Properties Of Sludge Solidified With Soda Residue As Landfill Covering Material Under The Action Of Environmental Factors

In recent years,with the rapid increase of sludge production,the traditional treatment methods with low efficiency and backwardness have been eliminated,and the sludge treatment is developing towards "reduction,resource and harmless".In this context,considering the needs of landfill for covering materials,it is studied to use the solidified sludge as the intermediate and final covering materials for landfills.However,long-term exposure of intermediate and final covers to air will be affected by environmental factors(such as temperature,water,etc.)and their properties will change.At present,the research in this area needs to be improved.Therefore,Sewage sludge was solidified soda residue,ground granulated blast furnace slag and quick lime.Conducted microstructure and mechanical properties of solidified sludge under dry-wet,freeze-thaw cycles and simulated rainfall,and analysis of the variation characteristics of the solidified sludge micro and macro properties under environmental factors.It provides theoretical support for the application of solidified sludge as intermediate and final landfill cover materials.The main contents of this paper and the conclusions drawn are as follows:(1)An investigation of the intensity and microscopic tests of solidified sludge under the dry-wet cycles was conducted.The results showed that the unconfined compressive strength of the cured sludge increased when the number of wet and dry cycles increased,and the intensity was reduced slightly in the 7th wet and dry cycle,but was higher than the initial intensity before cycles.The sustained hydration reaction between solidifiers and sludge helps to improve the dry-wet durability of the solidified sludge.(2)An investigation of the intensity and microscopic tests of solidified sludge under the freeze-thaw cycles was conducted.The results showed that with the increase of the number of freeze-thaw cycles,the unconfined compressive strength of the solidified sludge increased at first and then decreased.After 10 freeze-thaw cycles,the intensity was higher than the initial intensity before cycles.The frost swell and large-dimension ettringite formation leaded to enlargement of the pores,but the continuation of the hydration reaction between solidifiers and sludge helps to maintain the structural compactness and improve the freeze-thaw durability of the solidified sludge.(3)An experimental study on the macroscopic characteristics of solidified sludge under the rainfall was conducted.The results show that: The solidified sludge was greatly affected at the initial stage of rainfall.After 24 hours of continuous rainfall,there was soil particle exfoliation on the surface of the sample,but the unconfined compressive strength was still greater than the initial strength,and the rain erosion resistance was good.(4)According to the good strength properties of soda residue-ground granulated blast furnace slag-quick lime cured sludge under the action of environmental factors,the cured sludge can be used as intermediate cover and closure cover material for landfills.