Effect of triethanolamine hydrochloride on the performance of cement paste.

Highlights • Moderate TEA·HCl decreases the water requirement. • It also shortens the setting times and alters strengths. • It delays the end time of the induction period. • Excessive TEA·HCl accelerates AFt conversion to AFm. Abstract Triethanolamine (C 6 H 15 NO 3 , TEA) is one of the known organic amine accelerators for the cement-based materials. Triethanolamine hydrochloride (C 6 H 15 NO 3 ·HCl, TEA·HCl), part of whose molecular structure is the same as TEA, can also be regarded as chloride. Thus the water requirement for the normal consistency, setting time, strength, hydration heat liberation, calcium hydroxide (CH) and ettringite (AFt) contents in the hardened paste with TEA·HCl were analyzed and the effect of TEA·HCl on the performance of cement paste was studied to assess the feasibility of TEA·HCl used as an identical accelerator. The results indicate that moderate TEA·HCl decreases the water requirement for the normal consistency and this decline is related to the formation of the absorbed film on the cement particle. Zeta electric potential result also proves the appearance of the absorbed film. It also shortens the setting times and alters strengths. But the alterations of setting times and strengths depend on the TEA·HCl content. Heat liberation result implies that it delays the end time of the induction period and also postpones tricalcium silicate (3CaO·SiO 2 , C 3 S) hydration at early age, however moderate TEA·HCl increases the rate of C 3 S hydration in accelerated phase. Excessive TEA·HCl accelerates the AFt conversion to monosulfoaluminate (AFm) after several hours. The conversion product is the AFm with 14 H 2 O. TEA·HCl changes the total heat liberation, and these pastes with more TEA·HCl liberate more heat before about 12 h, but this case is reverse after about 12 h. X-ray powder diffraction (XRD) and differential thermal analysis (DTA) results conformably confirm that excessive TEA·HCl delays C 3 S hydration and decreases CH content in the hardened paste, but it increases the AFt content in the hardened paste. Hardened pastes with TEA·HCl provide the higher content of AFt than the control even at 28d. Heat liberation, CH and AFt contents are closely responsible for the results of the setting times and strengths. These results will provide a reference for the TEA·HCl application as an accelerator in the practice. [ABSTRACT FROM AUTHOR]