Effect of diethanolisopropanolamine and ethyldiisopropylamine on hydration and strength development of Portland cement

Abstract

Diethanolisopropanolamine (DEIPA) and ethyldiisopropylamine (EDIPA) are new types of alkanolamines, which can be used in grinding aids or accelerators. Effect of DEIPA and EDIPA at different dosages (0.05 % and 0.5 %) on cement hydration and strength development is studied by compressive strength, heat evolution, X-ray diffraction (XRD), thermogravimetry (TG), 1H nuclear magnetic resonance (1H NMR) and scanning electron microscope (SEM). Results indicate that both dosages (0.05 %, 0.5 %) of DEIPA or EDIPA accelerated the hydration of aluminate (C3A), ferrite (C4AF), alite (C3S) and belite (C2S) due to their complexation effect. The main hydration peak was advanced and enhanced by 0.05 % of DEIPA or EDIPA, while it was significantly weakened with 0.5 % of DEIPA or EDIPA incorporation due to the large formation of calcium monosulfoaluminate hydrate (AFm). Compared with DEIPA, EDIPA under both dosages caused more AFm formation and led to lower hydration degree of C3S and C2S at early ages, and possessed higher air entraining property to cause pore structure degradation. However, EDIPA contributed to higher hydration degree of C3S and C2S at later ages due to its higher steric hindrance than DEIPA. As a result, cement mortars with 0.05 % of DEIPA or EDIPA present higher or comparable compressive strength compared to the reference sample, with DEIPA005 primarily increased the early strength while EDIPA005 mainly increased the later strength. Whereas, DEIPA or EDIPA at higher dosage (0.5 %) considerably decreased early strength of cement mortars, especially EDIPA.