Performance Evaluation Of Cement Stabilized Recycled Concrete Aggregates Treated With Waste Oil And Asphalt Emulsion

In order to improve the anti-crack properties of cement stabilized recycled concrete aggregates in base layer,two treatment methods for recycled mixture were proposed.One was to change the interface characteristics of recycled coarse aggregates through waste oil.Another was to stabilize compositely the granular mixture using cement and asphalt emulsion.The performances of three recycled mixtures,i.e.,conventional mixture,waste oil treated mixture,and asphalt emulsion treated mixture,were evaluated systematically by a suite of laboratory tests and the effects of both treatment methods were compared comprehensively.The main work and conclusions are as follows:First,the basic properties of various raw materials were researched.The test results showed that compared with the natural aggregate,the recycled aggregates had a smaller apparent density,bigger water absorption and crushing value,and similar content of flat and elongated particle.For recycled coarse aggregates,the apparent density and water absorption increased with an increase in grain size.However,the change trends of flat and elongated particle content as well as soft stone content with the increase of particle size were not obvious.Secondly,the proportioning design of three recycled mixtures was carried out and its vibratory compaction characteristics were studied.The test results showed that both treatments decreased the optimum moisture content of mix and the waste oil treatment caused a greater reduction compared to the treatment with asphalt emulsion.On the other hand,the waste oil treatment increased the maximal dry density of mix,but the asphalt emulsion treatment resulted in a slight decrease.Thirdly,the mechanical properties tests were conducted on three recycled mixtures.The test results and analyses showed that the compressive strength and tensile strength of three recycled mixtures increased with the growth of curing time.Two treatments reduced the strength of mixture to some extent and the strength of mixture treated with waste oil was the lowest.However,the asphalt emulsion and waste oil treated mixture had a faster increase in strength after 7 days and 28 days of curing,respectively.In addition,both treatments effectively reduced the compressive resilient modulus of mixture and this decreases was much pronounced for waste oil treated mixture.Finally,the pavement performances tests were undertaken on three recycled mixtures.Test results and analyses showed that three recycled mixtures had a good resistance to freezing.The fatigue life of two treated mixtures was higher at medium and low stress ratios,but its stress sensitivity was also higher.The conventional mixture had a better fatigue properties under the condition of high stress rate.The drying shrinkage performances of mixture were improved significantly after treatments and waste oil treatment produced a better effect as compared to asphalt emulsion treatment.Furthermore,both treatments also caused a slight improvement to temperature shrinkage properties of mixture.