Influence of Super Early Strength Polycarboxylate Superplasticizer on Time-dependent Behavior of Rheological Properties and Air-Void Structure of Low Slump Concrete
JIANG Qian1, YU Cheng1, YUAN Sensen1, RAN Qianping2
1 State Key Laboratory of High Performance Civil Engineering Materials, Jiangsu Sobute New Materials Co. Ltd., Nanjing 211103, China 2 School of Materials Science and Engineering, Southeast University, Nanjing 211189, China
Abstract: Polycarboxylate (PCE) comb-like copolymers with super-length side chains (i.e., one with ether-type side chains and the other with ester-type side chains) and normal-length side chains were employed to prepare low slump concrete in this paper. Influence of the superplasticizers on the time-dependent behavior of fresh properties and air-void structure of low slump concrete were investigated by fluidity test, rheological analysis, air-void parameters measurement of wet-screened mortar and air bubble shape 3D reconstruction in the mortar during hardening. The results showed that a strong linear relationship between fluidity and yield stress of the wet-screened mortar as Bingham fluid was revealed, regardless of PCE types. Superplasticizers with super-length of side chains weakened the fluidity retention of mortar in comparison with superplasticizer of normal molecular structure. The two PCEs with super-length side chains presented less initial air-entraining efficacy and amount ratio of small air bubbles than the normal one, and advanced the process of reduction of small air bubbles and growth of large air bubbles. The 3D reconstruction analysis of air bubble shape visually proved the coalescence of adjacent bubbles exists, and PCEs with super-length side chains led to an earlier coalescence.
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