Study On Frost Resistance And Wave Velocity Of Fiber/Cement Modified Building Slurry

A large amount of waste slurry is produced in the course of construction.At present,the disposal of construction waste slurry is characterized by serious pollution and poor economy.Therefore,it is of great significance to develop an effective modification method,reveal its curing mechanism and master the Mechanical Properties of the modified slurry for the recycling of waste slurry.The study of wave velocity characteristics can improve the traditional test method of compressive strength of modified slurry,and the physical indexes under multiple freeze-thaw cycles are important to reveal the improvement effect of cement / fiber modified slurry.The main work and achievements are as follows:(1)Analyzing the influence of 10%,15%,20%,25%,30% cement content on the compressive strength of the modified slurry with cement ratio.When the cement content is 25%,the strength increase is the biggest,and when the cement content is 20%,the strength increase is 44%.The 28 dcompressive strength of the modified slurry with 20% cement content can meet the requirement of this material as embankment filling material.On the basis of 20% cement blending ratio,0.25%,0.5%,0.75% and 1% polypropylene fibers were added.The unconfined compressive strength of fiber / cement modified slurry at the ages of 7d and 28 d was studied.Compared with the compressive strength and age effect,it is found that 0.75% fiber blending ratio can make the best performance of fiber / cement modified slurry.(2)The relationship between compressive strength and wave velocity of fiber / cement modified slurry shows that the wave velocity does not change with the increase of age.In the case of no fiber,the wave velocity increases with the increase of cement content.Under the condition of constant cement content,the wave velocity decreases with the increase of fiber content.The mathematical model of unconfined compressive strength and ultrasonic wave velocity Vs is established,and the average relative error is less than 25%.(3)On the basis of cement blending ratio of 20%,0.25%,0.5%,0.75% and 1% polypropylene fibers were added.It is found that with the increase of fiber content,the decrease of strength in the early stage of freeze-thaw cycle is slowed down.In the late stage of freeze-thaw cycle,0.75% fiber content had the most obvious effect,and in the 10 th freeze-thaw cycle,the strength of the modified slurry had the biggest increase.Based on Meso-random damage mec,a two-stage freeze-thaw damage model is established.The error is within the variance of the mean stress plus or minus one time.(4)Microcosmic tests were carried out on the damaged fiber / cement modified slurry samples after freeze-thaw cycles,and the SEM images were compared with the mean curve of freeze-thaw damage evolution,the change rule of microstructure of the specimen after freeze-thaw cycles is basically consistent with the damage development rule reflected by the damage evolution mean curve,which can reveal the damage principle of freeze-thaw cycles at the micro level.