Unconstrained Compression Test And Time Effect Of Fiber/cement Modified Building Slurry

Slurry is a common engineering auxiliary construction material,which is widely used in bored piles,shield tunneling and other construction.Therefore,a lot of waste slurry is produced.If these waste slurry is not treated,it will cause a series of problems,such as environmental pollution.Therefore,in practical engineering,it is necessary to find a low-cost recycling method.Cement,as a common chemical curing agent,has been widely used in engineering construction at home and abroad.It has high application value for slurry modification.As a new kind of admixture,polypropylene fibers have the effect of reinforcing and toughening cement soil,and can strengthen its crack resistance.The two materials were studied to get the improvement effect on slurry.Therefore,it is of great engineering value and reference significance to study the mechanical properties and microstructure of cement modified slurry?CMS?and fiber cement modified slurry?FCMS?.To this end,the main research work and achievements of this paper are as follows:?1?The unconfined compression test is divided into two groups:one is CMS,the other is FCMS.The curing age of CMS group was set as 8 age periods,7 days,14 days,28 days,56 days,90 days,120 days,150 days and 180 days respectively.Five cement dosages were set for each age period,5%,10%,15%,20%,25%respectively.The curing age of FCMS group was also set as 8age periods,7 days,14 days,28 days,56 days,90 days,120 days,150 days and 180 days,respectively.The cement dosage was set as 20%,and five fiber dosage was set as 20%for each age period.0%,0.25%,0.5%,0.75%and 1%respectively.The unconfined compressive tests of the two groups of modified slurrys show that the unconfined compressive strength of CMS increases linearly with the cement mixing ratio;for unconfined compressive tests,the optimal cement mixing ratio is in the range of 20%-25%,and the unconfined compressive strength of FCMS increases linearly with the increase of fiber content,then decreases slightly;for UCS,polypropylene fibers increase linearly at first,and then decrease slightly.The optimum dimension incorporation ratio is0.75%.Through the unconfined compressive tests of CMS and FCMS with different curing time,it is found that the unconfined compressive strength increases sharply at first and then tends to remain unchanged with the increase of curing time.?2?The stress-strain curve??-??,stress-cement blending curve??-A_w?,stress-fiber blending curve(?-A_wf)stress-curing age curve??-T?are drawn from the test data of UCS,and the characteristics of these curves are analyzed.The corresponding compressive strength increases 9.8times when the curing age of CMS is 7 days and the cement content increases from 5%to 25%,and the curing age increases from 7 days to 18 days.At 0 d,the increase ratio decreased to 4.7 times.When the curing age of FCMS is 7 days and the content of fibers increases from 0.25%to 1%,the compressive strength of FCMS increases by 10%-28%compared with that of FCMS without fibers.The rule of change is the same from 7 days to 90 days.The compressive strength of FCMS increases first and then decreases slightly with the increase of the content of fibers from 90 days to180 days.With the increase of curing age,the unconfined compressive strength of CMS with 5%and 25%cement content increased by about 2.5 times on average from 7d to 180d.The unconfined compressive strength of FCMS with 0%and 1%fibers increased about 1.2 times on average from 7days to 180 days.?3?According to the mathematical characteristics of?-???-A_w??-A_wfand?-T curves,the stress-strain curve model?MTH model?,stress-age model,stress-cement-fiber content model,unconfined compressive strength model are constructed.In order to study the influence of modified materials on the model parameters,the dosage factors A_wand A_wfare introduced to determine the new materials according to the actual engineering dosage.?4?The microstructure of FCMS and CMS was analyzed by SEM,EDX and XRD.Microscopic test results show that the increase of cement,fiber content and curing age can make the overall structure of slurry more compact.Macroscopic mechanical properties are explained by microscopic mechanism.