Influence Of Nano-silica Soaked Recycled Aggregates On Properties Of Concrete

With the development of construction industry in our country,a lot of sand and gravel resources being used.At the same time,the production of construction waste in increasing year by year,the result is the shortage of natural sand resources and a large number of construction waste pollution to the environment.Construction waste is mainly composed of waste concrete,using waste concrete as recycled aggregates is applied to the building is an important way to solve the problem.But because of recycled aggregates has high crushing index,water absorption was high and the characteristics of low apparent density leads to the production of recycled aggregate concrete quality is low.So to develop a efficient method to improve the performance of the recycled aggregates is particularly important.In this paper,Modification of the recycled aggregates by nano-SiO₂ to comparing before and after the modification of recycled aggregates crush index,water absorption and the apparent density.To establish the nano-SiO₂ best conditions for modification of recycled aggregates.The modification mechanism of nano-SiO₂ on recycled aggregate was studied by microcosmic experiment.The effect of nano-SiO₂ on the performance of recycled aggregate concrete was studied by using the recycled aggregate before and after modification.The results are as follows:?Physical properties test of recycled aggregate:With 3%nano-SiO₂ treatment the recycled aggregate RAI,RAII and 2.25%concentration of nano SiO₂ treatment the recycled aggregate RAIII and RAIV,and the crushing index,water absorption and apparent density had the most obvious improvement effect.And the improvement effect of vacuum mode is better than that normal pressure way?The microsmic experiments of the recycled aggregate showed:That the number of gel hole??50nm?in the modified regenerated aggregate was increased,and the number of large holes?>50nm?decreased.The content of Ca?OH?₂ in the modified recycled aggregate was reduced obviously.The microscopic image before and after modification shows that the internal structure of the modified recycled aggregate is denser.?The test of recycled aggregate concrete shows:Nano-SiO₂ decreased the fluidit y of recycled aggregate concrete;modified than before modification of recycled aggregate concrete strength increases in 8.6%²0.1%.Recycled aggregate sources under the same condit ions of nano SiO₂ improve the concrete strength of C30 group better than C50group;C30 group for the modification of recycled aggregate concrete before and after can reach the design strength.But the C50 group using powder and silica sol modified optimal group to meet the design strength of 94%and 93%respectively.The microscopic images indicate that modification of recycled aggregate concrete interfacial transition zone was more compact than the modified before.In conclusion,the use of nano SiO₂ modified recycled aggregate not only improve the quality of recycled aggregate,but also improve the performance of recycled aggregate concrete,which helps to improve the research process of recycled aggregate quality.