Effect of fine aggregate type on early-age performance, cracking analysis and engineering applications of C50 concrete

Due to the increasing resource shortage and environmental problems caused by the over-mining of river sand, manufactured sand has been adopted as an alternative to river sand as an important component of modern concrete in some engineering construction processes. However, the uncertain stone dust content of manufactured sand has the potential to cause a reduction in the crack resistance of concrete, especially in practical engineering applications. This paper compares and analyses the effect of river sand and manufactured sand on the basic properties of C50 concrete and explores the law of fine aggregate type on the cracking resistance of concrete. The results of the study show that the tensile strength of manufactured sand concrete (MSC) is not as good as that of river sand concrete (RSC) in the case of large amounts of fly ash and slag, and the working properties of both are relatively close. The effect of different fine aggregate types on the adiabatic temperature rise of concrete is not significant and remains largely consistent. However, in the engineering application of large volume thick base slab concrete, the internal generation of heat of hydration is greater, the temperature rise is higher and the difference between internal and external temperature and cooling shrinkage is prone to the risk of temperature cracks due to temperature stresses. Therefore, with a small difference in adiabatic temperature rise between RSC and MSC, the magnitude of temperature stresses generated is close, but since the use of manufactured sand leads to a decrease in the tensile strength of the concrete itself, the risk of cracking is greater in MSC compared to RSC. Finally, the RSC mix proportion obtained from the laboratory were successfully applied to the foundation slab of a 500 m tall building, which is of great practical engineering importance.