Effect of TEA·H3PO4 and TEA·C18H30O3S on the mechanical properties and hydration characteristics of cement paste. (3rd January 2022)

• Record Type: Journal Article
• Authors: Zhao, Yazhou; Zhu, Zhenyu; Chen, Yang; Li, Shagang; Zhao, Yue; Li, Xiaoyu; Wu, Min; Chen, Da
• Is Part Of: Construction & building materials. Volume 314:Part B(2022)
• Publication Date: 2022-01-03
• Subjects: Accelerator -- TEA·H3PO4 -- TEA·C18H30O3S -- Hydration heat evolution -- Portlandite; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2021.125635
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Two types of chloride-free accelerators were systematically investigated. Less than 0.10% TP and 0.05% TDS shorten the initial setting time. TP decreases the generation of CH but TDS facilitates the generation of CH. Air-entraining effect of TDS leads to the decline in mechanical properties. Strength enhancement of mortar with TP is related to CH size. Abstract: In this study, TEA·H3 PO4 (TP) and TEA·C18 H30 O3 S (TDS) have been used as organic admixtures in cementitious materials. Mortar specimens with different TP and TDS dosages were subjected to mechanical, setting time, hydration degree, isothermal calorimeter tests, as well as to XRD, TG, SEM and MIP analyses. Results show that less than 0.10% TP and 0.05% TDS shorten the initial setting time, while more than 0.50% TDS can lead to a retarding effect in mortar specimens. TP is beneficial to increase the early age strength, but a sharp decrease in both compressive and flexural strengths is found when TDS is introduced. The XRD and TG analyses indicate that the introduction of TDS brings more generation of the portlandite (CH), ettringite (AFt), and monosulfate (AFm), whereas TP leads to the reduction of CH content in the cement pastes. Moreover, the SEM observations reveal that the decline in strength may result from the air-entraining effect caused by the incorporation of TDS which increase the amount and size of hydration pores, and the variation of mechanical properties of mortar specimens with TP is closely linked to the size of CH generated in mortar specimens.