Geotechnical Properties of Fly Ash and Lime - Fly Ash Stabilized Coal Mine Refuse Sanjeev Kumar Assistant Professor, Department of Civil Engineering, Southern Illinois University - Carbondale, Carbondale, Illinois, USA Vijay K. Puri Professor, Department of Civil Engineering, Southern Illinois University - Carbondale, Carbondale, Illinois, USA Braja M. Das Professor and Dean, College of Engineering & Computer Science, California State University, Sacramento, Sacramento, CA, USA Bimal C. Devkota Former Graduate Student, Department of Civil Engineering, Southern Illinois University - Carbondale, Carbondale, Illinois, USA
				ABSTRACT

This paper describes the results of a study which was primarily directed to the determination of geotechnical properties of stabilized fine coal refuse obtained from one of the mines in southern Illinois to assess its suitability for highway construction work. Coal refuse samples used were stabilized by treating with flyash, and lime-flyash mixtures in various proportions. The geotechnical properties investigated were: (a) compaction characteristics, (b) triaxial shear strength, (c) CBR, and (d) hydraulic conductivity. It was observed that addition of about 10-15% flyash to coal refuse, increased the shearing strength by more than 35%. Addition of small amounts of lime caused a significant increase in shear strength of coal refuse. CBR tests showed a trend similar to that observed for shear strength. The hydraulic conductivity of lime-flyash treated samples was in the range of 4 x 10^-8 cm/sec to 1.4 x 10^-7 cm/sec, and showed a decreasing trend with increase in curing time. The fine coal refuse, alone or with flyash or lime-flyash admixtures, possesses acceptable compaction characteristics. It appears from the test results that the fine coal refuse used in this study can be properly stabilized for use in construction of highway subgrades and embankments, thus eliminating the need for additional land for stockpiling.

KEYWORDS: Coal refuse, flyash, lime

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