Research On The Basic Properties Of Wrapped Slurry Recycled Aggregates And The Granularity Optimization Effect

Construction waste has distinctive temporal,spatial and persistent hazards.Reusing construction waste not only solves the scarcity of resources,but also reduces the burden on the environment.Since recycled aggregate includes aggregate,old hardened mortar and the interface between aggregate and old hardened mortar transition zone,if recycled aggregate is mixed directly into concrete,its performance is far inferior to that of ordinary concrete.Therefore,this paper attempts to fundamentally improve the basic properties of recycled aggregates by pre-treating recycled coarse aggregates with wrapping slurry to enhance the level of construction waste recycling and promote the green and sustainable development of the construction industry.The purpose of wrapping is to strengthen the weak area of interfacial transition zone of recycled coarse aggregate,based on this,52.5R ordinary silicate cement slurry,52.5R ordinary silicate cement-silica powder,42.5 sulfur alumina cement slurry and 52.5R ordinary silicate cement-42.5 sulfur alumina cement slurry are used to clad the recycled coarse aggregate respectively,and to study the basic physical properties of the aggregate and The shape characteristics of the modified aggregates were investigated by using digital image processing techniques.Then the treated recycled coarse aggregate was cast into concrete to study its mechanical properties and frost resistance,and to explore the effect of wrapping on the modification of recycled aggregate from the perspective of aggregate properties and concrete properties.(1)The surface microcracks of recycled aggregates were repaired by wrapping the recycled aggregates,and the basic physical properties of aggregates such as particle gradation,apparent density,water absorption and crushing index were improved.(2)The morphological analysis of the recycled coarse aggregate showed that the wrapping effectively improved the shape of the recycled coarse aggregate.The morphological characteristics of the recycled aggregates before and after slurring were normally distributed and had good fractal characteristics,and the results of shape analysis and relative surface roughness of the recycled coarse aggregates could be used as indicators for quantitative evaluation of the quality differences of the recycled coarse aggregates.The two-dimensional indicators including fractal characteristics can easily reflect the morphological characteristics of coarse aggregate by testing.(3)The recycled aggregate can be strengthened by the slurry pretreatment at the old interface and the secondary new interface,and the compressive strength,flexural strength and splitting compressive strength of recycled aggregate concrete can be improved to some extent.The post-folding compressive strength can better reflect the influence law of the clad aggregate on the concrete strength as well as the ordinary compressive strength.When the regularity of the ordinary compressive strength and splitting strength is not obvious,it can be reflected by testing the post-folding compressive strength and postfolding splitting strength.(4)The frost resistance of recycled concrete can be optimized and the loss of dynamic elastic modulus can be reduced by wrapping,in which the relative dynamic elastic modulus of wrapping with silicate cement-silica fume slurry decreases the least,and the frost resistance of concrete is optimal at this time.The frost resistance of recycled mixed concrete is related to many factors such as its internal pore structure,the age of freezing,and the strength of concrete,among which the most important factor is the pore structure,and the pore structure and strength of concrete depend mainly on the water-cement ratio and the maintenance method.