Rheology and Air Void Structure of Fresh Concrete under Vibration

Abstract

Abstract: Vibration is an essential mean of concrete compaction and forming. The effect of vibration directly determines the mechanical properties and durability of hardened concrete. Based on Stokes' law, this paper proposed a new method for measuring and evaluating the rheology of fresh concrete under vibration, namely, the pulling-ball method. The correlation between the rheological parameters obtained by this method and those obtained by the rheometer at static state was analyzed, demonstrating the pulling-ball method's reliability for evaluating the rheology of fresh concrete. The results show good linear correlations between the plastic viscosity and the yield stress obtained by the pulling-ball method and those obtained by the rheometer individually. Vibration can reduce the viscous drag force of cement mortar near the internal poker vibrator by more than 90% and effectively discharge large bubbles (pore size Φ>500 μm) and retain tiny bubbles (Φ<200 μm). Vibration substantially affects removing large bubbles with increasing air-entrained agent (AEA) content. When the AEA content roses from 0.015% to 0.030% (mass fraction), the decreasing of air void content with the pore size of [500,1 000) μm increases from 31.0% to 84.8%, and those with the pore size of [1 000,2 000) μm increases from 10.3% to 36.4%.

Key words: fresh concrete, vibration, rheology, air void structure, evaluating method, air-entrained agent

CLC Number:

TU528

JIN Yang, PAN Junzheng, ZHONG Liang, HAN Yongshu, ZHOU Guangzhao, GAO Xiaojian. Rheology and Air Void Structure of Fresh Concrete under Vibration[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(11): 3866-3877.

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