Polycarboxylate-based water reducing admixture - clay compatibility; literature review

Abstract

Polycarboxylate-based water reducing admixtures (PCE) are widely used in concrete technology as they have superior properties such as ease of molecular structure change, high dispersing and water reduction capacity. Besides these positive effects, PCEs show a high sensitivity to clay particles. Surface adsorption and intercalation of PCEs with clays reduce their dispersing and water reduction capacity. The action-performance of PCE depends on the morphological properties of clays and the chemical structure of PCEs. Approaches such as increasing PCE dosage, adding polyethylene-glycol (PEG)-grafted lignin, and using clay tolerant sacrificial agents were proposed to avoid the adverse effect of clays on the action performance of PCE. However, as these approaches are not economical, there is a need to synthesize modified PCEs. In this study, PCE-clay interaction and methods to increase the action-performance of PCE in systems containing clay were investigated in detail. It was reported that the addition of functional groups to PCEs or use of PCEs with short polyethylene oxide (PEO) side chain lengths limit intercalation. In addition, it was emphasized that the size of the side chain shape that the clays cannot be included in the interlayer region prevents intercalation and increases the action-performance of PCE.