Density Evaluation of the Longitudinal Construction Joint of Hot-Mix Asphalt Pavements

When placing hot-mix asphalt concrete (HMAC), paving the full width of the pavement in a single pass is usually impossible; therefore, most bituminous pavements contain longitudinal construction joints. These construction joints can often be inferior to the rest of the pavement and can eventually cause an otherwise sound pavement to deteriorate more quickly. The objectives of this project were to (1) assess the density along the longitudinal construction joint of several Texas pavements to determine if a problem exists; (2)document information from the literature; (3) synthesize aviation construction data where a history of a jointdensity specification exists to determine if such a requirement can be met by paving contractors; and (4)modify current HMAC specifications to require joint density measurements if justification is verified. Results of this project confirmed what was found in the literature: there is an area of low density in the edge of the lane paved first. Field evaluations conducted on 35 Texas pavements in this project found that the density was always lower at the unconfined edge than in the middle of the lane and this was almost always statistically significant. This difference in density could range from 2 to 12 lbs per cubic ft but the average was about 6 to 7 lbs per cubic ft (or 4 to 5 percentage points). Aviation data analyzed in this project indicate that contractors are routinely able to meet the joint density requirements as specified in the Federal Aviation Administration (FAA) P-401 specification. The data in this project provide for a very strong indication that a joint density specification is justified.