| At present,ordinary Portland cement（OPC）solidified soil has some shortcomings,such as low early strength and poor corrosion resistance,making it difficult to meet the requirements of foundation treatment under certain specific conditions.My country’s self-developed calcium sulphoaluminate cement（CSA）has the advantages of fast setting,high early strength,strong corrosion resistance,and low carbon emissions during manufacturing.Its characteristics can be used to deal with the defects of OPC solidified soil to solve the problem of poor OPC reinforcement effect.In addition,the organic matter in the sludge will have a greater impact on the cement curing effect.Therefore,this article mainly conducts a systematic study on the organic silt soil solidified by the CSA-OPC composite system through macroscopic and microscopic experiments.Firstly,through the unconfined compressive strength test,the effect of different content of fulvic acid（FA）on the macroscopic physical and mechanical properties of CSA-OPC composite system mortar 3d,7d,28d with different mixing ratios was studied.Analyze the influence of FA on the compressive strength of CSA-OPC composite system mortar,and then determine the optimal curing effect ratio,Study on the phase composition of CSA-OPC composite system samples of different ages and mixing ratios by XRD and TG.Observe the microstructure morphology of the sample by SEM,and MIP was used to characterize the pore structure of the CSA-OPC composite system at different ages with different FA content of 25%and 75%OPC content.The test results show that the unconfined compressive strength of the CSA-OPC composite system shows a downward trend with the increase of FA content.The microscopic mechanism is that FA has an obvious hindering effect on the C3S hydration of OPC,for CSA,FA promoted the production of AFt but changed its shape.Then by adding 0%,0.5%,1%,1.5%,2%FA to the microsilica powder to simulate the silt soil with different organic content,and use CSA-OPC composite system with different mix ratios for reinforcement.The macro-physical and mechanical laws of solidified soil samples of different ages and mix ratios are studied through unconfined compressive strength tests.XRD has been used to study its phase composition law.In this way,we analyze the solidification mechanism of CSA-OPC composite system solidified organic soil,and explore the relationship between the macroscopic physical and mechanical properties and microstructure of solidified soil.The test results show that the unconfined compressive strength of CSA-OPC composite system solidified soil shows a decreasing trend with the increase of FA content,and the greater the OPC content,the worse the solidification effect.Finally,in the silt soil with 2%FA content,add different content of steel slag（SS）and calcium oxide（Ca O）for pretreatment,and then use CSA and OPC for reinforcement,and through the unconfined compressive strength test and stress-strain curve to study the macroscopic physical and mechanical laws,and carry out p H test,XRD to study the change rule of sample p H value and phase composition.The test results show that after pretreatment of SS and Ca O,it has a promoting effect on the hydration of CSA,but does not produce a greater effect on the hydration of OPC,indicating that 2%FA has a greater impact on the hydration of OPC. |
