Multi-scale creep analysis of river sand and manufactured sand concrete considering the influence of ITZ

Abstract

This paper investigated the multi-scale prediction of long-term creep in river sand (RS) concrete and manufactured sand (MS) concrete and analyzed the effect of the interfacial transition zone (ITZ) around the aggregate on the creep properties of concrete. Uniaxial compressive creep tests were conducted on the concrete for a duration of 360 d. The creep kinetic properties of the paste matrix and ITZ were obtained by microindentation test. The properties of ITZ were determined by the backscattered electron (BSE) image threshold segmentation technique and the Lu & Torquato model. Finally, the predicted concrete creep modulus was obtained through the calculation of creep homogenization, and the accuracy of multi-scale creep prediction when considering different ITZ cases was discussed. The results show that under the same water-binder ratio, the thickness of ITZ around MS was larger, the creep modulus was smaller and the volume fraction was larger compared with that of ITZ around RS. In the multi-scale homogenization calculation of the concrete long-term creep, the prediction accuracy of the computational model increased with the raised of the considered ITZ types. The prediction accuracy obtained when all ITZs were considered was improved by more than 46.3% compared to that when no ITZs were considered.