Experimental study on the combined effect of MgO and MICP for reinforcing silt
Specific microorganisms are utilized to decompose urea and produce carbonate ions by microbial induced calcite deposition(MICP)technology,which combines with calcium ions to deposit and form calcium carbonate for reinforcing soil.MICP has advantages such as environmental friendliness and flexible usage compared to traditional chemical methods,but there exist disadvantages such as more treatment steps and unstable reinforcement effects.As a low-carbon technology,active MgO carbonization is applied in the reinforcing soil.CO2 required for MgO carbonization is provided by MICP reaction.Thus,active MgO was combined with MICP to further improve the reinforcement effect in this study.Experimental research on the combined effect of MgO and MICP to reinforce silt was carried out.The results show that the pH of solution is increased by adding MgO,which decreases the hydrolysis rate of urea.The amount of carbonate generated when replacing CaCl2 with MgO is lower than when using CaCl2.The reinforcement tests of silt show that the sample disintegration rate can be reduced effectively by mixing MgO into soil and conducting MICP treatment,which improves the unconfined compressive strength.The reinforce effect is better when is at high activity MgO content.The reinforced strength is linear positive correlated with the MgO content when it is in the range of 5％to 20％.Compared to the samples treated by pure MICP or by mixing only MgO in silt,higher strength is provided by the combined effect of MgO and MICP,which reduces process steps.XRD test shows that a considerable amount of basic magnesium carbonate is generated in the combined reinforced sample,indicating that sufficient carbonization reaction occurs.The microscopic test results indicate that large amounts of petal or sheet basic magnesium carbonate are generated in the sample reinforced by MgO and MICP,which are widely distributed in the gap and on the surface of particles,enhancing cementation effect.The common problem of uneven reinforcement when using only MICP treatment can be effectively improved by the combination of MgO and MICP method.
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