Effect of Alkanolamines on the Early-Age Strength and Drying Shrinkage of Internal Curing of Mortars

Abstract

In this study, the reduction of the early-age strength of mortar caused by the traditional super absorbent polymer (SAP) was solved. Two types of alkanolamines (Alkanolamine-A and alkanolamine-B) and calcium nitrite were compounded with traditional SAP as early-age strength components and then were added into the mortar to evaluate effects on early-age strength and drying shrinkage. Results showed that adding two types of alkanolamines could significantly improve the early-age compressive strength of mortar. The addition of alkanolamines could refine the pore of cement paste and reduce the average pore size, which can be reflected by the increased strength and improved mortar drying shrinkage. Among them, the mortar with the composite of alkanolamine-A and alkanolamine-B added showed excellent performance. Its mechanical properties increased to 129% at day 3 and 139% at day 7 compared with the reference group; compressive strength can reach up to 31.8 MPa. The average pore size of the cement paste decreased by 27.8%, and the drying shrinkage was significantly smaller compared with the reference group.