Experimental Study On The Durability Of Recycled Concrete Rich In Brick Coarse Aggregates

In today's rapid development of economic construction,the natural aggregate have been exploited excessively as raw materials to build new buildings.However,accumulating over a long period to mining has caused the drying up of natural raw materials.At the same time,a large number of abandoned old buildings not only has the serious influence of ecological environment,have caused a lot of waste of resources.With the contradictions of two big problem increasingly prominent,the occurrence of the recycled concrete for the paradox undoubtedly provides an effective solution.when we research recycled concrete,the cube compressive strength as the basic mechanical property,the c of it must be considered.Simultaneously,if we want to make good use of recycled concrete effectively for a long time,the durability problems is inevitable to consider as the key part of the service life of concrete.Aiming at the condition of the old buildings in hebei province contain a large amount of brick,and considering of the crushing index of brick aggregate is high as well as the water absorption of it is large,the compressive strength and durability of recycled concrete rich in brick aggregate are studied in this paper.Firstly,the basic physical properties of recycled aggregate rich in brick is studied and compared with natural aggregate.The research shows that the apparent density of recycled aggregate is 15.6% lower than ordinary concrete,but the crushing index and bibulous rate is far higher than the natural aggregate.At the same time,through the mature preparation technology of recycled aggregate,the aggregate gradation can meets the specification requirements.Then,this anticle mainly research the influence of recycled aggregate rich in 40% ~ 50% brick aggregate on the compressive strength,water permeability resistance,resistance to chloride ion permeability and freeze-thaw resistance of recycled concrete when the replacement rate is 0,40%,50% and 60%,and comparing with ordinary concrete.In addition,mixed with different amount of fly ash at the same time,researching fly ash on the modification effects of recycled concrete when the replacement rate is 0,10%,20% and 30%.By respectively establishing the relation of replacement ratio of recycled aggregate rich in brick aggregate and fly ash among the compressive strength,water penetration height,electric flux and the loss rate of relative dynamic elastic modulus,the test provides a reference for the practical application of recycled concrete rich in brick aggregate.In addition,under the action of the recycledaggregate and fly ash,finding out the optimal replacement rate of recycled aggregate rich in brick and the best dosage of fly ash.The research shows that the compressive strength and durability of recycled concrete rich in brick are worse than the ordinary concrete.An increasing number of recycled aggregate are to speed up the lower compressive strength and durability of recycled concrete,but can meet the engineering requirements with general resistance to water penetration,and resistance to chloride ion penetration.And freezing-thawing resisting level can reach the D100.Moreover,mixed with fly ash can reduce the compressive strength of recycled concrete,but can obviously improve its durability.When the replacement rate of recycled aggregate rich in brick is40%,and the dosage of fly ash is 20%,the durability of recycled concrete is best.