Experimental Study On The Effect Of Ultra-fine Cement On The Engineering Properties Of Humic Acid Containing Cemented Soil

Cement is the main building material,and all aspects of national economic construction are inseparable from cement.Currently,China has the largest cement production,accounting for more than half of the world’s total cement production.However,the environmental impact of cement production must be considered.The CO₂ emitted by the cement industry accounts for about 1/4 of the global industrial carbon emissions.To achieve China’s carbon peaking and carbon neutrality goals,reducing cement consumption has practical significance for CO₂ emission reduction.Peat soil is widely distributed in the Dianchi Lake area,and cemented soil mixing method is often used in engineering to treat peat soil foundation.The cemented soil mixing method will use a large amount of cement,and the reinforcement effect will be affected by multiple factors.Peat soil is a special soft soil composed of humic acid,soil inorganic matter,and animal and plant residues.It has high organic matter content,high water content,low bearing capacity,large void ratio,low permeability,and high compressibility.The presence of humic acid will affect the reinforcement effect of the cemented soil mixing method.As one of the important components of peat soil humic acid,humic acid has a stronger effect on cement soil than other components.In recent years,the research has been mainly on the law of the influence of humic acid on cement soil,and the research on environmental protection needs to be more extensive.Ultra-fine cement has better performance than ordinary Portland cement and has no additional pollution compared to other additives and materials.This paper studies the influence of ultra-fine cement on the engineering shape of cemented soil containing humic acid and explores how to reduce the amount of cement under the condition of meeting the actual demand,which is of great significance to engineering applications.To sum up,this paper uses indoor experiments to simulate peat soil by adding humic acid to alluvial and diluvial cohesive soil and adding ultra-fine cement to ordinary Portland cement in a certain proportion to form a composite cement curing agent for reinforcement.In conclusion,this paper uses indoor experiments to simulate peat soil by adding humic acid to alluvial and diluvial cohesive soil and adding ultra-fine cement to ordinary Portland cement in a certain proportion to form a composite cement curing agent for reinforcement.The effect of ultra-fine cement on the strength of cemented soil containing humic acid is studied by mechanical tests.The effect of ultra-fine cement on the micro-pore structure of humic acid-containing cemented soil is explored using a micro-pore structure test.This study reveals the reinforcement mechanism of ultra-fine cement to cemented soil containing humic acid.The main research contents are as follows:（1）The unconfined compressive strength test is used to study the effect of ultra-fine cement on the strength of humic acid-containing cemented soil.The test results show that the effect of humic acid on cemented soil is not only to"delay"the hydration reaction of cement.The interaction between humic acid and hydration reaction makes the microscopic pore structure of the sample loose and open.The ultra-fine cement in the composite cement curing agent can improve the strength of the humic acid-containing cemented soil.The strengthening effect of ultra-fine cement is more evident in an environment with higher humic acid content.Taking the immersion time of 90days as an example,when the proportion of ultrafine cement is 10%～50%,the unconfined compressive strength of the sample is 7.42%～47.54%higher than that without ultrafine cement.It is practical and economical when the proportion of superfine cement in the composite cement curing agent is 10%.（2）The effect of ultra-fine cement on the micro-pore structure of cement-soil containing humic acid is studied by mercury intrusion test,scanning electron microscope test,and PCAS micro-quantitative testing technology.The proportion of large pores（pore diameter>10μm）in the sample decreases significantly when the proportion of ultrafine cement increases from 0%to30%,reduced by about 28.12%.The microscopic pore structure gradually improves with the increase of the proportion of ultra-fine cement,and the pores gradually change from fibrous filling to cemented filling.Agglomerates combine to form a unit body,and the connectivity of the unit body is enhanced.The aggregates are combined to form a structural element,and the combination of the structural element is enhanced.The results of the PCAS micro-quantitative test technology and mercury porosimetry test have good consistency,but there are certain differences in the scope of application and function of the two.（3）The effect of ultra-fine cement on the composition of humic acid-containing cemented soil is studied using an X-ray powder diffraction test.The results show that the increase in the proportion of ultrafine cement makes the relative content of hydration products in the sample gradually increase.The pore volume affects the relative content of hydration products,so the increase is not obvious.The comprehensive test results show that the composite cement curing agent composed of superfine cement and ordinary Portland cement can improve the microscopic pore structure and unconfined compressive strength of humic acid-containing cemented soil.The increase in the proportion of ultra-fine cement makes the microscopic pore structure of humic acid-containing cemented soil gradually become denser from loose and open.The addition of ultra-fine cement weakened the effect of humic acid on cemented soil,and the strength of humic acid-cemented soil containing increased.The composite cement curing agent composed of ultra-fine cement with a proportion of 10%and ordinary portland cement has a better effect on the reinforcement of peat soil with high humic acid content.In-depth research can be done in combination with the conclusions of this study to realize the reinforcement of peat soil foundation and reduce the amount of cement and provide a theoretical basis for reducing CO₂ emissions and environmental protection.