Research On Road Performance Of Desulfurization Ash Stabilized Soil

The output of semi-dry sintering flue gas desulfurization ash（hereinafter referred to as desulfurization ash）is huge and needs to be treated urgently.Realizing its large-scale resource utilization is a research hotspot at present.Considering its certain cementitious activity,its feasibility as a stabilizer in road engineering and preparation of stabilized soil filler was studied.The main research contents and results are as follows:（1）The basic physicochemical properties and the gelling characteristics of desulfurization ash were determined by cement test and microscopic test methods such as SEM,XRD,XRF,and particle size analysis.It is found that desulfurization ash has significant water absorption.The self-harden property is mainly achieved by the dissolution and devitrification process of hemihydrate gypsum,and the hydration product is Ca SO₄·2H₂O.The compressive strength and water resistance of its hardened paste are poor which means it is unsuitable as gelling material alone.It is suggested that the sulphate composition can be mixed with the cement clinker or pozzolanic active substances to prepare cementitious materials.（2）A desulfurization ash cementitious material that meets the performance requirements of expansive cement was invented,and its optimal mixing ratio was 5%.Its compressive strength and linear expansion rate of the desulfurized ash cementitious material were studied by the paste test.The maximum amount of desulfurization ash was 20%when the strength and expansion performance requirements were met.The microscopic mechanism of the strength and expansion performance was determined by the analysis of hydration products.The influence mechanism of ettringite development on material strength and expansion performance was studied.（3）The scheme of desulfurization ash and lime combined to stabilize the soil was proposed.The mechanical properties of lime desulfurization ash stabilized soil were researched by CBR test and unconfined compressive strength test,deciding that the optimal dosage of lime is 6%and the maximum amount of desulfurization ash was 20%when the mechanical properties of expressway subgrade were met.It was found that the strength of lime-stabilized soil can be improved when the amount of desulfurization ash is 5%～10%.The development trend of lime desulfurization ash stable soil strength was studied.The microscopic action mechanism of lime desulfurization ash stabilized soil was researched by the microscopic analysis method,which found that the formation of AFt-C-S-H structure network is the reason for strength growth.（4）The performance of lime desulfurization ash stabilized soil under the water action was studied.The compressive strength at different ages under water-saturation and dry-wet cycle conditions was researched.The effect of the desulfurization ash amount and curing time on its water resistance to water damage was studied.The volume change under water action was investigated by the CBR swelling test in water and the drying shrinkage test.The overall trend and mechanism of the material volume change were studied.Based on its mechanical performance and water resistance,it was proposed that the optimal content is 6%lime+10%desulfurized ash,which can be used for the subbase of expressways and Class I highways.Compared with lime stabilized soil in the same strength level,27577 yuan can be saved and221t desulfurization ash can be consumed per 1000m³,which has significant environmental and economic benefits.