Effect of side chain length change of polycarboxylate-ether based high range water reducing admixture on properties of self-compacting concrete

Abstract

In this study, the effect of side chain length, molecular weights changes and adsorption amount of polycarboxylate ether-based high range water reducing admixtures having constant main chain length, free non-ionic amount and anionic/non-ionic ratio on fresh properties, early and advanced age compressive strength, water absorption capacity and ultrasonic pulse velocity value of self-compacting concretes (SCC) were investigated. FTIR (Fourier transform infrared) and GPC (Gel Permeation Chromatography) analyzes were carried out to characterize admixtures. According to the test results, all SCC mixtures produced within the scope of the study provided EFNARC criteria. If the admixture side chain length is higher or shorter than a certain value, the admixture requirement is increased for providing the desired target slump-flow value in SCC mixtures. This negative effect is thought to be due to the weakness of the steric hindrance effect for admixture with short side chain, the low adsorption amount and interlacing risk of side chains for admixture with the long side chain. On the other hand, the increase in the side chain length of the admixtures had a positive effect on the time-dependent fresh state performance of the mixtures. This positive effect is thought to be due to the low adsorption amount of the admixture, the increase in the side chain length and the increase of the non-adsorbed free polymer content in the mixture. While side chain length change of the water reducing admixture affected the 1 and 2-day compressive strength values of SCC mixtures, the 3, 7 and 28-day compressive strengths and the 28-day water absorption, ultrasound and dynamic elasticity modulus values did not significantly affect.