Research On Road Performance Of Coal Gangue In Cement Stabilized Crushed Stone Base

Coal gangue,as a hard rock with low carbon content that coexists with coal in the coal production process,is sorted out through washing and other processes during the coal production process and becomes solid waste.The discharge of coal gangue is relatively large,and it is generally piled up nearby to form coal gangue hills,occupying a large amount of farmland,and causing serious physical and chemical hazards.At the same time,the construction of the pavement base of high-grade highways requires a large amount of filling materials.Using coal gangue as base filling can effectively reduce the stacking of coal gangue,protect the ecological environment and reduce the construction cost of road projects.The social and economic benefits are huge.Therefore,in this paper,the washed coal gangue in Ningxia is crushed and screened and then mixed into cement stabilized crushed stone materials to provide a solution for the large amount of coal gangue stacking in Ningxia.Based on the determination of the basic physical and chemical properties of the raw materials,an indoor test was carried out on the road performance of coal gangue,and the substitution rate of coal gangue and the replacement of single-size crushed stone with cement stabilized crushed stone-coal gangue mixture were discussed.The impact of mechanical properties,a mechanical performance prediction model based on the design parameters of the mixture structure was established,and water stability,frost resistance and durability tests were carried out,and the application of coal gangue in the road base of high-grade highways in Ningxia was obtained.feasibility.The main research contents and conclusions are as follows;(1)Comprehensive evaluation of the engineering characteristics of coal gangue in Ningxia.The results show that coal gangue in Ningxia area can be used in the base layer.Its main component is carbonaceous shale.Its density is similar to that of natural gravel,but its water absorption rate is 4-5 times that of natural gravel.After crushing,the crushing value and pin pieces The shape content is large;the impact resistance is low and the firmness is poor;the ignition loss and the organic content are qualified.(2)Research on the structural design parameters of cement stabilized crushed stone-coal gangue mixture.According to the 7d unconfined compressive strength,the optimal gradation of the mixture is determined to be 20～26.5 mm:10～20 mm:5～10 mm:0～5 mm=0.18:0.275:0.18:0.365.On the basis of the best gradation,4%cement dosage was determined according to the trial mix results.(3)Research on the mechanical performance parameters of cement stabilized crushed stone-coal gangue mixture.The results show that the unconfined compressive strength,splitting strength and compressive resilience modulus of the mixture all decrease with the increase of coal gangue replacement rate;specimens after 10-20 mm and 0-5 mm crushed stones are replaced The mechanical properties of the mixture have decreased significantly;the relationship model between the design parameters of the mixture structure and the mechanical properties has been established,and the relationship model between the unconfined compressive strength and the splitting strength,and the compressive resilience modulus has a good degree of fit.(4)Research on the durability of cement stabilized crushed stone-coal gangue mixture.The results show that the substitution rate of coal gangue and the substitution of coal gangue for different single-sized crushed stones have little effect on the water stability of the mixture;from the perspective of the appearance,mass loss rate,and strength loss rate of the specimen before and after the freeze-thaw cycle test,each The mass loss rate of the coal gangue replacement rate group is far less than the 5%limit,and the strength loss rate is less than 40%.The freeze-thaw cycle test was carried out on coal gangue instead of different single particle size crushed stones.The results showed that the mass loss rate and unconfined compressive strength loss of the mixture specimens after 0～5mm and 10～20mm particle size coal gangue were mixed Rate performance is poor.