Click for next page ( 16


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 15
15 Table 9. Fine aggregate uncompacted voids content (Method A) and methylene blue values. Mixture ID FA-1 FA-2 FA-3 FA-4 FA-5b FA-6b Crushed Natural Natural Granite Dolomite Traprock Aggregate Type Gravel Sand A Sand B Sand Sand Sand Sand Uncompacted Voids Content, % Mixture Design 40.3 46.1 41.9 49.1 46.8 49.2 HMA Plant 39.2 47.6 42.0 48.9 46.2 49.3 Stockpile Sample Source HMA Plant 38.7 45.1 40.9 46.2 45.0 46.6 Mixture APT Cores 38.3 44.7 41.0 45.5 45.1 46.4 Methylene Blue Value Mixture Design 3.3 1.3 4.9 11.1 2.8 5.1 HMA Plant 7.8 1.3 5.5 5.8 2.8 6.9 Stockpile these three aggregates, the materials delivered to the hot-mix using specimens compacted to the Ndes value. Once the plant apparently had fines that were somewhat different from design binder content was selected, additional specimens the materials used in the mixture design. were compacted to Nmax to ensure that the mixture density at this point was less than 98 percent of the maximum theoret- ical density. Mixture Designs A 12.5-mm NMAS was used for all mixtures because of its wide use by highway agencies for HMA surface mix- All mixtures were designed using the Superpave volumet- tures. A single, unmodified asphalt binder, PG 64-22, was ric mixture design method outlined in the Asphalt Institute used in all mixtures, because it represents a typical neat Manual, SP-2, Superpave Level I Mix Design, and subsequent binder grade for much of the United States and is included addendum. The number of design gyrations, Ndes, and max- in most specifications. The experiments were designed to imum number of gyrations, Nmax, used for all designs were assess aggregate contribution to HMA mixture perform- 100 and 160, respectively. This compaction effort was ance. The complete binder and mixture design data are selected based on a design Equivalent Single Axle Load included in Appendix B, which is available in NCHRP Web- (ESAL) level of 3 to 30 million. Before compaction, all mix- Only Document 82. tures were aged for 2 hours at the compaction temperature. Design binder contents were selected at 4-percent air voids Coarse-Graded Mixtures 6 y = 0.42x - 15.16 A natural sand with a UVA of 40.3 percent was used as the R2 = 0.84 fine aggregate for all coarse HMA mixtures. The coarse- 5 graded mixture design data are given in Table 10. Traprock UVA Reduction #78 was initially used in the laboratory mixture design % Initial Value 4 process. However, because of the low design binder content 3 and VMA values, a different traprock stockpile (Traprock 2 #88) was evaluated and a second mixture design conducted with this aggregate. This second mixture was used in APT 1 testing. 0 35 40 45 50 55 Plant Stockpile UVA, % Fine-Graded Mixtures Figure 5. Fine aggregate A natural uncrushed gravel with a UVA of 42.2 percent was degradation. used as the coarse aggregate for all fine-graded HMA mixtures

OCR for page 15
16 Table 10. Mixture design data (at 4 percent air voids). Coarse-Graded Mixtures (Rutting and Fatigue) Mix No. VMA VFA %Gmm Pb (Pbe) Gmm DP Gse Gsb Ndes Nmax Ndes Nmax Nini Nmax CA-1 5.7 (4.7) 2.524 14.9 14.1 73.4 78.8 0.7 86.0 97.0 2.766 2.689 CA-2 6.1 (4.4) 2.447 14.0 13.2 71.5 76.7 0.9 85.4 96.9 2.688 2.566 CA-3 3.9 (2.9) 2.511 10.8 9.9 63.6 70.2 1.1 88.5 97.1 2.665 2.600 CA-4 5.8 (5.3) 2.461 16.0 15.1 75.1 80.8 0.7 87.0 97.1 2.691 2.652 CA-51 3.7 (3.1) 2.664 11.4 10.3 66.2 75.1 1.2 89.1 97.4 2.838 2.786 CA-5b2 4.8 (4.3) 2.630 14.3 13.6 72.0 77.5 0.6 88.2 97.0 2.853 2.808 1 Contained Traprock #78 and was not tested in the APT 2 Contained Traprock #88 and was tested in the APT Fine-Graded Mixtures (Rutting and Fatigue) Pb VMA VFA %Gmm Mix No. (Pbe) Gmm Ndes Req'd. Ndes Req'd. DP Nini Nmax Gse Gsb 6.0 FA-1 2.438 15.3 74.0 0.4 90.8 96.7 2.671 2.594 (4.9) 5.7 FA-2 2.447 16.2 75.2 0.7 88.3 96.9 2.669 2.638 (5.3) 5.8 FA-3 2.444 15.0 73.6 0.8 88.9 97.1 2.672 2.602 (4.8) 4.9 FA-4 2.460 14.3 73.0 1.9 88.1 97.3 2.651 2.625 (4.5) 14.0 65-75 7.4 FA-53 2.458 17.4 77.0 0.4 87.1 97.6 2.766 2.642 (5.7) 6.3 FA-63 2.565 18.0 77.9 0.6 87.2 97.4 2.851 2.811 (5.8) 6.3 FA-5b4 2.454 15.8 74.7 0.7 87.5 97.4 2.705 2.620 (5.1) 4.9 FA-6b4 2.619 14.4 72.2 1.6 87.7 97.2 2.845 2.797 (4.3) 3 Originally designed, but not tested in the APT 4 Prepared using fine aggregates from different source or gradation and tested in the APT Fine-Graded Mixtures (Moisture Susceptibility) VMA VFA %Gmm Mix No. Pb Gmm Ndes Req'd Ndes Req'd DP Nini Nmax Gse Gsb FAM-1 6.1 2.481 15.6 74.4 0.7 90.1 96.9 2.728 2.648 FAM-2 6.4 2.485 16.8 76.4 0.9 87.6 97.2 2.748 2.687 FAM-3 5.4 2.488 15.3 74.3 1.7 87.5 97.2 2.707 2.671 14.0 65-75 FAM-45 6.5 2.588 18.3 78.4 0.8 86.8 97.3 2.894 2.848 FAM-4b6 5.3 2.650 15.0 73.3 1.4 86.7 97.3 2.904 2.835 FAM-5 6.1 2.469 15.9 74.8 0.7 88.9 96.8 2.715 2.650 5 Originally designed, but not tested in the APT 6 Prepared using fine aggregates from the same source, but different gradation and tested in the APT in the rutting and fatigue studies. The mixture design data are Table 8). Mixture design results for these mixtures are shown shown in Table 10. in Table 10. Both have VFA values within the specification lim- Mixtures FA-5 and FA-6 are dolomite and traprock fine- its. Their dust proportions also increased considerably. graded aggregate mixtures, respectively. The compacted HMA mixtures using the original dolomite (Mixture FA-5) and Moisture Susceptibility Mixtures traprock (mixture FA-6) sands had high VMA values resulting in voids filled with asphalt (VFA) values above the maximum Five of the six fine aggregates used in the rutting study were allowed by specification. To remedy this problem, different selected for the moisture susceptibility experiment. Each fine dolomite and traprock fine aggregate stockpiles were identi- aggregate was combined with a common, crushed dolomite fied. These two new fine aggregates (FA-5b, FA-6b) had higher coarse aggregate and mixture designs were completed; mix- percentages of p0.075 material than the original materials (see ture design data are given in Table 10.