Study On Properties Of Cement Stabilized Crushed Stone And Steel Slag Mixture Based On Surface Modification Technology

At present,China is relatively short of natural resources,resulting in the gradual increase of the cost of raw materials used in highway construction.As a solid waste building material,steel slag has the characteristics of low material price and good mechanical properties.However,the practical engineering experience in recent years shows that the volume stability of steel slag is the main factor restricting the wide application of steel slag in highway construction.Therefore,the research on the method of restraining the volume expansion of steel slag can not only improve the performance of cement stabilized crushed stone steel slag mixture,but also improve the resource utilization rate of steel slag in highway construction.Aiming at the problem of insufficient volume stability of steel slag,the surface modification technology of aggregate is used in this thesis.Two kinds of modifier materials,methyl potassium silicate and silicone acrylic emulsion,are selected to modify the surface of steel slag.Compared with three factors,such as modifier concentration,modification time and size of steel slag,the surface modification technology has good effect on water absorption,hydrophobicity and crack resistance of steel slag.Volume stability and performance improvement.The results show that the water absorption of steel slag decreases to the lowest when the concentrations of potassium methylsilicate and silicon propylene are 3wt% and 12wt% respectively and the immersion treatment time is 12h;In hydrophobicity test,the modification effect of potassium methosilicate solution is better than that of silicone acrylic emulsion.In the water erosion test and water immersion expansion rate test,the expansion cracking rate and water immersion expansion rate of modified steel slag with different particle sizes are better than those of unmodified steel slag,and the expansion rate of potassium methylsilicate modified steel slag with particle size of 4.75 mm ～ 9.5mm is28.7% lower than that of unmodified steel slag.Through SEM observation,it is found that the surface structure of the modified steel slag is relatively flat and the pores are filled,indicating that the surface modification can modify the surface structure of the steel slag.Based on the test results of the relevant properties of the modified steel slag,the modified steel slag with better performance is selected.The natural coarse aggregate is completely replaced by the modified steel slag with potassium methylsilicate by the equal volume substitution method,which is applied to the steel slag mixture of cement stabilized macadam.Through the 7d unconfined pressure resistance test,the feasibility of replacing the natural macadam with the modified steel slag with potassium methylsilicate is preliminarily studied,The results show that the compressive strength of the mixture is low when the modified steel slag completely replaces the natural gravel;To solve this problem,this thesis combines the mineral fine admixture method with surface modification to carry out composite modification treatment on the steel slag.It is designed to adopt 10% fly ash and 4 kinds of steel slag replacement methods,and form 20 kinds of mixture proportions with 2 kinds of cement dosage.Based on the 7d unconfined compressive strength test results,16 kinds of better proportions are optimized,The expansion rate of the optimized modified steel slag mixture was tested.Then,through unconfined compressive strength,compressive resilience modulus,indirect tensile strength test,freeze-thaw test and dry shrinkage test,the improvement effects of modified steel slag on the mechanical properties,frost resistance and dry shrinkage and crack resistance of the mixture are studied respectively.Finally,it is determined that the best mix proportion of the mixture is 5% cement + 10% fly ash The replacement method is 4.75 mm ～9.5mm modified steel slag to replace the ordinary steel slag in the same gear,the coarse aggregate in other gears still adopts ordinary steel slag,and the fine aggregate below 4.75 mm adopts limestone.