Research On The Development Of Multi-solid Waste-based Soil Curing Agents And Its Performance In Curing Silty Sandy Soil

In China’s northeast,north and northwest areas are widely distributed in a variety of silty sandy soils.The silty sandy soil has the disadvantages of easy loosening and hard compaction,easy disintegration in water,etc.When filling the roadbed,it is easy to sink,deformation,spalling,erosion and overall instability of the slope surface of the roadbed,road cracking and other diseases,which seriously affect the performance of the road.The cement and lime curing chalk soil has good strength,water stability and frost resistance,and the filled roadbed has high stability and durability.However,the shrinkage of cement-cured chalk soil is large and the risk of cracking is high;the early strength of lime cured chalk soil is low and the later strength develops slowly.Lime and cement production consumes a largeamount of resources and energy,and has high carbon emissions.Based on this,this study used industrial solid wastes such as calcium carbide slag and fly ash,which are widely distributed in the alluvial plain area of the Yellow River in Shandong Province,and then used for curing chalk soil after multiple compounding,and studied the fitting ratio of multiple solid abandonment soil curing agent by orthogonal test method,and studied the mechanical properties and durability performance of cured chalk soil,clarified the influence mechanism of the curing agent fitting ratio of chalk soil,proposed the suitable curing agent for different soil texture The road performance of cured soils under different factors such as the amount of curing agent,compaction degree and water content were investigated,and the hydration products of cured soils were revealed by microscopic means.The main research contents and conclusions are as follows:(1)Two typical silty soils in the alluvial plain area of the Yellow River in Shandong Province:low liquid limit powder soil and silty sand were selected for geotechnical tests,and the test results showed that the liquid limit of silty sand was 22.9%,the plasticity index was 9.3,and the corresponding CBR values were 5.4%,4.8%and 4.5%at compaction degrees of 96%,95%and 94%;the liquid limit of low liquid limit powder soil was 28.9%,the plasticity index was 5.9,and the corresponding CBR values are 4.1%,3.8%and 3.6%for 96%,95%and 94%compaction;it cannot meet the requirements of the upper roadbed filling as stipulated in the Specification for Design of Highway Roadbed.(2)Based on the orthogonal test method to study the curing agent ratio,three factors were selected,namely,cement dosing,slag to fly ash ratio and powder(Na2SO4)dosing,and three test levels were designed for each factor,and the orthogonal test results showed that:for silty sand,the main order of influence of each factor was cement dosing>slag to powder ratio>powder dosing,combined with 7d unconfined compressive strength and economic The ratio of cement:calcium carbide slag:fly ash:yuanming powder=30%:40.80%:27.20%:2%;for low liquid limit powder soil,the order of influence of each factor is slag to powder ratio>cement dosing>yuanming powder dosing,combined with 7d lateral limit compressive strength and economic factors,the ratio of cement:calcium carbide slag:fly ash:yuanming powder=30%:13.60%:54.40%:2%:54.40%:2%.(3)To study the effects of the variation of curing agent admixture(4%,6%,8%,10%,12%,14%,16%),compaction(98%,96%,94%,92%,90%)and moisture content(-3%,-1.5%,0%,1.5%,3%)on the CBR,unconfined compressive strength and splitting strength of the two cured soils with the age of curing(3d,7d,28d,56d,90d,180d)to further reveal the relationship between unconfined compressive strength and CBR.The results showed that the CBR.unconfined compressive strength and splitting strength of the silty sand cured soil increased and then decreased with the increase of the curing agent,and the mechanical properties of the 10%cured soil performed the best;the CBR,unconfined compressive strength and splitting strength of the low liquid limit powder soil cured soil increased with the increase of the mixing amount.The CBR,unconfined compressive strength and splitting strength of both cured soils increased with the increase of curing age and decreased with the decrease of compaction;with the increase of initial water content,the CBR value showed a trend of increasing and then decreasing,and the CBR value was highest at the optimum water content.The CBR of cured soil showed a positive correlation with the unconfined compressive strength.Curing agent dose≥1%of curing silty sand and curing agent dose≥5%of curing low liquid limit silty soil can meet the specification of the filling requirements of the upper roadbed;curing agent dose≥8%of curing silty sand can meet the specification of the strength requirements of the subgrade.(4)Study the compaction degree of 96%when the two curing soil water stability performance,dry shrinkage performance,frost resistance with the amount of curing agent(6%,8%,10%/4%,10%,16%)changes in the law.The results show that:the water stability coefficient of cured silty sand are≥90%;and dry shrinkage strain and water loss rate in the early growth rate.7d after the gradual leveling off;maintenance 28d curing soil freeze-thaw cycle 5 times the frost resistance index are≥ 70%,curing agent dosing 8%,10%,12%of the curing soil in line with the five cycles under the mass loss rate of not more than 5%of the requirements.Curing low liquid limit powder soil water stability coefficient are≥ 80%;maintenance 28d curing soil freeze-thaw cycle 5 times the frost index are≥ 60%,curing agent dosing≥ 14%of the curing soil to meet the requirements of 5 times under the cycle of quality loss rate of not more than 5%.The water stability coefficient,dry shrinkage strain and frost index of the two cured soils increased with the amount of curing agent and the age of the increase.