Differences between their influences of TEA and TEA·HCl on the properties of cement paste

Abstract

It is still uncertain whether there are some differences between their influences of TEA and TEA·HCl on the properties of cement paste. Thus, this work aimed to evaluate the differences between their influences of TEA and TEA·HCl on the properties of cement paste. Then the cement pastes or mortars with 0%, 0.01%, 0.015%, 0.02%, 0.06%, 0.10%, 0.20%, 0.50% and 1.00% TEA and TEA·HCl respectively were prepared and their setting times and compressive strengths were investigated. Meanwhile, the chemical shrinkage, pore size distributions, hydration heat releases, thermogravimetric (TG) characteristics and microstructures of vaious pastes were studied to explore the mechanisms that are responsible for these differences. The results show that less than 0.2% TEA·HCl reduces the initial setting time more significantly, whereas 0.02%, 0.06% and 0.1% TEA·HCl are inclined to shorten the finial setting time as comparing with the same content of TEA. Less than 0.1%, 0.02% and moderate TEA·HCl more significantly enhance the compressive strengths at 3 d, 7 d and 28 d respectively in comparison to the same content of TEA. These pastes with less than 0.2% TEA·HCl have the greater chemical shrinkage at 24 and 72 h, the cement pastes with less than 0.02% TEA·HCl provide the greater rate of hydration liberation in the initial fast reaction period, these pastes with 0.2% TEA·HCl display the more significantly increaseed rate of hydration heat liberation in the acceleration period as well as the more total hydration heat liberation at 72 h, as comparing with the cement pastes with same content of TEA. Besides, TG result indicates that these hardened pastes with TEA·HCl form the more CH at 3 d, whereas these hardened pastes with less than 0.06% TEA have the more CH at 28 d. These hardened pastes with 1%, 0.2% and 0.5% TEA·HCl have the relatively less pore voume as compared with the pastes with same contents of TEA at 28 d. The result of the scanning electron microscope (SEM) image shows that in the presence of same content of TEA and TEA·HCl, TEA·HCl is more liable to alter AFt and CH morphology. These discriminative results in the chemical shrinkage, pore sizes distribution, hydration heat release, TG and SEM provide an envience for the differences between their influences of TEA and TEA·HCl on the properties of cement paste. These results will provide a reference for the selective use of TEA and TEA·HCl as an accelerator.