Research On Engineering Behavior And Microstructure Of Humic Acid On Cement Soil

Strengthening peat soil foundation is a common problem in engineering,and cement is one of the most commonly used curing agents.However,when strengthening peat soil with high organic matter content,the organic matter in soil will lead to unsatisfactory reinforcement effect.Scholars believe that humic acid in peat soil can reduce the hydration products of cement by hindering the hydration reaction of cement,thus weakening the reinforcement effect of cement.However,different components of organic matter have different effects on the reinforcement effect of cement,and have not been paid enough attention to,Therefore,this paper deeply studies the effect of humic acid in organic matter on cement reinforcement effect and its mechanism.In this paper,the method of adding humic acid to the air dried alluvial proluvial cohesive soil is used to simulate the peat soil with different organic matter content.Taking cement as the only curing agent,the influence of humic acid on the engineering properties of cement soil and its mechanism are studied through the indoor unconfined compressive strength test,combined with the test results of scanning electron microscope,X-ray diffraction and mercury intrusion test.Through the above experimental study,the following conclusions are obtained:(1)Through the unconfined compressive strength test to study the influence of humic acid on the strength of cement soil,it is found that the existence of humic acid will make the strength of cement soil decrease obviously,and its strength gradually decreases with the increase of humic acid content;With the increase of curing age,the strength of cement soil first increases to the peak value and then decreases;The negative effect of humic acid in cement soil can be reduced by increasing the ratio of cement to soil.(2)The influence mechanism of humic acid on the strength of cement soil was studied by scanning electron microscope,X-ray diffraction and mercury intrusion test.SEM images of cement soil mixed with humic acid show that the internal pore structure of cement soil is obvious,and the uniformity of cement soil itself and the cementation between cement soil particles are weakened;With the increase of cement mixing ratio,the influence of humic acid gradually decreases,the pores in cement soil are gradually filled by hydration products of cement,and the cementation between cement soil particles increases;In the analysis of X-ray diffraction test results of cement soil mixed with humic acid,it is found that the presence of humic acid in cement soil will weaken the hydration reaction of cement.When the cement ratio is low,the total amount of calcium silicate hydrate and calcium aluminate hydrate in cement soil is low.With the gradual increase of cement addition,the total amount of calcium silicate hydrate and calcium aluminate hydrate in cement soil begins to increase,The test results also show that the total amount of calcium silicate hydrate and calcium aluminate hydrate has a good positive correlation with the strength of cement soil;In the analysis of mercury intrusion test results of cement soil mixed with humic acid,it is found that the total volume of pores in cement soil decreases slightly with the increase of cement mixing ratio.The main reason for this phenomenon is that the hydration products of cement in cement soil gradually fill the pores in cement soil,and the pore diameter which has a great influence on the strength of cement soil is mainly concentrated in 10 nm ～ 60 NM Between 1000-3000 nm and 6000-40000 nm;With the increase of cement content in cement soil,the influence of humic acid can be weakened appropriately,but the influence of humic acid can not be completely eliminated.