Research On Strength Deterioration Mechanism And Salt Resistance Solidification Technology Of Coastal Soft Soil Cement Soil

Coastal soft soil contains a large number of corrosive salts,such as sulfate,magnesium salt and chloride salt,and its soft soil curing project will inevitably encounter ion corrosion problems,which will cause deterioration effect of cement soil,which in turn leads to the destruction of cement soil structure and reduction of strength.In this thesis,the physical and mechanical properties and microscopic structural components of coastal soft soil cement soil were studied at different corrosion ions,different concentrations and different curing ages,and the deterioration mechanism of coastal soft soil cement soil in ionic corrosion environment was analyzed,and the optimal amount of salt-resistant materials was studied by orthogonal test.The results obtained provide a reference for the application of coastal soft soil curing engineering,and finally,blast furnace slag and fly ash are selected as salt-resistant curing materials for verification.（1）Summarize and analyze the ion content and mechanism of action in seawater,and provide reference for the preparation of corrosion environment and the analysis of test results.The F’s salt formed by Cl^-reaction hinders the hard coagulation reaction,the gypsum dihydrate and AFt generated by SO₄^2-reaction have swelling properties,and the Mg（OH）₂,M-S-H and M-A-H produced by Mg²⁺reaction have loose structure and low strength.The main corrosion ions in seawater were determined to be Cl^-,Mg²⁺and SO₄^2-,with concentrations of 6%,0.1%and 0.2%,respectively.On this basis,relevant tests are designed,including ionic corrosion orthogonal test and single-ion solution corrosion related test.（2）Tests related to ionic corrosion orthogonal tests and single-ion solution corrosion are carried out.During the 28d curing period,SO₄^2-had the greatest effect on the weakening of compressive strength of cement soil,followed by Mg²⁺,and Cl^-played a role in enhancing it.With the increase of concentration,SO₄^2-and Cl^-enhanced the quality change rate of cement soil,and Mg²⁺first enhanced and then weakened the quality change of cement soil,with an inflection point of 0.2%.The cement soil cured by 6%Cl^-solution has a role in enhancing the compressive strength of cement before60 days and weakening the compressive strength of cement soil after 60 days.The compressive strength of cement soil cured by 0.4%Mg²⁺solution and 0.8%SO₄^2-solution decreased with age,and the long-term weakening effect of Mg²⁺was greater than that of SO₄^2-.（3）With the increase of Cl^-solution concentration and curing age,the formation of F’s salt also increases,when the amount of formation is small,the structure of cement soil can be strengthened,no cracks are found on meso,and the structural integrity of cement soil is destroyed when the amount of formation is large.With the increase of the concentration and age of Mg²⁺solution,the amount of C-A-H,C-S-H consumed and the resulting M-A-H,M-S-H and Mg（OH）₂ also increased,resulting in the loss of cementation between soil particles,the destruction of cement-soil structure,and the evolution of cracks on the surface of cement-soil into crack-like structures.With the increase of SO₄^2-solution concentration and age,the amount of C-A-H consumed and gypsum dihydrate and AFt generated is more,and when the expansion force of the product is greater than the cementation force between the clay particles,the cement-soil structure is damaged,and the surface cracks of the cement soil evolve into concentric circle structure.（4）According to the analysis of the salt curing mechanism of cement soil,Si O₂and Al₂O₃ were determined to be salt resistant curing components,and the arrangement of the unconfined compressive strength of solidified soil with different amounts of Si O₂was:Unconfined compressive strength of solidified soil with 2%dosage>Unconfined compressive strength of solidified soil with 1%dosage>Unconfined compressive strength of solidified soil with 0.5%dosage;The arrangement of the unconfined compressive strength of Al₂O₃ cured soil with different dosages is:Unconfined compressive strength of solidified soil with 1%dosage>Unconfined compressive strength of solidified soil with 2%dosage>Unconfined compressive strength of solidified soil with 0.5%dosage,according to the composition content to determine the optimal content of blast furnace slag and fly ash,and carry out salt curing test application research,the research results prove that salt resistant curing materials are very effective.The thesis has 51 figures,30 tables,and 80 references.