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cannot be easily estimated from the ï¬ller and binder properties. Mineral ï¬llers were found to signiï¬cantly affect mastic and mixture performance indicators and the ef- fects were, in most cases, highly speciï¬c to the ï¬ller- binder combination. Additionally, the ï¬ller volume concentration was found to have a signiï¬cant effect even when the mass ratio of ï¬ller to binder was kept constant at 1:1. These results suggest that the current practice of limiting dust (ï¬ller)-to-binder ratio by mass is insufficient as the practice cannot account for the effect of ï¬ller volume concentration on mixture or mastic performance. The experimental results clearly showed that fractional voids (packing) characteris- tics measured by RV vary signiï¬cantly among natural ï¬llers and have an important inï¬uence on mastic and mixture behavior. Varying mass ratio was not stud- ied; therefore, further study would be required to evaluate the role of the ï¬ller concentration on mastic performance. The effects of natural ï¬llers were found to be sig- niï¬cantly different from those of manufactured ï¬llers. Natural ï¬llers appear to inï¬uence mastic and mixture performance through a uniform physicochemical mechanism. Therefore, it was feasible to use regres- sion analysis to obtain a generalized prediction model for some properties of mastics containing natural ï¬llers. Manufactured ï¬llers, on the other hand, showed unique inï¬uences on the performance of mastic and mixtures studied in this project, and generalized trends could not be obtained; manufactured ï¬llers should be tested thoroughly after mixing with intended binders before they are introduced into the HMA mixture. CONCLUSIONS The following conclusions are based on the sta- tistical correlations and models developed for the ï¬ve speciï¬c HMA performance characteristics studied in the project. HMA Workability Mastic viscosity was successfully related to mix- ture workability, as measured by the number of gyra- tions to 92% Gmm (N92). Although N92 values were found to be highly dependent on aggregate gradation, the RV value was identified through multi-linear regression as the ï¬ller property that has an important inï¬uence on mastic viscosity and mixture workabil- ity. Tentative maximum limits for mastic relative viscosity were deï¬ned to ensure acceptable mixture compactability for coarse-graded mixtures. Speciï¬- cation limits for mixtures were estimated from the project data set since no speciï¬c guidance could be found in the literature. In cases where mastic testing is not possible, a statistical model to estimate mastic relative viscosity based on the RV value of the ï¬ller and the binder viscosity was proposed. The model can be used to check that the relative viscosity of mastic is below the maximum proposed limit. HMA Rutting Mastic rutting resistance was successfully related to mixture rutting resistance as measured by the ï¬ow number (FN) with AASHTO TP 79, Determining the Dynamic Modulus and Flow Number for Hot Mix As- 4 Filler Property Test Method Fractional Voids, reported as Rigden Voids (%) EN 1097-4, Tests for mechanical and physical properties of aggregates. Determination of the voids of dry compacted filler Size Distribution, reported as fineness modulus (FM) ASTM D4464, Particle Size Distribution of Catalytic Material by Laser Light Scattering Calcium Content, reported as % CaO X-ray Fluorescence, e.g., ASTM D5381, Standard Guide for X-ray Fluorescence (XRF) Spectroscopy of Pigments and Extenders Active Clay Content, reported as methylene blue value (MBV) AASHTO T 330, The Qualitative Detection of Harmful Clays of the Smectite Group in Aggregates Using Methylene Blue Specific Gravity, SG (required for determination of Rigden Voids ) Helium Pycnometer method, e.g., ASTM D5550, Specific Gravity of Soil Solids by Gas Pycnometer Table 4 Suggested test methods to measure performance-related ï¬ller properties.
