Study On The Performance Of Recycled Coarse Aggregate Asphalt Concrete

According to the China Construction Waste Resource Industry Development Report in 2014,there are more than 1.5 billion tons of construction rubbish produced each year in china.And most of them are cement concrete blocks,mortar,broken brick,ceramic and other solid waste.The construction or road aggregate is the main use form of solid waste.As we all know,it takes a lot of sand and gravel resources in roadworks.And the demands for aggregate will change with the road grade and structural depth changes.The requirements of aggregate are relatively more stringent in asphalt concrete.However,the composition of recycled aggregate from different sources is quite different and the variability of aggregate performance is great.The recycled aggregate produced by the demolition of roads and bridges is basically pure cement concrete composition.The quality of the aggregate is also better than the recycled aggregate in the form of brick and concrete.Therefore,the application of recycled aggregate in road engineering should be used differently.Asphalt concrete pavement is the common type of pavement.In recent years,it is trying to use asphalt gravel and other flexible grassroots in Guangdong Province.For that,two typical asphalt mixture types which are AC-20 C and ATB-25,were selected to study the variation of road performance and compaction characteristics of asphalt concrete with different recycled coarse aggregate content in this paper.The experimental results show that the high temperature performance of asphalt concrete increases with the increase of recycled coarse aggregate content and then decreases.And the maximum is in the content of 30% ~ 40%.The results of water stability test show that the addition of recycled coarse aggregate has a positive effect on the stability of asphalt concrete.The residual stability and the freeze-thaw splitting strength ratio reached the maximum at the content of 60% ~ 70% and the test result at 100% content was almost the same as that of pure natural aggregate asphalt concrete.Besides,it was found that the addition of recycled coarse aggregate had some negative effects on the low temperature performance and fatigue resistance of asphalt concrete but decreased less at the content less than 60%,which is proved that the effect of blending coarse aggregate on the low temperature performance and fatigue resistance of asphalt concrete can be controlled.Compared with pure natural aggregate asphalt concrete,recycled coarse aggregate asphalt concrete is more difficult to compact.Therefore we should pay attention to increase the recycled coarse aggregate asphalt concrete compaction.The important reason that the recycled coarse aggregate has a positive effect on the high temperature performance and water stability of the asphalt concrete is that the cement mortar increases the adhesion of the aggregate to the asphalt.In order to study the effect of mortar on the adhesion,the tensile test was designed to change the contact area between the mortar and the asphalt.The change of the pulling force shows that the larger the contact area between mortar and asphalt the greater the pulling force.Then based on the surface energy theory,the contact angle between mortar、granite and asphalt was measured,which show that the asphalt is more likely to adhere to the mortar.And the adhesion between them show that the asphalt and mortar adhesion work is also greater than the asphalt and granite adhesion work.