Material Optimization And Effect Evaluation Of Solidifying And Stabilizing Polluted River Sediment In Rural Areas

Cement is often used in traditional solidification stabilization techniques,which leads to high solidification costs.And if the sediment is solidified by cement back to the soil,the sediment has poor environmental friendliness.Exploring locally available,low-cost and environmentally friendly solidified and stabilized materials in rural areas can promote the resource utilization of polluted sediment in rural rivers.Firstly,Mineral materials and cementitious materials with the best curing and stabilization effect were selected in this study.On this basis,single factor and response surface optimization experiments were carried out to explore the optimal mixing ratio of solidified materials.Meanwhile,the mechanism of curing reaction between curing materials and sediment was investigated,and the ecological safety,stability and economic benefit of curing agent were evaluated comprehensively.The main conclusions are as follows:The results of experiments of different flocculants promoting natural drying dehydration of sediment showed that the efficiency of PFS was higher than PAC under the same dosage,and the optimal dosage of PFS was 2.5 g/kg.Mineral materials(dolomite,bentonite,calcium carbonate,quartz sand,slag)and gelling agent materials(citrus peel,pomelo peel,tofu sticks,sweet potato stalk,sodium carboxymethyl cellulose,mulberry leaf,sauce grass,sodium alginate,chicken manure)screening test results showed that the bentonite on the improving compressive strength of solidified soil had the best effect,and the citrus peel had optimal gelling effect.The results of single factor test showed that the strength of solidified soil increased with the increase of cement content.When bentonite content was 5 g/kg and citrus peel content was 10 g/kg,the solidified soil strength could be significantly improved,but excessive dosage would lead to the decrease of solidified soil strength.Response surface optimization showed that the optimal proportion of curing agent was cement 15 g/kg,bentonite 5.14 g/kg,citrus peel 9.66 g/kg.The strength of solidified soil could reach 3144.84 kPa after curing for 28 days at this dosage.XRD and SEM tests were carried out on the solidified soil samples with different solidified materials content ratio.It was found that with the increase of cement content,the solidified soil porosity decreased,the content of fibrous and needle like calcium aluminate hydrate and calcium silicate hydrate increased,and the content of pectin released from citrus peel increased.With the increase of bentonite content,the contents of calcium silicate hydrate and calcium aluminate hydrate increased first and then decreased,and the porosity of solidified soil became larger.With the increase of citrus peel content,the solidified soil porosity gradually became loose from compact,the content of calcium silicate hydrate and calcium aluminate hydrate decreased,and the content of low-ester pectic flocs increased first and then decreased.The content of low-ester pectic flocs was consistent with the change trend of the compressive strength of solidified soil.The results of ecological safety and stability test showed that the leaching concentrations of heavy metals,TN and TP in solidified soil all met the corresponding environmental quality standards.It was found that cement,bentonite and citrus peel were not conducive to germination of ryegrass.The results also showed that bentonite added to the bottom mud could promote the growth of ryegrass.The direct incorporation of citrus peel into the sediment could promote the propagation of pathogenic bacteria in the sediment,which was not conducive to the growth of ryegrass.The results of economic benefit evaluation showed that the incorporation of bentonite and citrus peel not only ensured the strength of solidified soil,but also reduced the cement consumption and cost.