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The objective of the research was to determine if fly ash not meeting ASTM C618 can be used successfully in an aggregate-lime fly ash-stabilized base course (ALFASB). The Tennessee Dept. of Transportation (TDOT) Specification 312 for ALFASB includes hydrated lime, fly ash, and TDOT grading C limestone in percentages by dry weight of the total mix of 3.5, 11, and 85.5, respectively. The moisture content of the mix was determined by AASHTO T99. Hydrated lime is required to meet ASTM C977. Fly ash is required to meet ASTM C593 with several exceptions. TDOT grading C limestone was produced by blending No. 57 and limestone screenings. TDOT 312 requires an average compressive strength of 6.5-MPa (950-psi) for three specimens and no individual compressive strength less than 5.5-MPa (800-psi) after 28 days of curing at 37.8°C (100°F). Two different fly ashes were obtained: the control had a loss-on-ignition (LOI) of 1.6 %; the variable had an LOI of 8 %. Twenty-four (8 × 3) compressive strength specimens were fabricated for each set of materials. The only differences were fly ash and optimum moisture contents. The average compressive strength and coefficient of variation were 8.71-MPa (1263-psi) and 5.7 % for the control and 8.41-MPa (1219-psi) and 3.2 % for the variable, respectively. Each individual specimen met the compressive strength requirement for each fly ash. Sixteen (8 × 2) modulus of elasticity specimens were fabricated for each set of materials. The average static modulus of elasticity (estimated with ASTM C469) was 20.68-GPa (3000-ksi) and 15.81-GPa (2294-ksi) for the control and variable, respectively. These results indicate that a very high LOI fly ash can be useful as a stabilizing agent when used in combination with hydrated lime.
hydrated lime, fly ash, compression testing, soil stabilization
Crouch, L. K.
P.E. Professor, Dept. of Civil and Environmental Engineering, Tennessee Technological Univ., Cookeville, Tennessee
Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Tennessee Technological Univ., Cookeville, Tennessee
Knight, Marcus L.
Assistant Professor, Dept. of Concrete Industry Management, Middle Tennessee State Univ., Murfressboro, Tennesee