Free Swell Characteristics of PCC Bottom Ash-Bentonite Mixtures with Curing for Use as Fill or Liner Material

Bottom ash is a coal combustion product (CCP) obtained from burning of pulverized coal to produce electricity. Most of the bottom ash from pulverized coal combustion (PCC) plants is disposed of in landfills and/or ash ponds. Over the last decade, there has been increased attention aimed toward the use of PCC bottom ash in geotechnical applications. The particle size distribution of pulverized coal combustion (PCC) bottom ash is similar to that of natural sand. Natural sand is commonly used in the construction industry in place of cohesive soils by adding admixtures to amend its properties. Several studies have been completed to determine the properties of bottom ash amended with bentonite. However, due to significant volume change characteristics of bentonite, soils or similar granular materials amended with it need to be evaluated for their swelling behavior. In addition, studies on bottom ash-bentonite mixtures have shown that strength and stiffness characteristics of these mixtures change significantly with curing. Therefore, in order to evaluate the use of bottom ash as a fill or landfill liner material, this study was initiated to investigate the effect of curing and moisture content on the swelling characteristics of pulverized coal combustion bottom ash amended with bentonite. Bottom ash specimens containing 15 and 20 percent bentonite and prepared at 14, 16 and 18 percent initial moisture content were tested in this investigation. Results presented show the swelling characteristics of bottom ash-bentonite mixtures with curing age up to 60 days.