Asphalt overlays are one of the most common tools for rehabilitating existing asphalt and concrete pavements. However, the performance of new overlays is often jeopardized by the cracking distress in the existing pavement. This existing cracking propagates, or reflects, through the new overlay to the surface of the new overlay. The rate at which this reflection cracking propagates to the surface is a function of overlay thickness crack severity, traffic loading and subgrade or subbase support. Reducing the rate at which these reflection cracks propagate to the surface of the pavement is desirable in order to lengthen the time between rehabilitation projects or crack sealing operations.
Crack sealants are often utilized as a preservation tool in asphalt pavements. When a hot mix asphalt overlay is placed on top a pavement containing crack sealants, a bump and additional transverse cracks sometimes occur in the new asphalt overlay. These bumps and sometimes, transverse cracks are initiated during breakdown rolling and become progressively more severe upon further compaction. This paper presents results of a five-year study designed to identify factors that relate to the appearance of these bumps and consequent cracks.
In the past several decades, reinforced concrete structures have deteriorated similarly by chemical attack, especially chloride attack. For highway bridges, this phenomenon becomes more severe since bridges are exposed to extreme environmental conditions, such as snow and ice. In an effort to better protect the bridge decks and reduce maintenance costs. The use of WPMs was investigated by the Colorado Department of Transportation (CDOT) to analyze the performance of four products as an effective protection system.
Poor bonding between asphalt pavement overlays and the substrate pavement layer can greatly influence the long term performance of hot mix asphalt (HMA) in the form of premature cracking and fatigue. The primary method to achieve bonding between layers is by hot mix asphalt (HMA) in the form of premature cracking and fatigue. The primary method to achieve bonding between layers is by using an asphalt emulsion tack coat. Additionally, field staff is charged with determining whether an existing pavement, especially a milled surface, is clean enough prior to tack coat placement, to ensure an adequate bond.
The two objectives for this research were to review the 2016 asphalt mixture specifications to determine whether changes were warranted that could lead to more durable asphalt mixtures and, if so, adjust the specification accordingly and construct test sections to evaluate the revised specification.
