Relations of Compressive Strength at 7d and 28d for Fly Ash Concrete with Machine-Made Sand

Although the fly ash concrete with machine-made sand (MSFAC) was widely used in recent years in China, it was lack of studies on relations of compressive strength at different ages. According to the specification of Chinese standard, there are three ways of admixing fly ash (FA) into concrete, i.e. the additional admixing, the equal-mass replacing cement and the over-mass replacing cement. In this paper, 56 groups test data with additional admixing FA, 98 groups test data with equal-mass replacing cement and 86 groups test data with over-mass replacing cement for MSFAC are summarized from published references. Three linear formulas and Slatter formulas are fitted and compared for MSFAC by the different methods of admixing FA, all of them have good fitness with test data. The compressive strength at 28d can be predicted by the compressive strength at 7d with linear formula and Slatter formula for MSFAC.