道路工程施工概况(英文).docVIP

Overview Construction quality is crucial to the long-term pavement performance. Construction factors such as surface preparation, placement, joint construction and compaction/consolidation have an overwhelming effect on pavement performance, which cannot be ignored or compensated for in mix or structural design. Compaction Compaction is the process by which the volume of air in an HMA mixture is reduced by using external forces to reorient the constituent aggregate particles into a more closely spaced arrangement. This reduction of air volume produces a corresponding increase in HMA density (Roberts et al., 1996[1]). Figure 1: A Steel Wheel and a Pneumatic Tire Roller Working Side-by-Side. Compaction is the greatest determining factor in dense graded pavement performance (Scherocman and Martenson, 1984[2]; Scherocman, 1984[3]; Geller, 1984[4]; Brown, 1984[5]; Bell et. al., 1984[6]; Hughes, 1984[7]; Hughes, 1989[8]). Inadequate compaction results in a pavement with decreased stiffness, reduced fatigue life, accelerated aging/decreased durability, rutting, raveling, and moisture susceptibility (Hughes, 1984[7]; Hughes, 1989[8]). Compaction Measurement and Reporting Compaction reduces the volume of air in HMA. Therefore, the characteristic of concern is the volume of air within the compacted pavement, which is typically quantified as a percentage of air voids in relation to total volume and expressed as “percent air voids”. Percent air voids is calculated by comparing a test specimen’s density with the density it would theoretically have if all the air voids were removed, known as “theoretical maximum density” (TMD) or “Rice density” after the test procedure inventor. Although percent air voids is the HMA characteristic of interest, measurements are usually reported as a measured density in relation to a reference density. This is done by reporting density as: Percentage of TMD (or “percent Rice”). This expression of density is easy to convert to air voids because any