| China is a big steel producing country,and a large amount of steel slag is produced every year.The use of steel slag in road engineering can not only effectively solve the problems of land occupation and environmental pollution caused by its stacking,but also can replace a large number of road construction resources,reduce environmental damage such as excavating rocks from mountains,digging land and soil,and realize the effective utilization of industrial solid waste.This paper takes the steel slag produced by Shaanxi Longmen Iron and Steel Group as the object,and studies its feasibility for roadbed filling and its influence on the base strength and shrinkage cracking performance when it is used for cement stabilized macadam.First of all,in view of the long test period of the water immersion expansion test that steel slag needs to be used in road engineering,the relationship between them is determined by measuring the content of free calcium oxide in different steel slag and the corresponding immersion expansion rate,and the method of predicting the immersion expansion rate by indoor titration experiment is proposed,which is convenient for the application of steel slag in practical engineering.Secondly,the feasibility of using steel slag for roadbed filling was studied from two aspects of mechanical properties and environmental impact.The results showed that when steel slag was used for roadbed,its mechanical properties were excellent,the California bearing ratio of the sample under 95% compaction is 133.7%,and the modulus of resilience is 154 Mpa,it can meet the related requirements of subgrade filling.The concentration of harmful metal ions in the leachates after immersion meets the requirements,but there is a problem that the p H value of the leaching solution is too large,which will affect the environment.The carbonization degree of the steel slag surface can be improved by spraying deionized water and 0.005mol/l Na OH solution,so as to reduce the p H value of the leaching solution.By using 2 kinds of cement dosage(3.5%、4.0%)and 4 kinds of steel slag mixing ratios(0%、30%、45%、60%),the cement dosage of cement-stabilized steel slag macadam is determined to be 3.5% based on compaction test and 7d unconfined compressive strength test,and the 4 kinds of mixing ratios are further developed research on the strength and shrinkage cracking performance of cement-stabilized steel slag macadam base.In order to study the influence of different steel slag content on the mechanical properties of cement-stabilized steel slag macadam,the compressive strength tests with ages of 7d,28 d,and 90 d,the splitting strength tests and compressive modulus of resilience test with ages of 28 d,60d,and 90 d were used.The results show that the compressive strength,tensile strength and compressive modulus of resilience of cement-stabilized macadam at different ages are increased by18.5%～75.8%,6.1%～64.3%,and 32.5～80.4% respectively after mixing 30%～60%steel slag.Through drying shrinkage test and temperature shrinkage test,the volume shrinkage characteristics of cement stabilized macadam under different steel slag content were studied.The results showed that adding steel slag can significantly reduce the drying shrinkage coefficient of cement stabilized macadam by19.7%～57.3%,but increased the temperature shrinkage coefficient,an increase of9.6% to 29.8%.In order to further study the effect of adding steel slag on the shrinkage and cracking properties of cement-stabilized macadam,the average crack spacing and crack width of the base layer under different steel slag content were calculated.The results show that compared with cement-stabilized macadam without steel slag,adding 30%～60% steel slag can increase the crack spacing by 9.6%,21.2%and 48.9% respectively;the crack width first increases by 10.6%,and then decreases by 1.4% and 5.6%.Considering the mechanical properties and shrinkage characteristics of cement-stabilized steel slag macadam,it is recommended that when it is used in the base course of secondary roads,the dosage of water-stabilized macadam cement mixed with steel slag is 3.5%,and the amount of steel slag is 60%.The research results have a guiding effect on the application of Longmen Iron and Steel Group in road engineering,and also provide reference for the application of steel slag in road engineering in other parts of China. |
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