Experimental Study On Mechanical Properties And Durability Of Circulating Fluidized Bed Combustion Fly Ash Based Geopolymer Pisha Sandstone Cement Composite Soil

Pisha sandstone is a special kind of mudstone and siltstone,which is mainly distributed in Ordos Plateau in the border area of Shanxi,Shaanxi and Inner Mongolia.Because of its poor structure and performance,it becomes sediment when it meets water.Therefore,the soil erosion is very serious in rainy season.However,the loose Pisha sandstone can be developed into sandstone cement soil and applied to subgrade cushion,canal lining,etc.,which can not only realize the utilization of resources,but also reduce the extent of soil erosion in the sandstone area of the Yellow River Basin.Because there are many thermal power plants and thermal power companies in Hohhot and Baotou area in Inner Mongolia,and they mostly use circulating fluidized bed boiler coal-fired technology to reduce pollution.Using this kind of technology can produce many combustion fly ash particles,which are coarse and have poor activity and most of them are not effectively utilized as waste materials.Therefore,this thesis takes Pisha sandstone as the main body,and adds some combustion fly ash produced by circulating fluidized bed boiler combustion in thermal power companies to replace cement,the experimental object,and makes CFB combustion fly ash based geopolymer Pisha sandstone cement composite soil.The mechanical properties and microstructure of CFB combustion fly ash based geopolymer Pisha sandstone cement composite soil were observed and analyzed by universal material testing machine,scanning electron microscope,Fourier transform infrared spectroscopy,synchronous thermal analyzer and mercury intrusion meter,and the optimum physicochemical reaction conditions and durability under sulfate attack and freeze-thaw cycle were explored.The main conclusions are as follows:(1)The alkali equivalent and the content of combustion fly ash have great influence on the CFB combustion fly ash based geopolymer Pisha sandstone cement composite soil.The increase of combustion fly ash content will gradually weaken the strength of composite soil.With the increase of alkali equivalent,the strength growth rate of composite soil increases first and then remains basically unchanged.Because of the operability of construction,5% alkali equivalent is selected as the best alkali equivalent.(2)With the increase of alkali excitation temperature,the early strength of CFB combustion fly ash based geopolymer Pisha sandstone cement composite soil can be enhanced.But at 28 days,its porosity increases,entrainment pores increase,and the sample expands and cracks,resulting in obvious decrease in compressive strength.Therefore,the optimum physicochemical reaction temperature of CFB combustion fly ash based geopolymer Pisha sandstone cement composite soil is 20 ℃.(3)With the increase of the days of salt invasion,the strength of CFB combustion fly ash based geopolymer Pisha sandstone cement composite soil decreases.With the increase of freeze-thaw cycles,the frost resistance of the CFB combustion fly ash based geopolymer Pisha sandstone cement composite soil decreased,and the first three freezethaw cycles caused great damage to the internal pores of the composite soil,and the strength decreased most seriously.