Use of Laser Texture Scanner to Control Quality of Chip Seal Construction

Chip seal is a pavement surface treatment, consisting of a combination of asphalt binder or emulsion and a layer of aggregate compacted on top of a pavement substrate. Raveling and bleeding are the two major distresses that affect the performance of chip seals. Studies have shown that these distresses can be related to the embedment depth, among a few factors. Embedment depth is the depth that rock is lodged into binder and is a key parameter that significantly affects the performance of chip seals. Currently, embedment depth is evaluated by pulling out the rock from the binder (often by a plier) and visually estimating the percentage of embedment. However, this method is subjective and does not provide accurate and reliable results. This study evaluated the use of laser texture scanner as quality control of chip seal construction. The mean profile depth (MPD), which is inversely related to percent embedment in the field, was measured and used to correlate with chip seal performance for raveling and bleeding. It was found that MPD is sensitive to compaction efforts of chip seals. The shoulder MPD value of chip seals after sweeping should be at a minimum of 0.150 in. to prevent bleeding from happening for the traffic volume experienced by the selected field project. When MPD in the wheelpath drops below 0.05 in., bleeding has occurred. More field experiments are needed to cover different construction practices and conditions to validate the findings from this study.