Effect of the polycarboxylate based water reducing admixture structure on self-compacting concrete properties: Main chain length

In this study, the effect of polycarboxylate ether-based water reducing admixture (WRA) main chain length on fresh state properties, compressive strength, ultrasonic pulse velocity (UPV) and water absorption capacity of self-compacting concrete (SCC) mixtures were investigated. Within this aim, three polycarboxylate ether-based high range WRAs with stabilized polyethylene oxide side chain molecular weight, free non-ionic content and constant anionic/non-ionic ratios, but different main chain length were synthesized. FTIR (Fourier transform infrared) and GPC (Gel Permeation Chromatography) analyzes were carried out to characterize admixtures. According to test results, the admixture requirement for reaching targeted main chain length in SCC increased and adsorption of admixture decreased in case the admixture main chain length is higher and lower than a certain value. However, time-dependent flow performance of the mixtures improved with the increase of admixture main chain length and a reverse situation was observed when the length was decreased. Similar behaviors were also observed in V funnel flow, L box and U box passing tests. While the admixture main chain length change affected early age strength, it showed no effect on the strengths of later ages. No considerable differences were observed in the 28-day water absorption, UPV and dynamic modulus of elasticity values of the mixtures with the change of admixture main chain length. (C) 2020 Elsevier Ltd. All rights reserved.