Affiliations: Dept. of Civil Engineering, Amrita School of
Engineering, Bangalore – 560035, India | Dept. of Civil Engineering, BMS College of
Engineering, Bangalore – 560019, India | Dept. of Civil Engineering, Indian Institute of
Science, Bangalore – 560012, India
Abstract: Laboratory hydraulic conductivity (HC) tests have been conducted on
mixtures of fine sand with bentonite and fly ash with four fluids with
different pH and metal concentrations with a view to assess their suitability
for liner constructions for waste containment facilities. HC of sand-bentonite
mixtures which was low, due to effective reduction void ratio because of
swelling of negatively charged bentonite particles, further reduces with
increase in the density and with increase in the pH of the fluid by increase in
the cation exchange capacity and fabric of the clay assuming relatively more
dispersed structure. The hydraulic conductivity of mixtures of fly ash sand
were higher and were in the range of 1 × 10^{-5} cm/s
which however decreases slightly with increase in the density. HC of sand fly
ash mixtures with increase in pH of the solution due to increase in the reactivity
of fly ash in alkaline medium produces more pozzolanic compounds leading to reduction
in the void ratio. It is also found, however, that hydraulic conductivity of
fly ash mixtures is not suitable for liner application. The precipitation of
metal ions at higher pH in sand fly ash mixtures may reduce the HC depending on
the concentration of metal ions. However, bentonite needs to be incorporated to
lower the HC range required for liner application. Thus both sand bentonite and
sand fly ash-bentonite mixtures can be used for liner application for waste
containment facilities.
