| With the establishment of the "double carbon" target and the implementation of the "no waste city" pilot program in recent years,industrial solid waste resource utilization has become a social hot area.On the other hand,with the building and growth of infrastructure such as highways,the demand for base filling materials is expanding.Natural sand and gravel mining causes environmental issues such as slope exposure and vegetation degradation,which cannot be disregarded.This disseration fully exploits the properties of granulated blast furnace slag powder(S95 grade),which is easily ignited in an alkaline environment to generate hydraulic cementing activity.Then it is mixed with three types of solid waste materials:spontaneous combustion coal gangue,fine particle size steel slag(mainly below 4.75 mm),and asphalt mixing station recycling powder generated in a mining location in Handan,Hebei Province.Through experimental research,the performance of a unique type of pavement foundation slag powder stabilized solid waste(coal gangue,steel slag,recycling powder)mixture was investigated.The following are the key research findings:(1)The related material properties of three types of solid wastes are researched using field sampling and indoor tests,and the basic performance technical indexes of slag powder are introduced.The results reveal that the raw material indexes match the specification requirements.(2)After designing 6 groups of mixture ratio(mass ratio)by uniform design method,the 7d unconfined compressive strength,120 d compressive rebound modulus and 120 d splitting strength of each test group were tested respectively.Based on the experimental tests of six different mixture ratios(mass ratios)and data regression analysis by using JMP software,the mathematical models are established between the content of each mixing factor and the three mechanical properties indexes.Results show that the mechanical properties of the mixture improve as the amount of steel slag in it increases.Furthermore,as the recycled powder content increases,the early mechanical strength gradually decreases,whereas the later mechanical strength increases first and then decreases.In addition,the regression equation has a high degree of fit,which can provide a reasonable ratio for the selection and design of pavement base and bottom base of various grade highways,and has practical significance for guiding practical engineering applications.(3)The Image J software,which is based on digital image processing technology,is used to process the splitting section image.The primary reasons for the difference in the strength of the combination with different proportions are evaluated from the meso level by evaluating the morphology,gradation,amount,and spatial distribution of the components inside the specimen structure.The results reveal that the admixture content has a considerable impact on the mechanical strength of the mixture.The splitting section of the high mechanical strength mixed specimen is reasonably flat.The image indicates that the coarse and fine aggregates are evenly distributed throughout the specimen,the inter-aggregates are compressed,the gaps are completely filled with slurry,and the structure is very dense.(4)The proportion of some uniform mixture test groups was chosen,and the freezethaw cycle test was performed to evaluate its durability.The dry-wet cycle test was planned and executed to investigate its water stability.Simultaneously,the volume stability of a steel slag aggregate mixture was determined using an immersion expansion rate test.The results suggest that the mixture is durable and stable.The research results not only provide a theoretical foundation for high-value practical roadway engineering applications of industrial solid waste,but also have significant environmental and social implications for practical application. |
