The Research Of Crack Control Measures Of Rural Road When Overlaying Asphalt Layer On The Old Cement Concrete Pavement

Asphalt over layer on the concrete pavement can improve the performance and fatigue life of road,to meet the traffic needs,so it's the most common way of rebuilding for the old cement concrete pavement.But there are joints and cracks,and under the influence of seasonal environment temperature and vehicle load,which lead to new cracks along rebuilding pavement.And that's the reflection crack,it will speed up the damage of the pavement structure,shorten the life of the rebuilding road,all these will lead to a negative impact on transportation and the economy.Therefore,it's crucial to study the crack control measures,when overlaying asphalt layer on the old cement concrete pavement to rebuild a rural road.This dissertation mainly study the anti-crack performance of the rural road by indoor wheel load test,which overlaying AC-13,SMA-13 asphalt mixture on the old cement concrete.First,designing the proper mixing proportion for these two kinds of asphalt mixes.Then tests carry out respectively under 0.7Mpa,1.05 Mpa,1.4Mpa wheel load.Finally,comparative analyze the anti-crack performance before and after laying anti cracking interlayer,include fiberglass grids,geotextile interlayer,fiberglass-polyester paving mat.This dissertation also explain the causes and extended process of reflection cracks,through the finite element software ANSYS to simulating geotextile as a anti-crack layer,and simulating the stress state when overlaying asphalt layer on the seams of the old cement concrete pavement,to analyze the delay performance of geotextile interlayer for reflection cracks.This dissertation also conclude the measures to prevent the uneven settlement of the overlayed oasphalt on the old cement pavement in rural roads,and briefly introduces the construction craft on widening the asphalt layer for the old cement pavement.The results and theoretical analysis show that will be effective to apply geotextile interlayer to prevent the reflection crack for old cement concrete pavement,also get the following conclusion:(1)When overlaying AC-13 and SMA-13 to rebuild the old cement concrete pavement,set the geotextile as a interlayer can effictively delay the onset of reflection crack,and their effects is compared as below: fiberglass grids> geotextile interlayer >fiberglass-polyester paving mat.Under the same conditions,the old cement concrete pavement with the same thickness of the AC-13 asphalt mixture layer is easier to form reflective cracks than the additional SMA-13 asphalt mixture layer.(2)Under the standard load of 0.7MPa,the comparison for the effect of preventing reflection crack as below: SMA-13 asphalt mixture layer + fiberglass grids >AC-13 asphalt mixture layer + fiberglass grids > SMA-13 asphalt mixture layer + geotextile interlayer > SMA-13 asphalt mixture layer + fiberglass-polyester paving mat >AC-13 asphalt mixture layer +geotextile interlayer >AC-13 asphalt mixture layer +fiberglass-polyester paving mat.(3)Under the heavy load 1.4MPa,the comparison for the effect of preventing reflection crack as below:SMA-13+ fiberglass grids is the best,AC-13 + fiberglass grids comes second.SMA-13 + geotextile interlayer,SMA-13 + fiberglass-polyester paving mat,AC-13 + geotextile interlayer,and AC-13 + fiberglass-polyester paving mat are less effective for preventing reflection crack.(4)The finite element analysis of the ANSYS shows that geotextile interlayer can obviously reduces the load stress and the temperature stress at the seams of betweene the old cement concrete pavement and the asphalt overlay,to avoid the stress concentration.