Experimental study and prediction of the long-term strength development of high-flowability concrete made of mixed sand and high-content fly ash
Minglei Zhao, Jie Li, Changyong Li, Jianhu Shen
Abstract
To comprehensively utilize the abundant solid wastes of superfine river sand and fly ash, a mixed sand of superfine river sand with coarse manufactured sand and high-flowability concrete made of mixed sand and high-content fly ash were developed. To address the critical question about the long-term strength of this new concrete, this paper presents an experimental study on the long-term development of cubic compressive and tensile strengths of the concrete over a curing age from 7 days to 360 days. In the study, the mixed sand was a hybrid of 40 % superfine river sand and 60 % coarse manufactured sand, and the fly ash content varied from 30 % to 75 % of the total binders by weight. The law of strength development of concrete with fly ash content was analyzed, combined with explanations of the mechanism and observations of hydration exotherms and microstructures of the concrete. Equations were proposed for predicting the long-term development of cubic compressive and tensile strengths, incorporating coefficients to reflect the effects of fly ash on the binder’s compressive strength and the development tendency of concrete strength. The validity of the proposed prediction equations was verified against the test results and compared with the extended application of the equation specified in CEB-FIP MC 2010. • Mixed sand of superfine river sand with coarse manufactured sand was developed. • High-flowability concrete made of mixed sand and high-content fly ash was produced. • Long-term strength of the concrete was measured within the curing age of 360 days. • Formulas for predicting strength development were proposed. • Coefficients reflecting the effect of fly ash on strength development were suggested.