Study On Mechanism And Performance Of The Coastal Saline Soil Cured By Slag Composite Curing Agent

Coastal saline soil has some engineering characteristics, such as salt expansion, collapsibility, corrosivity and hygroscopic softening, because it contains a lot of soluble salts. The engineering construction involves the problem of saline soil curing in the coastal area. Due to the high cost of the conventional curing methods and poor results in many aspects, there is an urgent need for a new curing agent to ensure engineering safety and reasonable investment.On the basis of comprehensive analysis of Caofeidian coastal saline soil and slag material in macrostructure and microstructure characteristics and chemical properties, the technical idea that the slag composite curing agent was used to cure the coastal saline soil was presented, and performance requirements of the slag composite curing agent was determined. Through the unconfined compressive strength test, water stability test, soluble ions content test, SEM analysis, EDS energy analysis and XRD analysis, the unconfined compressive strength, water stability, soluble ions content of cured soil, durability, collapsibility and salt expansion were tested. The microstructure of cured soil was observed, the hydration products of cured soil was analyzed, the curing mechanism of saline soil cured by the slag composite curing agent was clarified. The results show that the unconfined compressive strength of the coastal saline soil cured by the slag composite curing agent are relatively higher, the water stability is relatively better, the durability is relatively better, the anti-collapsibility is relatively better, the anti-salt expansion is also relatively better than cement-soil, and can meet the requirements for the general engineering foundation curation processing. The soluble Cl" ion, SO42-ion and Na+in saline soil take part in the hydration reaction of slag composite curing agent, and the crystals of3CaO·Al2O3·(0.5CaCl2·0.5CaSO4)·12H2O in the shape of lamella and needle are generated, the by-product of NaOH provides stronger alkaline slag environment for slag, the zeolites materials of0.8CaO·0.2Na2O·Al203·3Si02·6H20are generated, thereby the soluble Cl-ion, SO42-ion and Na+ion content in the cured soil are reduced. Through the three degree curing effects on the coastal saline soil cured by the slag composite curing agent, the unconfined compressive strength, water stability, anti-collapsibility and anti-salt expansion of cured soil are improved, and some potential hazards of saline soil are solved. The cured coastal saline soil in seawater can generate compact hard CaCO3shell, with the growth of age, the shell is thicker. The CaCO3crystals are stable and don’t react with other ions in seawater, thereby not only prevent seawater erosion, but also prevent the Ca(OH)2to dissolve erosion, which is the fundamental reason that the slag composite curing agent has good anti-seawater corrosion performance.The optimal ratio of slag composite curing agent is that slag is75%, lime is7.5%, gypsum is7.5%, magnesite is10%. It’s main component is the slag, the cost is60%-70%of cement. The slag composite curing agent is a kind of environmental protection type curing agent.