Effect of fly ash on mechanical properties and pore structure of high-strength concrete
To investigate the impact of fly ash replacement cement ratios on the strength and internal pore structure changes of manufactured sand high-strength concrete(MSC)and natural sand high-strength concrete(NSC),C80 high-strength concrete was designed with fly ash replacement cement ratios of 0,10%,15%,20%,and 25%,respectively.Nuclear magnetic resonance(NMR)technology was used to analyze the evolution of concrete pores,and X-ray diffraction(XRD),diffe-rential thermal gravimetric analysis(DTA),as well as field emission scanning electron microscopy(SEM)technology were used to analyze the morphology and microstructure of hydration products in ce-mentitious materials.The results show that the strength of MSC is higher than that of NSC at all ages,and the initial strength decreases with the increase of fly ash content.In the later stage,the strength of 10%fly ash concrete is the highest;10%fly ash promotes the hydration process of cement and fills gel pores to reduce the generation of cracks,thus optimizing the internal structural pores of concrete and improving the overall compactness of concrete.Considering the influence of fine aggregate morphology parameters and fly ash substitution rate on concrete strength,a 28-day compressive strength prediction model for fly ash concrete is established based on the compressible stacking theory with good accuracy.The research can provide some reference for the high-quality application of fly ash high-strength concrete.
fly ashmanufactured sandhigh-strength concretenuclear magnetic resonancecompressible packing theory
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