Study On Properties Of Wrapped Slurry Recycled Concrete

In order to cope with the increasing shortage of aggregate resources and the increasing pressure of waste concrete,recycled concrete is an inevitable choice for the sustainable development of concrete materials.However,the quality of recycled aggregates with low intensity and brittleness is seriously restricting the development of recycled concrete.How to improve the skeleton rigidity of recycled aggregates is an important and difficult subject in current concrete research.In this paper,we try to overcome the performance defects of recycled aggregate by applying pre-sizing method to recycled aggregate,and find a technical way to prepare wrapped slurry recycled aggregates with good shape,good mechanical properties and potential volcanic ash effect in the surface.Based on the optimization of the composition of the wrapped slurry and the wrap method,comparison and optimization of the wrapp age,experiment was carried out to study how sphericity coefficient,physical and mechanical properties of wrapped slurry recycled aggregates affect the mechanical performance and durability of wrapped slurry recycled concrete,and the volcanic ash effect and the secondary hydration mechanism of the transition zone between the slurry and the cementite interface are clarified by microstructure study,which opens up new directions and new ways for the development of recycled aggregate.(1)Through the treatment of recycled aggregates with slurry,it can improve the grain shape and gradation of recycled aggregates,eliminate the microcracks on the surface of recycled aggregates,optimize the particle size distribution of recycled aggregates,reduce needle tablets-like content of the aggregate,and significantly improve the crushing index of recycled aggregates,but the iMPact on the water absorption is weak.In general,the overall performance of the aggregate can be improved by wrapped slurrying recycled aggregates.(2)Through the treatment,we can not absolutely improve the strength of concrete,but the toughness of concrete can be improved.Optimum strength of concrete could be get when recycled aggregates wrapped slurry for 3 days,which could meet the intended test objectives.The influence of the toughness of concrete is not very significant due to the influence on the strength of the wrapped slurry aggregate itself.(3)The shrinkage tendency of wrapped slurry recycled aggregates concrete is similar to that of ordinary concrete,but the early shrinkage of the concrete changes more slowly.With the increase of aggregate wrapped slurry age,the shrinkage rate of the concrete is increasing,and the trend is steep at first and then goes slow.The shrinkage change is relatively large in 60 days,especially in 7 days and the concrete shrinkage shows an exponential growth trend.The frost resistance of wrapped slurry recycled aggregates concrete can be improved with the use of wrapped slurry recycled aggregates,and the frost resistance of concrete is the best when the aggregate is wrapped slurry for 28 days.(4)Through the comprehensive analysis,the optimal group of wrapped slurry recycled aggregate was selected as Y3 group,and it was confirmed by experiment.The slurry was prepared by using water-cement ratio of 0.35 and 2%of powdery powder on the recycled aggregate.After 3 days of curing,wrapped slurry recycled aggregate concrete with the best overall performance was produced.