Influence of adding fly ash and mineral powder on mechanical properties of coarse aggregate total replacement concrete
In order to study the influence of mineral powder and fly ash on the mechanical properties of C30 coarse aggregate fully replaced recycled concrete,14 groups of specimens were prepared,including single fly ash and mineral powder with substitution rates of 0,5%,10%,15%,20%and double fly ash plus mineral powder:5%+5%,5%+10%,10%+5%,10%+10%,15%+15%.Their slump,compressive strength,splitting tensile strength and compressive deformation were measured and analyzed by scanning electron microscope.The results show that the workability of recycled concrete can be effectively improved when the content of fly ash is less than 20%and the content of mineral powder is less than 10%.The slump increases first and then decreases when the content of fly ash is 10%and the content of mineral powder is 5%,and the maximum slump is 190 mm.The strength requirements of C30 concrete can be met under the conditions of single admixture and double admixture.When single admixture is used,20%admixture can be considered.When double admixture is used,10%fly ash and 5%mineral powder can be considered to replace cement in terms of workability and strength.The deformation of single fly ash is less than that of the foundation group.The deformation of single fly ash is nearly twice that of the foundation group.The deformation of double fly ash is much larger than that of the foundation group.The observation of the microstructure of recycled concrete confirmed the macroscopic measured data and the cause analysis of the compressive strength of the test block.
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