Expansive Soil Stabilization By Bagasse Ash Partial Replacement Of Cement

The present research studied the effects using bagasse ash as a partial substitution of Ordinary Portland Cement(OPC)to enhance the geotechnical properties of expansive soils.The properties of bagasse ash and cement treated expansive soils investigated include compaction characteristics,microstructure,splitting tensile strength,compressive strength,CBR value,shear wave velocity and small strain shear modulus.Soil specimens were prepared in different replacement proportions design.Standard compaction test,unconfined compressive strength test,CBR test,Brazilian split tensile test and bender element tests were conducted at different curing time of 7,14,and 28 days.XRD and SEM tests were also carried out.XRD revealed the major minerals are composed of quartz and crystobalite for bagasse ash.SEM indicates that there are different sized grains in bagasse ash,i.e.many fiber-shaped particles.The results obtained indicated that the substitution of OPC by bagasse ash would modify the compaction properties of treated soils,leading to less maximum dry density and higher optimum water content.The partial replacement of OPC by bagasse ash can also improve early strength of treated expansive soils.Result showed enhanced tensile strength with all the specimens with different proportion of replacement,which is possibly due to the long fiber structure of bagasse ash which is more resistant to tensile failure.The values of CBR of partial replaced specimens are even higher than the specimens treated with cement alone,when the replacement ratio is not greater than 20%.Bender element testing of the treated soils revealed that significant anisotropy in stiffness exists,but with the curing time and with replacement ratio,is gradually decreasing.From the test results,this research indicates that bagasse ash is an effective mineral admixture,CBA20(20%)as optimal replacement ratio of cement.The mechanisms of the stabilizing expansive soil by bagasse ash partial replacement of cement are discussed.