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Twenty-three different EFF mixtures were placed in trenches simulating utility cuts during March through May of 2001. All EFF mixtures were tested for flow, unit weight, gravimetric air content, suitability for load application, and compressive strength development over time. The trenches were excavated in March 2003. Excavation difficulty was correlated with laboratory compressive strength for non-air-entrained mixtures. Bearing capacity estimates with the dynamic cone penetration apparatus were determined for all trenches. Nine EFF mixtures were used to assess the impact of Portland cement content and ASTM C 618 Class F fly ash content. Portland cement contents of 17.8, 26.7, and 35.6 kg/m3 and ASTM C 618 Class F fly ash contents of 178, 219.5, and 261 kg/m3 were used to evaluate the impact of component proportions. Proportions for the EFF mixtures were chosen using Kentucky Transportation Cabinet and Tennessee Ready Mixed Concrete Association (TRMCA) recommendations as well as a previous Tennessee Technological University research mixture. Six EFF mixtures were used to assess the impact of Portland cement content and high-unburned carbon fly ash content Portland cement contents of 26.7 and 35.6 kg/m3 and high-unburned carbon fly ash contents of 219.5, 261, and 302.5 kg/m3 were used to evaluate the impact of component proportions. The influence of aggregate type on EFF mixtures was evaluated by using five different aggregate types in the EFF mixture recommended by TRMCA (26.7 kg/m3 Portland cement and 219.5 kg/m3 ASTM C 618 Class F fly ash). In addition, four comparison EFF mixtures were also used in the study (1 Tennessee Department of Transportation (TDOT) and 3 air-entrained EFF mixtures).

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