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APPENDIX B ASPHALT CONCRETE SPECIMEN PREPARATION B -1

OCR for page 315
APPENDIX B: ASPHALT CONCRETE SPECIMEN PREPARATION Watsonville granite aggregate and Valley AR-4000 grade asphalt were used for the asphalt concrete mix. Two different gradations, medium and coarse, were used during the course of this study and are descnbed in Table B.~. Table B. ~ . Medium and Coarse Gradations Percent Retained on Each Sieve by Weight Sieve Size Medium Gradation Coarse Gradation ~ in. 0 0 3/4 in. 5 10 I/2 in. 16 iS 3/S in. 12 12.5 No. 4 20 20 No. ~14 13 No. 16 I} 10 No. 30 ~9 , No. 50 5 2 No. 100 5 3 Pan (passing No. 100) 4 2.5 , . The aggregates were heated overnight at the mixing temperature of 284F. The asphalt was heated until the mixing temperature was achieved, the maximum allowable time of heating not exceeding 3.5 hours. Mixing time of 4 minutes was used. Optimum asphalt contents of 4.9 and 4.7 percent were used for mixing for medium and coarse gradation samples, respectively. After mixing the specimen was cured at 140F for 15 hours and then stored at room temperature. Before compaction the mix was placed at a temperature of 240F until it reached uniform temperature (normally within 1.5 hours). The mix was discarded if it was not used within 3 to 3.5 hours. Specimens were compacted by a Gyratory Testing Machine (GTM) to achieve 4 + 0.5 percent air voids. B-2