Road base mixed with cement8/10/2023 ![]() ![]() The five combinations should span the recommended range of ratios for each activator. Use five different activator-to-fly ash combinations at the optimum matrix content. Then determine the optimum moisture content and maximum dry density for that blend.ĭetermine the most suitable proportions of activator to fly ash. Select an optimum matrix content at least two percent above the matrix content found at the maximum dry density. ![]() Plot the test results to identify a peak value or maximum dry density. Mold one test specimen at each fly ash content in accordance with ASTM C 593 compaction procedures at an estimated optimum moisture content.ĭetermine the molded dry density of each aggregate-fly ash blend. Add fly ash to the aggregate in five different proportions, starting at the lower limit (10 percent for coarse aggregate) and proceed in convenient increments to the upper limit (20 percent for coarse aggregate). Use proctor-size molds for all test samples. Screen the aggregate through a three-quarter-inch sieve, and use the portion passing the three-quarter-inch sieve for testing. Determine the particle size distribution of the aggregate. Obtain a representative sample of aggregate. The following steps summarize the procedures for a laboratory determination of mix proportions: The vacuum saturation test is normally used per ASTM C 593. It is important to ensure that adequate resistance to freeze-thaw cycling is achieved before the onset of colder months. Some states use different curing times and temperatures.ĭurability. Use standard proctor-sized specimens normal curing for lime/fly ash/aggregate mixtures is at plus 38 degrees C (100 degrees F) for 7 days. Closely controlled curing conditions are important as both time and temperature significantly affect strength. Permits better use of open graded base courses.Allows the use of marginal or low quality aggregates.Adds significant strength and durability.The stabilization of aggregate bases provides several advantages: Also, 0.5 to 1.5 percent Type I portland cement can be blended with Class F fly ash to produce the stabilizing agent. Typical proportions for the Class F fly ash lime blends are two to eight percent lime blended with 10 to 15 percent Class F fly ash. Class F fly ash can be used when blended with lime, portland cement or cement kiln dust (CKD). Class C fly ash can be used as a stand-alone material. This application, termed pozzolanic-stabilized mixture (PSM) uses several materials and material combinations to construct stabilized aggregate bases. The stabilization of aggregate road bases with fly ash has a long and successful history. Mix Design and Specification Requirements Fly ash stabilized base course is suitable for both flexible and rigid pavements. Fly ash stabilized base courses are cost-effective substitutes for properly engineered full-depth asphalt, cement-treated, and crushed stone base courses. Mix Design and Specification Requirementsįly ash stabilized base courses are proportioned mixtures of fly ash, aggregate, and an activator (cement or lime) that, when properly placed and compacted, produce a strong and durable pavement base course. ![]()
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