Development of Quality Assurance Procedures for Chip Seal Construction Using Macrotexture Metrics
Guangyuan Zhao, University of WaterlooShow Abstract
Shuo Li, Indiana Department of Transportation
Yi Jiang, Purdue University
Jusang Lee, Indiana Department of Transportation
Highway agencies typically use visual inspection as the performance measure for chip seal project. However, concerns have been raised regarding current quality assurance (QA) procedures, including the reliability and validity of visual inspections, time and labor, and operation safety. In response, this study aimed to develop novel concepts and provide cost-effective solutions to enhance current QA practices for chip seal construction. A macrotexture metric, mean profile depth (MPD), was selected to measure the quality of chip seals. Field visual inspection revealed that bleeding and excessive aggregate loss are the two primary distresses for new chip seals and are commonly found in the wheel paths. Thus, a field test protocol was developed, and extensive testing was conducted on the INDOT test track and chip-sealed pavements for validation. This study found that the use of at least two point-lasers, one for each wheel path, is needed to assess the characteristics and variation of macrotexture on chip-sealed surface. Macrotexture testing along one direction of traffic flow can provide sufficient information for QA and this testing should be performed early after the construction. In addition, the relationship between visual inspection rating and MPD was investigated by the developed regression models, which indicates that MPD measurements by the proposed test protocol, together with auxiliary visual inspection, can enhance the current chip seal QA procedures by accurately monitoring and predicting the performance of chip-sealed pavements.
Chip Seal Construction Variability and Its Impact on Performance
Jaehoon Jeong, North Carolina State UniversityShow Abstract
Javon Adams, North Carolina State University
Y. Richard Kim, North Carolina State University
This paper presents the findings obtained from field and laboratory experiments that were designed to assess the nature of chip seal construction variability in comparison to the targeted design and to investigate the impact of the variability on the performance of chip seal treatments. The research approach involved the construction of three double-seal test sections in Rowan, Moore, and Caswell Counties in North Carolina. Granite 78M and No. 14 aggregate and CRS-2L emulsion were used in the construction. Chip seal specimens were sampled from each of the three test sections. For these field samples, the aggregate application rate (AAR) and emulsion application rate (EAR) were determined using ignition oven tests. Chip seal performance was evaluated in terms of aggregate loss and bleeding using a third-scale model mobile load simulator (MMLS3). In addition, the fresh emulsions used in the test sections were tested using a rotational viscometer. The binder residue performance at high temperatures was assessed via multiple stress creep and recovery tests using a dynamic shear rheometer. The construction variability of the AARs and EARs and the emulsion residue properties were used to describe the aggregate loss and bleeding performance as determined by the MMLS3 and condition survey data that were obtained for the three chip seal projects one year after construction.
Performance-Based Percent Embedment Limits for Chip Seals
ilker Boz, Virginia Department of TransportationShow Abstract
Yogesh Kumbargeri, Michigan State University
Muhammed Kutay, Michigan State University
Chip seal treatments are used by many state Departments of Transportation and Counties to cover minor fatigue and low temperature cracks, retard raveling by reducing the moisture infiltration and improve friction. Long-term performance of a chip seal treatment is affected by several factors including the type and morphology of the aggregates, emulsion/binder type and most importantly, the microstructural characteristics such as the percent embedment of aggregates. This paper documents the efforts towards establishing performance-based threshold values of the percent embedment to minimize the common chip seal distresses (i.e., aggregate loss and bleeding). The laboratory performance tests were performed to evaluate aggregate loss and bleeding using a retrofitted Hamburg Wheel Tracking (HWT) device. Two emulsion types (CRS-2M and CSEA) and two aggregate sources (slag and natural aggregates) were included in the testing program. Digital image analysis techniques were utilized to quantify and analyze the laboratory test results with respect to the percent embedment as well as chip seal macrotexture. Based on the test results, the minimum and maximum percent embedment thresholds for chip seals are established as 58 and 70 percent, respectively.
Evaluation of the Effect of Percent Embedment and Aggregate Type on Chip Seal Performance Using Finite Element Analysis
Yogesh Kumbargeri, Michigan State UniversityShow Abstract
Anne Heidelberg, Michigan State University
Muhammed Kutay, Michigan State University
ilker Boz, Virginia Department of Transportation
Chip seal is one of the most popular pavement preservation strategies, however the design methods are mostly empirical in nature. Mechanistic analyses are needed to better understand microstructural factors (i.e. shape and percent embedment of aggregates) affecting the performance of chip seals. The objective of this study was to evaluate the effect of aggregate type and percent embedment of aggregates on chip seal behavior using laboratory tests as well as 2D Viscoelastic Finite Element (FE) analyses at multiple temperatures. Laboratory chip seal samples with cubical and flaky aggregates were prepared and subjected to sweep tests. 2D FE models were developed from actual images of chip seal specimens. The tensile strains at aggregate-binder interfaces were compared against the laboratory chip seal aggregate loss test results. Analyses revealed important inferences regarding aggregate loss susceptibility of chip seals made with different aggregate types. It was observed that the ranking of the performance of the flaky aggregates and cubical aggregates can be reversed, depending on the aggregate interlocking. In other words, the internal microstructure of the chip seal plays a crucial role on the performance of the chip seal. In addition to the type of emulsion, type of aggregate and the percent embedment, the internal structure of the chip seal, especially the aggregate interlocking should be considered in chip seal design.