Research On Strength Properties And Microstructure Of Phosphogypsum Stabilized Soil

The red clay,as a poor soil,it usually cannot be directly used as a highway filling material.Instead,the red clay must be improved to use in highway construction;Phosphogypsum as industrial waste,if phosphogypsum can be added into the red clay as an ameliorant for road construction,the strength of red clay can be improved while a large amount of phosphogypsum can be used to improve the engineering characteristics of red clay.Papers in guiyang acquisition of red clay as the research object,through the strength of the indoor test and microstructure analysis,studied the different content of phosphorus gypsum and cement content on the red clay fluid,plastic limit,the compaction characteristics,the influence of by phosphogypsum unconfined strength of red clay,water stability,shear strength,CBR characteristics research and research in SEM,XRD,microstructure.The optimal ratio of phosphogypsum stabilized red clay is put forward.The main research conclusions are as follows:(1)According to Article 3.3.3.4 of "Code for Design of Highway Subgrade",fine grain soil with liquid limit greater than 50% and plastic index greater than 26 cannot be directly used as embankment filler.The liquid limit and plastic index of phosphogypsum stabilized red clay mixture meet the requirements of the code and can be directly used as embankment filler.(2)According to the maximum dry density,the mass ratio of cement to phosphogypsum is recommended to be 1:2.25-1:3,and the mass ratio of cement to phosphogypsum is recommended to be 1:2.25-1:2.5 according to the unconfined compressive strength.Combined with the test results,it is suggested that the mass ratio of cement to phosphogypsum is 1:2.25-1:2.5 in phosphogypsum cement stabilized soil.(3)With the increase of cement and phosphogypsum content,the cohesion of phosphogypsum stabilized red clay increased first and then decreased slowly,the internal friction Angle gradually increased,the shear strength gradually increased,and the failure form of the mixture was strong softening type.(4)CBR value of mixture increases gradually with the increase of phosphogypsum and cement content.(5)It is found that the water stability of the sample can be effectively improved by adding 15% sodium silicate alone or by using silicification method to reinforce the mixture.(6)When phosphogypsum and cement solidify red clay,the needle-like structure Ca SO3 is produced to fill in the pores,and the hydrated calcium silicate cementitious substance plays a cementing role.At the same time,the needle-like structure can produce an effect similar to reinforcement,which improves the integrity of the mixture,compacts the mixture and improves its strength.