Influence Of Steel Slag Aggregates And Reclaimed Asphalt Pavement On Hot-mix Asphalt Pavement Performance

At present,China has the world’s first freeway mileage.As a result of Pavement renovation and maintenance,a large number of reclaimed asphalt pavement（be short for RAP）will be produced every year.Discarding these RAP materials will not only cause damage to the natural environment,but also a great waste of resources.The problem can be solved by using recycled asphalt mixture technology to treat RAP materials.Steel slag is a by-product of the steel industry,with the growth of steel production,the problem of large amounts of steel slag accumulation needs to be solved urgently.Steel slag has excellent mechanical properties,is strong and wear-resistant,and has strong adhesion to asphalt which can be used as aggregate in asphalt mixtures.This paper uses layered recovery to handle RAP,while adding steel slag,and on this basis to study its pavement performance,the main work content is as follows:（1）In this paper,large pieces of reclaimed asphalt pavement materials are processed by manual layering and crushing.The RAP suffer less damage,the internal materials of RAP are less affected by the outside world,and the asphalt aging degree is low.Analyze the physical parameters,mechanical properties and gradation curves of RAP,steel slag and new materials.It is found that steel slag has a higher density and water absorption.The water absorption rate of steel slag with a particle size of 4.75mm to 9.5mm is 3.11%,and the water absorption rate of steel slag with a particle size of 1.18mm to 2.36mm is 5.55%.The water absorption rate increase with the particle size decrease.The increase of water absorption will absorb more asphalt,so steel slag is not suitable for use as fine aggregate.（2）Using the Marshall design method,the optimal asphalt content under different steel slag and RAP content were obtained.When the RAP content is 30%and the steel slag content is 5%,10%,15%and 20%respectively,the optimal asphalt content of the steel slag hot recycled asphalt mixture are 3.98%,4.31%,4.37%and 4.46%,respectively.The bulk density are 2.484,2.491,2.513 and 2.536 respectively,and the unit is g/cm³.When the steel slag content is 10%and the RAP content is 40%and 50%,the best oil-stone ratios are 3.99%and 3.11%,respectively.The oil-stone ratio and bulk density of the steel slag hot recycled asphalt mixture increase with the increase of the steel slag content.（3）The pavement performance test of the steel slag hot recycled asphalt mixture was carried out under different RAP and steel slag mixing ratios.When the RAP content is less than 50%,the high temperature stability of the hot recycled steel slag asphalt mixture meets the specification requirements.When the RAP content is 30%and the steel slag content is5%,10%,15%,and 20%,the maximum flexural strain(×10^-6)of the trabecular specimens in the trabecular low-temperature bending test are 2046,2394,2407,and 3259,respectively.The tensile strength ratios of Marshall specimens in the freeze-thaw split test were 99.1%,99.1%,85.6%and 89.4%,respectively.The addition of steel slag can improve the low-temperature crack resistance of the recycled asphalt mixture,but it will reduce the water stability;When the steel slag content is 10%and the RAP content is 30%,40%,and 50%,the maximum flexural strain(×10^-6)in the low-temperature bending test of the trabecular is2394,3027 and 2040,respectively.The tensile strength ratios in the split test were 99.1%,93.5%and 88.6%,respectively.Through the road performance test results,it can be obtained that when steel slag is mixed into RAP,the replacement rate of new materials can reach 50%.This data can provide a reference for the design of recycled asphalt concrete.Function fitting and analysis of the road performance test data,and the following results are obtained:when the RAP content is 30%,the critical value of the steel slag blending rate is 15.7%;When the RAP content is 30%,the critical value of steel slag blending rate is 15.7%;when the steel slag content is 10%,the critical value of RAP blending rate is 49.7%.The replacement rate of new materials can reach 59.7%.