Test Methods and Specification Criteria for Mineral Filler Used in Hot-Mix Asphalt (2011)

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Research Results Digest 357 June 2011 INTRODUCTION While there is no lack of evidence that mineral fillers can have important effects on the performance of hot mix asphalt (HMA) (and, by extension, that of warm mix asphalt, WMA), current HMA mixture design procedures and materials specifica- tions include only general limits on filler- to-binder mass ratio. Thus, these procedures and specifications, notably AASHTO R 35, Superpave Volumetric Design for Hot Mix Asphalt (HMA), are silent on the possible influence of fillers on key indicators of HMA performance. The objectives of NCHRP Project 9-45, “Test Methods and Specification Criteria for Mineral Filler Used in Hot Mix Asphalt,” were to (1) identify (or develop, as neces- sary) test methods for mineral filler that characterize its physical and chemical ef- fects on the performance of mastics (blends of asphalt binder and mineral filler) and HMA and (2) propose specification criteria for mineral filler that help optimize HMA performance. RESEARCH PLAN A comprehensive literature review was conducted to evaluate current knowledge of the characterization of mineral fillers and the measurement of filler effects on mastics and HMA. The state departments of transportation were also surveyed for their views on the most critical aspects of the use and specification of mineral filler. Based on the findings of the literature re- view and survey, an experimental plan was developed to evaluate a select set of filler properties and associated test methods that were identified as having the potential to critically influence mastic performance, HMA mixture performance, or both. The tests included physical tests to characterize filler geometry and chemical tests to char- acterize filler composition. The 32 fillers shown in Table 1 were selected for testing in the experimental phase of the project. These fillers repre- sent the wide ranges commonly found in the United States of (1) mineralogy of natural fillers (those produced in quarries TEST METHODS AND SPECIFICATION CRITERIA FOR MINERAL FILLER USED IN HOT MIX ASPHALT This digest summarizes key findings of NCHRP Project 9-45, “Test Methods and Specification Criteria for Mineral Filler Used in HMA,” conducted by the University of Wisconsin–Madison under the direction of the principal investigator, Hussain U. Bahia. The digest is based on the project final report authored by Hussain U. Bahia, Ahmed Faheem, and Cassie Hintz of the University of Wisconsin–Madison; Imad Al-Qadi of the University of Illinois at Urbana–Champaign; and Gerald Reinke and Erv Dukatz of Mathy Technical Engineering Services. The full text of the project final report is available for download at http://apps.trb.org/cmsfeed/ TRBNetProjectDisplay.asp?ProjectID=979. Responsible Senior Program Officer: E.T. Harrigan NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

during rock processing or collected in baghouse collectors during HMA production) and (2) com- position of manufactured fillers (those such as fly ash and slag dust that are byproducts of industrial processes). The project team later dropped the two carbon black fillers (CBC1 and CBF1) from the experiment because they are extremely fine with low density, which made them easily airborne and difficult to handle. Also, the Portland cement (CM1) was not tested with the methylene blue (MB) method for active clay content because of this filler’s reac- tivity with water. Based on the initial testing of these 32 fillers, a subset of 17 fillers was selected for blending with four asphalt binders to create a total of 68 mastics for testing using the methods in Table 2. The four binders were (1) a PG 64-22 with low asphaltenes content from a light crude source, (2) a PG 64-22 with high asphaltenes content from a heavy crude source, (3) the light crude PG 64-22 modified with PPA to a PG 70-22, and (4) the light crude PG 64-22 modified with SBS to a PG 70-22. Upon completion of mastic performance test- ing, 16 mastics were selected for blending to pre- 2 No. Code Type Rigden Voids (%) FM1 CaO 2 (%) MBV 3 SG4 PI5 1 AN1 Andesite 41.9 5.18 6.80 24.56 2.60 Non-Plastic 2 BH1 Hard Basalt 33.2 5.31 8.20 5.92 2.72 Non-Plastic 3 BH2 Hard Basalt 33.8 4.65 7.00 11.19 2.77 Non-Plastic 4 BV1 Vesicular Basalt 37.8 4.59 9.10 11.65 2.79 3.00 5 CA1 Caliches 40.3 4.91 44.00 8.96 2.59 Non-Plastic 6 CA2 Caliches 45.0 5.13 40.00 10.25 2.49 Non-Plastic 7 CBC1 Carbon Black NA NA NA NA NA NA 8 CBF1 Carbon Black NA NA NA NA NA NA 9 CM1 PortlandCement 30.0 4.27 14.30 NA 2.87 Non-Plastic 10 DH1 Hard Dolomite 42.8 5.07 26.00 2.79 2.59 Non-Plastic 11 DH2 Hard Dolomite 27.0 4.54 32.01 0.99 2.61 Non-Plastic 12 DS1 Soft Dolomite 34.7 6.02 26.00 1.17 2.71 10.00 13 DS2 Soft Dolomite 29.4 4.73 27.00 1.82 2.70 Non-Plastic 14 FAC1 Fly Ash Type ‘C’ 26.2 3.30 25.03 0.00 2.47 Non-Plastic 15 FAC2 Fly Ash Type ‘C’ 26.2 3.88 23.13 0.00 2.37 Non-Plastic 16 FAF1 Fly Ash Type ‘F’ 30.1 4.29 5.10 0.39 2.14 Non-Plastic 17 FAN1 Fly Ash Non Spec 40.5 3.22 21.80 0.01 2.38 Non-Plastic 18 FAN2 Fly Ash Non Spec 28.9 2.98 24.45 0.02 2.54 Non-Plastic 19 FS1 Furnace Slag 40.0 4.87 50.30 0.00 2.80 Non-Plastic 20 FS2 Furnace Slag 49.1 4.32 45.07 0.02 2.89 Non-Plastic 21 GH1 Hard Granite 42.6 4.06 3.50 2.35 2.66 Non-Plastic 22 GH2 Hard Granite 38.8 3.76 2.80 31.56 2.53 8.00 23 GHB1 Hard Granite Baghouse 38.3 4.26 4.70 2.81 2.62 6.00 24 GRQ1 Gravel Quartzite 29.5 4.39 32.70 2.06 2.66 Non-Plastic 25 GRQ2 Gravel Quartzite 36.5 6.32 0.95 0.66 2.55 Non-Plastic 26 GS1 Soft Granite 40.2 3.85 4.60 14.47 2.58 Non-Plastic 27 GS2 Soft Granite 47.0 3.13 7.80 0.88 2.40 Non-Plastic 28 HL1 Hydrated Lime 38.8 4.74 27.60 0.80 2.70 Non-Plastic 29 HL2 Hydrated Lime 38.1 4.15 32.20 1.05 2.79 Non-Plastic 30 LH1 Hard Limestone 32.2 5.63 43.14 0.62 2.65 Non-Plastic 31 LS1 Soft Limestone 26.2 4.30 49.20 0.00 2.64 Non-Plastic 32 LS2 Soft Limestone 35.4 3.68 46.30 3.87 2.62 Non-Plastic Notes: 1. Size distribution reported as fineness modulus (FM). 2. Total calcium content reported as percent calcium oxide (CaO). 3. Active clay content reported as the methylene blue value (MBV). 4. SG = specific gravity. 5. PI = plasticity index per AASHTO T 90, Determining the Plastic Limit and Plasticity Index of Soils. Table 1 Summary of filler testing results.