable increase of 60.6 %. Additionally, the mortar sample presents the smallest rapid chloride ion migration coefficient and the optimal pore characteristics.