Laboratory Experimental Study On Geotechnical Properties Of Tire-Derived Aggregate—Weathered Rock Material Mixtures

With the high-speed development of economy,there are more and more cars in our lives.Waste tires,as a flammable and nondegradable material,contaminate the natural environment a lot.The problem of "Black Pollution" caused by waste tires becomes increasingly prominent.There are many methods to deal with waste tires,such as the use of entire tire,air storage,landfill,burning,pyrolysis,retreading.and physical broken and so on.However,low recovery rate of waste tires,high energy consumption and secondary pollution during reprocessing are worthy of consideration.Scarce rubber sources exist in China.The development of waste tires recycling industry cannot keep up with that of automobile industry and cannot fit with the requirement of severe environment situation.Therefore,dealing with waste tires in proper way and reducing environmental pollution are of great urgency.Tire-derived aggregate(TDA)have many advantages,such as lightweight,durable,nondegradable,high-strength,good adsorbability and drainage and so on.TDA as backfill materials,adsorbing mediums and isolation materials,are mainly used in road embankment,retaining wall,bridge abutment and anti-frost-heaving layers.TDA can enhance bearing capacity and reduce the settlement deformation of structures.TDA mixed with soil generate lightweight materials,which can improve the soil engineering properties.In this research,weathered rock material(WRM)and TDA were used,and a series of laboratory tests were conducted.Based on the properties of WRM and TDA,the geotechnical characteristics of mixture were studied.WRM was mixed with different quality fractions of TDA to prepared different moisture contents mixture.Heavy compaction tests were conducted using large size compaction equipment.The curves of dry densities versus moisture contents were obtained from tests.Test results indicate that adding tires chips can significantly reduce the mixture weight and the amount of water.In addition,the compaction curves are quite different from type compaction curves with the quality factions of TDA increasing.By means of comparison and analysis,the compaction mechanism of mixture is studied.In order to study the compress behavior of mixture with different quality fractions and moisture contents under vertical stress.Compression tests were conducted with mixture under lateral confined condition.Test results show that the maximum permanent strain appears in the first unloading-reloading cycle and permanent strain decreases in the subsequent cycles.With TDA increasing,the overlap ratio of compression curves and rebound curves increases.Large compression strain significantly indicates large settlements for structures under vertical load.When quality fraction of TDA is low,the effect of moisture content on permanent deformation of mixture is more significant.However,the sensitivity of mixture to water decreases with TDA increasing.A large size variable head permeameter has been developed in this study to fit with large size TDA mixture.Permeability tests were conducted to study the permeability of mixture with different quality fractions and moisture contents.Permeability coefficients obtained from tests show that permeability of mixture increases due to TDA.The minimum permeability of mixture with low quality fraction of TDA is obtained in the optimum moisture content,because of small porosity in mixture.When the quality fractions of TDA is large,permeability coefficients increase and permeability of mixture enhance significantly with TDA and moisture contents increasing.