Research On The Effect Of Aggregate On The Performance Of Cold Patch Asphalt Mixture

Cold mix asphalt, a new kind of pavement repair material, can be inroom temperature or low temperature on the pavement to be repaired. Butnow, the strength and water stability of cold mix asphalt inland are bad.The road surface is subject to early damage: rutting and water damageand so on. In this paper，we studied the strength and water stability ofcold mix asphalt, and analyzed the formation mechanism of strength andstick-spalling. The aim of this paper is to find a way to improve thestrength and water stability of cold mix asphalt through the choice ofaggregate, filler, gradation mode and the parameters optimization. Mainworks of this paper are follows:First, optimal design of the gradation mode combined withsuccessful experience at home and abroad was done successfully, and theamount of asphalt, different modifiers and different gradations on theperformances of cold mix asphalt was analyzed. Second, different typesof aggregates (basalt, limestone, diabase), elongated particle content,mixing temperature and different compaction on the performance of coldmix asphalt was studied carefully. Third, the amount of filler, differenttypes of fillers and different mixing processes on the performance of coldmix asphalt was studied in detail. As a comparison, hydrated lime wasused to replace part of filler, and then the effect of the water stability, andthe different mixing processes on the water stability was also studied.The following main conclusions can be drawn:1. From the comparison of strength and water stability at differentgradation modes, the self-designed gradation is the best, and the optimumamount of cold asphalt is5.0%. The initial Marshall Stability (MS) andmolding MS of the mixture are5.45kN and10.73kN, and the residualstability is92.7%.2. The performance of the lime stone is the best among theaggregates, and the initial MS and molding MS are5.52kN and10.52kNrespectively, and the residual stability is98.2%. Elongated particle content increased from5%to30%, and the initial MS, molding MS andresidual stability respectively by41.4%,37.7%and17.4%. Mixtemperature increased from30℃to60℃, and the initial MS, moldingMS and residual stability are increased by10.2%,30.0%and10.1%.Compaction times increased from60to105, and the initial MS, moldingMS and residual stability are increased by32.0%,29.0%and6.9%respectively.3. From the evaluation of comprehensive performances， theoptimum amount of filler is3%. The strength of cold asphalt mix is thebest when silicon as filler, and the initial MS and molding MS are5.67kNand11.98kN respectively. The water stability of cold asphalt mix is thebest when cement as filler. Hydrated lime is used to replace part of filler,which can improve the water stability of cold mix asphalt. The optimumamount of hydrated lime is1%, and the water stability is88.2%. Whenold asphalt was prepared by non-modified asphalt matrix, differentmixing processes have different effects on the performances of cold mixasphalt. Results indicated that the optimal selection of aggregate is themixture of hydrated lime slurry and aggregate, and the water stability is96.1%.