| In recent years,along with the development of economy and transportation,the pavement of unmodified asphalt concrete can not satisfy the development of traffic and vehicle load. The early water damage has happended in lots of pavement which was put into use. Unreasonable gradation of asphalt mixture is one of the main reasons.SAC is a kind of good performance asphalt concrete,which was developed by our country in 1988,and has got very good economic benefit in lots of engineering applications. But there are somethings to be advised of the design method of SAC .For example,for all the SAC mixture,4.75mm is the aggregate cut-off point;Coarse aggregates and fine aggregates are all designed by modified Fuller formula.This paper has a systematic study in the aggregate cut-off point of SAC13 by means of orthogonal test, and the result show that 2.36mm being used to be the aggregate cut-off point is more reasonable.On the basis of this,coarse aggregates are designed by the method of filling and fine aggregates are calculated using modified Fuller formula;The dosage of asphaltum is confirmed through laboratory run-off test and cantabro abrasion test and Marshall test;Then using the method of VCAdrf to adjust and get the objective gradation of the asphalt mixture. And then study the effect of various of modified materials such as cement,slag powder, lignin fibers and so on which improve the water stability of SAC.The test results show that using cement to replace the 1/3 mineral powder as filler can effectively improve the;The effect of using slag powder to replace mineral powder to improving the water stability of asphalt mixture is not marked,but it can improve the water stability of asphalt mixture in theory.To found out its definite influence to the water stability of asphalt mixture,it need to adjust the dosage of asphaltum and slag powder.Adding lignin fibers to the asphalt mixture can improve its water stability ,this effect is better than cement's. |
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