Study On The Corrosion Law Of Calcium In Cement Stabilized Macadam

Inorganic binder stabilized base is the main structural type of pavement base in our country.It has been found that inorganic binder stabilized base is prone to water damage in engineering for a long time,which is mainly manifested as dissolution and erosion loss.In order to prevent the water damage of the base,cement stabilized macadam base is mainly used,and the content of fine-grained soil is limited.Cement stabilized macadam base gradually becomes the dominant type of base.The strength of base material gradually increases,and the thickness of base gradually increases.Due to the interlayer combination and easy cracking,the water damage problem of cement stabilized macadam base still can not be completely solved.The main reason is the dissolution degradation of base material The mechanism is not completely clear,and the targeted measures are not strong.Due to the influence of rainwater infiltration and groundwater,the dissolution and looseness of pavement structure are inevitable,so it is necessary to study the dissolution mechanism of cement stabilized macadam base.In this study,accelerated dissolution test in 6m ammonium chloride solution was designed by using accelerated dissolution test method.The effects of cement dosage and fly ash dosage on the change of dissolved calcium ion concentration,porosity and permeability coefficient were studied.The calcium dissolution model in cement stabilized macadam was established and compared with the test results,and the parameters in the model were analyzed numerically.The main research results are as follows（1）The results show that the leaching of calcium ions increases with the increase of cement content,but the increase of cement content reduces the calcium ion leaaching rate of the material.The addition of fly ash can effectively improve the anti-leaching ability of cement stabilized macadam,but the effect of fly ash is different under different cement content.（2）The porosity of cement stabilized macadam can be reduced by increasing the dosage of cement and fly ash.The porosity increases with the increase of dissolution time,but the change of porosity is not obvious in the whole dissolution process,which is mainly controlled by the initial porosity.The permeability coefficient of cement stabilized macadam has almost no change in the whole dissolution process.The equivalent pipe model,percolation and scaling properties are used to analyze it.（3）Comparing the model results with the test results,the results show that the calcium ion leaching model results are in good agreement with the test results,but in the later stage of the corrosion test,the difference is relatively large.There is a big difference between the porosity model results and the experimental results,but the overall change is still very small,which has little influence on the model.（4）The parameter analysis of the model shows that the x₁value has no effect on the model results due to the short model time.x₂value mainly affects the dissolution stage of calcium hydroxide.The C_satuvalue mainly affects the process of calcium hydroxide and the dissolution rate of calcium silicate hydrate in the model.The change of k_vvalue can significantly affect the dissolution rate and dissolution of calcium ions.The different calculation methods of diffusion coefficient will inevitably lead to the model The difference of results shows that the change of the value of the results has little influence on the results of the model when the time step and the spatial step size do not affect the continuity of the model results.