Laboratory Test For Physical And Mechanical Properties Of Modified Cement-Bentonite Material

Cemement-Bentonite(C-B)materials are used to construct slurry trench cut-off walls,which are installed in the subsurface to control movement of groundwater and contaminants and can be particularly useful in decreasing permeability of strata with permeability coefficients overlying an impermeable stratum.The advantages of slurry trench cut-off walls such as convenient construction,lower cost make them widely used in European Countries.This study mainly focuses on two aspects.First,mechanical properties of C-B materials with different types of proportions and curing periods.UCS(unconfined compressive strength)text and TCS(triaxial compressive strength)test are used to acquire mechanical properties such as Failure Strains and Stresses,Cohesion and Internal Friction Angle.Second,change of water content and UCS during change of external environment(humidity and temperature)were measured.Results from strength tests show that shear strength of C-B material were largely increased when cement material is partly repleased by GGBS.However,PFA has no assist to improvement of shear strength of C-B material.TCS tests indicate that cohesion can be significantly increased when GGBS mixed during creation of C-B materials.Both GGBS and PFA show less influence to augment of faiure strain.C-B materials with different curing periods and material compositions show various water content behaviour.Longer curing period does benefit to increase water content stability of C-B samples.C-B samples containing GGBS present best water content stability when comparing with C-B sample including PFA and cement only.Thus,water content stability can be improved by GGBS.However,there is no evidence to support that PFA has positive of negative effect on change of water content stability of C-B samples.C-B materials shows resitance to cold environment.No obvious decrease of UCS were detected for C-B samples without GGBS after 10 times freezing(-5℃)-thawing(10℃)cycles.However,GGBS do harm to maintain the strength of C-B material under freezing(-5℃)-thawing(10℃)cycle.Strength decrease of 61.65%and 35.10%were measured for C-B materials with GGBS included...