Influence of water to cement ratio on the compatibility of polycarboxylate superplasticizer with Portland cement. (25th July 2022)

• Record Type: Journal Article
• Authors: Lu, Zichen; Lu, Jiayun; Liu, Zhiwei; Sun, Zhenping; Stephan, Dietmar
• Is Part Of: Construction & building materials. Volume 341(2022)
• Publication Date: 2022-07-25
• Subjects: Compatibility -- Cement -- Polycarboxylate superplasticizer -- Water to cement ratio -- Mechanism; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2022.127846
• Languages: English
• ISSNs: 0950-0618

Abstract

Graphical abstract: Highlights: A low w/c ratio can trigger the incompatibility of PCE with cement. PCE with a higher charge density leads to a faster stiffening of cement paste. Incompatibility is directly caused by the fast hydration of aluminate phase. The different C3 A polymorphs could be an important reason for the incompatibility. Abstract: The effect of water to cement (w/c) ratio on the compatibility of polycarboxylate superplasticizer (PCE) with ordinary Portland cement was investigated through multiple experiments, including mini-slump flow, ultrasonic pulse velocity, setting time, calorimetry and pore solution analysis. The incompatibility of PCE with cement can be found under a low w/c ratio of 0.27 and the increased w/c ratio can eliminate the incompatibility. Besides, the PCE with higher charge density shows more serious incompatible issue. Further analysis proves the incompatibility is caused by the rapid precipitation of monosulfate and ettringite. The mechanism analysis indicates that the incompatibility is not caused by hindered dissolution of sulfate carriers, but the accelerated dissolution of orth C3 A, through which the chemistry of bulk solution is significantly modified. The increased w/c ratio can alleviate the effect of orth C3 A dissolution on the chemistry of bulk solution and make the performance back to normal.