Abstract
•Cementitious Paste Volume (CPV) and Wet Packing Density (WPD) are critical factors affecting concrete shrinkage.•Replacing partial cement with fly ash (FA) or limestone (LS) can decrease shrinkage of concrete.•Shrinkage of concrete containing FA or LS could not be well predicted by AS3600 shrinkage model.•A proposed shrinkage equation can predict more satisfactorily the concrete shrinkage by considering CPV and WPD.
Shrinkage of concrete needs to be dealt with carefully in the design of reinforced concrete (RC) structures as it creates dimensional instability and could induce excessive tensile stress in restrained member that impacts durability. To mitigate concrete shrinkage, the critical factors such as water-to-cementitious material (W/CM) ratio, dosage of superplasticizer (SP), concrete strength and cementitious paste volume (CPV) needs to be considered in the concrete design mix. While the effects of concrete strength on shrinkage are straightforward, those of CPV, W/CM and SP are more complicated because they also affect the pore size and distribution that influence the moisture movement. In a previous study, the authors proposed to use wet packing density (WPD), which can relate the volume of voids in fresh concrete to the capillary pores in hardened concrete, to account for the combined effect of W/CM and SP on concrete shrinkage. It was proven that the shrinkage of concrete can be correlated negatively to the WPD and positively to CPV. In this paper, the shrinkage test results obtained in the authors’ previous test is converted into a shrinkage design model taking into account the effect of CPV and WPD for real application in concrete mix design. The model can better predict the shrinkage of concrete at different ages up to 91 days than that in the Australian Code AS3600.