Rapid Stabilization Of Highwater Content Muddy Soil With Reactive Mg O Carbonization

Magnesium solidification and carbonization technology is a new environmentally friendly foundation treatment with low carbon emissions.The carbonization research group of Southeast University has carried out systematic research on this technology,but the results are mainly concentrated on soft soil and silty soil.However,there are still ultra-soft soils with higher water content,compressibility and sensitivity.This paper focuses on the rapid carbonization and resource utilization of ultra-soft soil.The regularity and effects of carbonization and construction process were studied through physical and chemical tests,mechanical tests and micro-tests.The main results are as follows:(1)The changes of physical and chemical properties of magnesia carbonized solidified ultra-soft soil were studied.The impacts include carbonization time,MgO content,CO2 pressure and size of carbonized soil particles.Results show that the water content,liquid plastic limit,clay content and p H value of solidified soil decrease with the increase of carbonization time and CO2 pressure.The decrease value of water content,p H and the increase value of pore fluid conductivity before and after carbonization of soil samples increased with the increase of magnesium oxide content.The liquid plastic limit and clay content of soil samples increased with the addition of MgO content.The smaller the sludge particles,the lower the water content,the liquid plastic limit,the clay content,and the p H value.(2)The variation of mechanical properties of magnesia carbonized solidified ultrasoft soil are studied.The results show that with the increase of carbonization time,the compressive strength and shear strength of the solidified soil firstly increase and then decrease.Additionally,compressive strength and shear strength increase with the increase of MgO content,decrease with the increase of carbonization pressure and sludge particles.(3)The effectiveness of adding calcium carbide residue into the carbonized solidified silt is analyzed.Under the condition of low magnesia content,the engineering properties of silt can be effectively improved by adding calcium carbide residue.In addtion there is an optimal range of content.For 10% magnesia content of carbonated solidified soil,the content of calcium carbide slag should be controlled between 5%and 10%.(4)The mechanism of rapid carbonization and solidification ultra-soft soil is revealed by microscopic test analysis.Main carbide products are nesquehonite,hydromagnesite and dypingite.With the increase of carbonization products,the chemical cementation and filling compaction of the carbonized products become stronger.Meanwhile,the compactness of the soil is also positively correlated with carbonization time,carbonization pressure,and magnesium oxide content.(5)Based on laboratory tests,reasonable construction parameters of carbonization and solidification of ultra-soft soil are summarized,and field construction technology of MgO carbonization and solidification of ultra-soft soil is preliminarily proposed.