SOIL TREATMENT BY BENTONITE AND FLY ASH FOR LINERS OF WASTE LANDFILL: A CASE STUDY IN VIETNAM

Currently, a mixture of bentonite and soil is widely used for the bottom liner of landfill; however, the landfill using this mixture for the liner in Vietnam is limited. Therefore, this paper focuses mainly on investigating the physical and mechanical properties of soil samples from Hanoi, Vietnam; then compared their hydraulic conductivity before and after mixing with bentonite and fly ash in order to assess the efficiency of these mixtures for the landfill in Vietnam. From the hydraulic conductivity results, it was found that a mixture that has 15% or greater than15% of soil replaced by fly ash combined with bentonite (with the ratio between fly ash and bentonite is 4:1) can have the value of hydraulic conductivity (less than 1x10-9m/s) satisfies Vietnamese standard for bottom liner. Thus, this mixture can be used for landfill in Vietnam. In addition, several X-ray diffraction (XRD) tests along with Energy Dispersive X-ray Spectroscopy (EDX) on Scanning Electronic Microscopy (SEM) were also conducted for better understanding mechanism of reduction in hydraulic conductivity of mixed samples when bentonite combined fly ash added.