Study On Application Of Tuff Tunnel Slag In Middle Surface Layer Of Chao-Hui Expressway

There are many tunnels in Chao-Hui Expressway in Guangdong province.A lot of tunnel slag is produced in the tunnel construction.In order to protect the environment,save natural resources and improve economic efficiency,in this paper,through the analysis of tunnel slag lithology and processing technology,the feasibility of applying hole crushing process to the middle surface of asphalt pavement is researched.The main work and conclusions are as follows.Firstly,the processing technology and crushing method of tuff hole slag are introduced.It is concluded that the improved two stage process can be used to improve the aggregate quality.On this basis,the main mineral composition and chemical composition of the stone made from the tunnel hole slag are analyzed.The results show that the major components of tunnel slag containing rhyolite,andesite,feldspar and quartz class rhyolitic ignimbrite,chemical components including SiO2,Al2O3,Fe2O3 etc.Secondly,through the physical and mechanical properties test of tuff aggregate,the results show that the aggregate density of tuff is about 2.7 g/cm3,the coarse aggregate is about 6%～7%,and the water absorption rate is less than 1%.In addition,the compressive,wear resistance and other characteristics was well,all indicators met the requirements of aggregate on the physical and mechanical performance.Then,three types of GAC-20C mixture are designed with tuff and crushed stone.The road performance of the prepared GAC-20C mixture was studied,the results showed that GAC-20C mixture dynamic stability reached 10000 times/mm,high temperature performance is well;At the same time,three kinds of mixture Marshall residual stability and freeze-thaw splitting strength were higher than the standard value,meet the requirements of performance;and the low temperature test showed that each GAC-20C mixture at low temperature bending the average strain value reached 2800με,higher than 2500με were obtained through technical indicators;Through seepage coefficient test,it is found that the water permeability coefficients of three gradation mixtures are 28.1ml/min,29.6ml/min and 25.1ml/min respectively,GAC-20C mixture water tightness and meet the requirements.Finally,according to the construction of the test section of Chao-Hui expressway,the GAC-20C mixture construction quality is good,the subsequent performance meet the design requirements,and the application of slag hole tuff has obvious social and economic benefits in asphalt pavement construction.