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A project to develop a new method or adapt a current method with wide applicability for determining bulk specific gravity of compacted hot-mix asphalt (HMA) mixtures ( Gmb) is described. A more reliable Gmb would result in more reliable HMA volumetric properties, specifically, percent air voids. Consequently, pavement distress types such as rutting, bleeding, stripping, and age hardening (whose occurrence is related to percent air voids, among other factors) could be avoided more often. The project goal was accomplished in three steps. In Step 1, a literature review and survey of state departments of transportation revealed 13 existing Gmb determination techniques. In Step 2, a feasibility study of the seven methods selected was conducted to evaluate cost, logistical factors, and preliminary repeatability. In the final step, 50 compacted HMA samples and four aluminum cylinders were used to evaluate the precision and accuracy of the four methods selected. The dimensional analysis (AASHTO T269) and the parafilm (ASTM D1188) methods were found to form upper bounds for true sample air voids, whereas the saturated surface-dry method (AASHTO T166) was found to form a lower bound for true air voids. Although the true air voids can never be determined, for 90% of Tennessee Department of Transportation sample groups tested, the InstroTek Corelok method yielded results in this range between the upper and lower bounds for accurate air void results. In the precision and accuracy evaluation, all four methods were found to be capable of producing high-precision results.

Before the development of performance-enhancing admixtures, flowable fill mixes bled off excess mix water to consolidate after placement. The presence of significant amounts of material finer than 0.075 mm in the aggregate impeded bleeding, and therefore, most specifying agencies limited the percentage allowed to less than ten. New performance-enhancing admixtures limit strength, prevent segregation, and enhance workability by entraining large percentages of stable air bubbles in flowable fill mixtures. Flowable fill mixtures containing these admixtures do not bleed and, therefore, could possibly use aggregates containing greater than 10% finer than 0.075 mm. It was determined that aggregate containing up to 21% finer than 0.075 mm could be used to produce a flowable fill mix meeting National Ready Mixed Concrete Association performance recommendations.

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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