Abstract Chip seals have been the most frequently used preventive maintenance treatment on flexible pavements in the U.S. and overseas. Chip seals enhance transportation safety through 1) sealing small cracks, 2) reducing further oxidation of the pavement, 3) improving surface texture and skid resistance, 4) preserving and extending pavement life, and 5) providing color contrast and noise differences. Despite the growing number of chip seal projects in the U.S., many chip seal surface distresses such as aggregate loss, bleeding, and skid resistance still need to be solved, which are strongly related to aggregate embedment depth. Proper chip seal aggregate embedment should be evaluated as a critical factor when considering the design and construction of a chip seal project. In addition, road users are rapidly becoming less tolerant of travel delays caused by road works, so the research will benefit road users substantially by reducing the time involved in measuring the texture of existing surfaces. However, currently there is no reliable method to measure chip seal aggregate embedment quickly and accurately in the field. The objective of this study is to develop a photogrammetry-based method to rapidly determine the embedment depth of a uniformly placed chip seal of known aggregate gradation, easy to use, reasonably accurate, and inexpensive. The study will start with laboratory explorations with a photogrammetry-based method to measure the emulsion/binder application rate, final cover aggregate rate, and aggregate embedment. The effect of design factors (i.e., binder type, application rate, aggregate size, shape, and gradation) will be assessed as well.
Description Chip seals have been the most frequently used preventive maintenance treatment on flexible pavements in the U.S. and overseas. Chip seals enhance transportation safety through 1) sealing small cracks, 2) reducing further oxidation of the pavement, 3) improving surface texture and skid resistance, 4) preserving and extending pavement life, and 5) providing color contrast and noise differences. Despite the growing number of chip seal projects in the U.S., many chip seal surface distresses such as aggregate loss, bleeding, and skid resistance still need to be solved, which are strongly related to aggregate embedment depth. Proper chip seal aggregate embedment should be evaluated as a critical factor when considering the design and construction of a chip seal project. In addition, road users are rapidly becoming less tolerant of travel delays caused by road works, so the research will benefit road users substantially by reducing the time involved in measuring the texture of existing surfaces. However, currently there is no reliable method to measure chip seal aggregate embedment quickly and accurately in the field. The objective of this study is to develop a photogrammetry-based method to rapidly determine the embedment depth of a uniformly placed chip seal of known aggregate gradation, easy to use, reasonably accurate, and inexpensive. The study will start with laboratory explorations with a photogrammetry-based method to measure the emulsion/binder application rate, final cover aggregate rate, and aggregate embedment. The effect of design factors (i.e., binder type, application rate, aggregate size, shape, and gradation) will be assessed as well.
Objective The proposed research will address USDOT strategic goals such as a) Safety (primary strategic goal), b) Economic Strength and Global Competitiveness, c) Equity, and d) Climate and sustainability.
Impacts/Benefits The outcome of this project is a rapid, in situ method to determine the embedment depth of chip seal aggregate, which will greatly enhance the safety and efficiency during the construction. This information could then be used to address any contractor workmanship issues that may be occurring on the project in near real-time (vs. having to wait until after the project is entirely completed), as well as an indicator of performance relative to the initial chip seal design (i.e., target emulsion/asphalt and aggregate application rates, percent embedment range, etc.).