Experimental Study On Mechanical Properties And Impermeability Of Recycled Rubber Concrete

Under the background of people’s attention to the construction of ecological civilization,the construction industry has been unable to fully satisfy the industry demands by large-scale exploitation of natural sand and gravel.In order to solve the contradiction between supply and demand of building materials,new green concretes,such as recycled concrete and rubber concrete,have gradually come into people’s vision.First of all,waste concrete from a wide range of sources contains a large number of sand-gravel mixtures,which can be broken into recycled aggregates.At the same time,rubber particles can be obtained by recycling waste rubber tires to prepare rubber concrete,which has better toughness and impermeability than ordinary concrete,and may also play a supplementary role in recycled concrete.In the thesis,instead of natural stone and natural river sand respectively,recycled coarse aggregate and rubber particles are used to prepare recycled rubber concrete.Through the performance experiments of workability,mechanical properties,water permeability and chloride ion permeability of concrete mixtures,the effects of recycled coarse aggregate and rubber particles on mechanical properties and permeability of recycled rubber concrete are obtained as follows.(1)Recycled coarse aggregate is coated with old cement mortar and has rough surface and high crushing value.The fluidity of concrete mixtures and decreases with the increase of replacement ratio of recycled coarse aggregate,and hence the slump decreases.The fluidity of concrete mixtures can be obviously enhanced by adding rubber particles,and the slump also increases with quantity increase of rubber particles.(2)In terms of mechanical properties,the experiment shows that the brittle failure characteristics of concrete becomes more obvious as the replacement rate of recycled coarse aggregate increases.The plasticity of concrete can be increased by adding rubber particles.The results also demonstrate that the cubic compressive strength,flexural strength,axial compressive strength and elastic modulus of concrete decrease with the increase of recycled coarse aggregate and rubber particle content.The decline rate of mechanical properties accelerates when the rubber content is more than 10%.(3)Two different permeability tests present that the impermeability of concrete decreases with the increase of replacement rate of recycled coarse aggregate.With the increase of rubber particle content,the impermeability of concrete increases first and then decreases.The impermeability of concrete with 40% replacement rate of recycled coarse aggregate is similar to that of ordinary concrete,and best performance is achieved with 10% content of rubber particles;the impermeability deteriorates rapidly with 70% recycled coarse aggregate,and takes best value when 5% rubber particles are mixed.(4)The water permeability test and chloride ion permeability test of rubber recycled concrete have good correlation in results,but high dispersion is found with high permeability.The relationship between compressive strength and chloride ion impermeability is also evaluated.Only changing the recycled coarse aggregate content,the impermeability of concrete shows a good linear correlation with the strength.However,it is not appropriate to evaluate the impermeability using strength when only rubber particle content changes.