Research And Application Of Road Base Material Prepared By Porous Coal Gasification Slag(PCGS)

Porous coal gasification slag(PCGS)is a kind of solid waste discharged from the coal chemical industry.It is of great significance for saving natural resources and protecting the ecological environment by processing PCGS into road base aggregate.However,PCGS aggregate has large crushing value which causes it is easily crushed under forming pressure and road base material prepared by PCGS has lower strength than that prepared by crushed stone.Meanwhile,the water absorption of PCGS aggregate is high,it still remains unclear how this affects the frost resistance and drying shrinkage resistance of the PCGS road base material.Aiming at solving above-mentioned problems,and based on the basic physical and chemical properties of the PCGS,the PCGS aggregate was firstly prepared,and then the influencing factors of the mechanical properties,durability of cement(fly ash)stabilized PCGS and strength improvement measures was researched.And through engineering tests,the key construction technologies of cement(fly ash)stabilized PCGS was proposed at last.Based on the physical and mechanical characteristics of PCGS,the preparation technology of coarse and fine PCGS aggregates were developed,then the mineral composition,physical and mechanical properties,stability,and environmental impact property of PCGS aggregates were studied.The results showed that the volume stability of PCGS aggregates is good,and the leaching concentrations of heavy metals from PCGS aggregates could comply with the limit values set in the identification standard,which indicated it belongs to class Ⅰ general industrial solid waste,so that road base material prepared by PCGS aggregates has little harm to the environment.And the PCGS aggregates has a good gradation and grain type,however compared with crushed stone,its water absorption and crushing value are relatively high.The influence of the rate of PCGS aggregates replacing crushed stone,the crushing value of coarse PCGS aggregates,the gradation of PCGS aggregates,the content and quality of fly ash,and the dosage of cement on the 7-day unconfined compressive strength of cement stabilized PCGS were discussed.The results showed that the 7-day unconfined compressive strength of cement stabilized PCGS is 21%lower than that of cement stabilized crushed stone,and the strength of cement stabilized PCGS decreases with the crushing value of coarse PCGS aggregate increase.The strength of cement stabilized PCGS could be improved by suspension dense type gradation design and adding fly ash.The suitable amount of fly ash is10%～20%.Finally,the 7-day unconfined compressive strength of PCGS with a crushing value of 37.2% stabilized by cement or cement fly ash could reach 6.0 MPa and 7.4 MPa respectively.The long-term mechanical properties,drying shrinkage resistance and frost resistance of cement stabilized PCGS,cement fly ash stabilized PCGS,and cement stabilized crushed stone,were compared.The results showed that under the same cement dosage,the compressive strength,cleavage strength and compression rebound modulus of cement stabilized PCGS are slightly lower than that of cement stabilized crushed stone,and the mechanical properties of cement fly ash stabilized PCGS are basically the same as cement stabilized crushed stone.Due to the internal curing introduced by porous aggregates,the drying shrinkage resistance and frost resistance of cement(fly ash)stabilized PCGS is better than cement stabilized crushed stone.Through engineering tests,the rolling of light vibration was developed,and the results showed that adopting the measure of suspension dense type gradation design and light vibration rolling could avoid PCGS aggregates crushing in the construction process.The follow-up observation results of the test section showed that the cement(fly ash)stabilized PCGS has good drying shrinkage resistance and frost resistance,has significant social and economic benefits,and has good application prospects.