Study On Properties Of Modified Recycled Aggregate Waterpermeable Concrete Based On Core-shell Structure

In the process of using recycled aggregates to prepare concrete,recycled bricks have always become a weak link that affects the performance of concrete.How to turn waste into treasure and give full play to the advantages of recycled bricks is currently a difficult problem in realizing the utilization of construction waste.This research has a unique approach.By modifying the recycled bricks,it can not only improve the mechanical properties of the aggregate,but also give it the characteristics of water storage and release.It can be used to prepare permeable water storage concrete,which can realize the resource utilization of construction waste.It can also solve the key material problems urgently needed for the construction of sponge cities and green ecological urban areas.This study explored the water storage and release principles of porous media,the effect of the cladding layer on the water storage and release properties of recycled aggregates,and the modification of recycled brick aggregates.The change law of macroscopic properties of permeable water storage concrete based on multiple factors is studied.The research on the influence mechanism of modified recycled aggregate replacement rate on the frost resistance of permeable water storage concrete was completed.The main research conclusions are as follows:(1)Based on the transmission mechanism of moisture in concrete.The transmission mechanism of water in unsaturated concrete is used to analyze the water storage and release process.The control equation of the water storage and release mechanism is: /-▽(()▽ )= 0.This study proposes to use water absorption during water storage to characterize water storage performance;the slope of the fitting curve in the 0.2h～1.8h section during water release is used as a new idea to evaluate the diffusion coefficient,which is used to characterize the water content in aggregate The water release rate has laid the foundation for a correct understanding and analysis of the mechanism of water storage and release.(2)Study the effect of modified recycled aggregate core-shell structure on the water storage and release performance of modified recycled aggregate.It was found that the thickness of the shell is 1～2.5mm and the water-cement ratio is in the range of 0.3～0.5.The modified recycled aggregate has good water storage and release properties.Cement paste was used to modify the bricks,and the rationality of the modification method was evaluated based on the 24 h water absorption rate and cylinder pressure strength.It was found that the two indicators were better when the secondary dry mixing method was used for modification.(3)Based on the mix ratio design of the absolute volume method,by changing the watercement ratio,ash set ratio and compaction degree to study its impact on the performance of permeable water storage concrete,a large number of system tests show that: when the watercement ratio is 0.28,the ash set When the ratio is 0.56 and the degree of compaction is 0.94,the mechanical properties and comprehensive performance of permeable water storage concrete are excellent.(4)The effects of modified recycled aggregate replacement rate and aggregate particle size on the performance of permeable water storage concrete were studied respectively: When the particle size of modified recycled aggregate is in the range of 9.5～16mm,the mechanics and storage release of permeable water storage concrete The best water performance;compared with recycled bricks and natural crushed stone,modified recycled aggregate can improve the water storage and release performance of permeable concrete,and at the same time,the mechanical properties of concrete have been improved to a certain extent,solving the problem of difficult application of recycled aggregate At the same time,it also gives concrete a certain water storage and release performance.(5)The antifreeze test shows that as the amount of modified regenerated aggregate increases,the strength and mass loss rate after 50 freeze-thaw cycles increase;as the amount of mineral powder increases,the strength and mass loss after 50 freeze-thaw cycles are both Reduce,when the amount of mineral powder is 20%,the strength and quality loss are minimal.Studies have shown that by optimizing the mix ratio of modified recycled aggregate concrete and incorporating mineral powder,the frost resistance of this type of concrete can be effectively improved,and it has good application prospects.