New insights in the adsorption behavior of triethanolamine on OPC by experimental and theoretical study

Abstract

The influence of triethanolamine (TEA) on the hydration of cement-based materials is closely linked to its adsorption behavior in Ordinary Portland Cement (OPC). This study investigated the adsorption process and mechanism of TEA on OPC and pure mineral phases—alite, gypsum, aluminate+gypsum, and calcium hydroxide (CH)—in the first 8 h. The results revealed that in all single phases, TEA adsorption was associated with alite and CH. The crystal structure of CH did not change during adsorption, likely due to the physical adsorption of TEA. During OPC hydration, the adsorption of TEA was primarily associated with the hydration of alite. In the initial hydration stage, only CH served as the main adsorption receptor, which was supported by adsorption energy simulations using molecular dynamics. As alite hydration progresses, the role of the receptor may shift toward calcium silicate hydrate (C-S-H), as indicated by the calculated adsorption limit of CH. Furthermore, density functional theory (DFT) demonstrated that TEACa²⁺ has the lowest complexation energy when the ligand-to-metal ratio is 1:1 and becomes even more stable when the ligand-to-metal ratio is 2:1.