A comparative investigation of hydration reaction of Portland cement with the use of alkanolamine as a chemical admixture or grinding agent under laboratory condition

Abstract

Although alkanolamine (AA) have been utilized in cement production for ages, its chemical impact on cement hydration has not been well understood. To elucidate the underlying mechanism, a comparative study was conducted using AA, including ethanol diisopropanolamine and diethanol isopropanolamine, either as a grinding agent (GA) or as a chemical admixture (CA). When AA was added as a CA, delayed tricalcium silicate (C3S) reaction was observed. Meanwhile, added AA during grinding enhanced C3S reaction both in the early and later stages. In both stages, the hydration of tetracalcium aluminoferrite was also enhanced, leading to the decomposition of the AFt phase into hemicarboaluminate and monosulfoaluminate phases. However, these effects were less activated in CA samples, resulting in lower production of C–S–H and AFm phases as well as reduced strength. It is suggested that the favorable hydration effect of GA can be significantly underestimated when it is tested as a form of CA.