EVALUATION OF STRUCTURAL LAYER COEFFICIENTS FOR ASPHALT EMULSION-AGGREGATE MIXTURES.
AuthorMEIER, WELLINGTON R., JR.
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe extensively used AASHTO structural design procedures for flexible pavement indicate the required pavement design in terms of a structural number. For a particular pavement thickness design, this structural number can be computed from the sum of each pavement layer's thickness multiplied by its strength parameter, called the structural layer coefficient. The research work reported herein presents methods for determining the structural layer coefficients for asphalt emulsion-aggregate mixtures. A hot plant-mixed asphaltic concrete was evaluated for structural layer coefficient, and the radial stress vs. fatigue failure relationship was developed using circular specimens and the Jimenez deflectometer. Relationships between structural number and load repetitions to failure for different loading conditions were developed. These relationships were used to evaluate the structural numbers of other specimens when tested to failure in flexural fatigue. Three asphalt emulsion-aggregate mixtures were designed using CSS-lh asphalt emulsion. The aggregates used for the three mixtures were: (1) Type I aggregate using dense-graded, crushed, river gravel; (2) Type II aggregate using pit-run, coarse sand; and (3) Type III aggregate using a silty sand. These mixtures were evaluated for Marshall stability, Hveem stability and cohesiometer value, unconfined compressive strength, double punch tensile strength and dynamic modulus of elasticity at various ages from 3 to 28 days. Flexural fatigue life, when tested in the deflectometer, was determined for all mixtures at 7 and 28 days. Structural numbers for the specimens and structural layer coefficients for the mixtures were determined. Relationships were developed between the evaluation tests performed and the structural layer coefficients at various mixture ages by using test results from the three mixtures and a regression analysis procedure. A fourth asphalt emulsion-aggregate mixture using CSS-lh asphalt emulsion and a Type II crusher-run aggregate was designed. Evaluation tests were performed at 3 and 7 days and layer coefficients for the mixture were predicted for 7 and 28 days using the regression equations developed. Layer coefficients at 7 and 28 days were also determined by testing specimens in fatigue in the deflectometer and computing their structural numbers and layer coefficients. Layer coefficients determined in these two manners indicated favorable comparisons. The results of this research provides information about the structural layer coefficients for asphalt emulsion-aggregate mixtures. The relationships between the evaluation tests and structural layer coefficient can be used for determining layer coefficients for other asphalt emulsion-aggregate mixtures. Because the evaluation tests used were tests commonly performed in most asphalt laboratories, these determinations can be made without the necessity of additional equipment or procedures in most cases.
Degree ProgramCivil Engineering