Effect of recycled fine aggregate on mechanical properties and autogenous shrinkage of ultra-high performance concrete
The application of recycled fine aggregate to ultra-high performance concrete(UHPC)not only reduces its cost,but also realizes the resource utilization of construction waste.UHPC was prepared by pre-wet recycled fine aggregate(RFA).The effects of particle sizes(0.6～＜1.18 mm and 1.18～2.36 mm)and replacement rates(10%,20%,30%and 40%of volume fraction)of pre-wetted treatment RFA on working performance,mechanical properties,volume stability and chlo-ride ion penetration resistance of UHPC were investigated.The mechanism was revealed by microhardness,TG-DTG,MIP and SEM.The results showed that the particle size and content of recycled fine aggregate were the key factors that deter-mined the workability,mechanical properties and shrinkage properties of UHPC.With the increase of RFA content,the flu-idity and autougenous shrinking of UHPC were decreased gradually.But its compressive strength showed a trend of increas-ing firstly and then decreasing,among which UHPC prepared with 20%pre-wetted recycled fine aggregate(particle size of 1.18～2.36 mm)showed better performance.Compared with the control group,the 28 days compressive strength was in-creased by 7.0%,while the autougenous shrinking was decreased by 78.8%.The pre-wetted RFA released water into the UHPC matrix,reduced the internal self-drying process,and improved the degree of hydration reaction,which optimized the interface composition structure,and thus refined the internal pores of the matrix.
ultra-high performance concreterecycled fine aggregatemechanical propertiesautougenous shrinkagepore structure
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