Sealing, patching, and thin surfacing activities are among the most common pavement maintenance actions used by transportation agencies. This session explores different topics associated with these activities, including both experimental applications and proven technologies. This session will be of interest to practitioners and researchers alike.
The Effect of the Interaction between Bituminous Seals and their Substrates on the Performance of Road Pavements in Tropical Environments
ANDREW OTTO, TRL LIMITEDShow Abstract
Jasper Cook, Independent Consultant
The performance of pavements is governed by the characteristics of the materials of the individual pavement layers, the support provided by underlying layers, and the overall pavement strength to withstand the traffic stresses. These factors vary seasonally and in the long-term as the materials age. Bituminous seals are an expensive layer of the pavement system and thus their failure should be minimised by proper selection of the appropriate technology combination. An understanding of the mechanism by which failure is induced through the use of inappropriate combinations of seal and substrate is important to ensure longevity of the pavement. This paper examines 6 case studies to demonstrate cases where substrate failure was initiated by failure of the seal and where seal failure is initiated by changes in the substrate conditions. The effect of climatic factors such as rainfall and poor drainage, and bitumen ageing are considered. Bitumen ageing is severe under tropical conditions. Failure mechanisms are postulated for each of the case studies examined. As a result of the examination of these case studies, it was apparent that the choice of seal and substrate combinations play an important role in pavement performance. Historically weak seals such as sand seal performed better when laid on strong substrates/bases. WPavements comprising moisture susceptible substrates induced defects on thin seals, although seals with thicker bitumen films, such as Otta seal performed comparatively better when used on those substrates.
A review of flexible pavement pothole patching methods and guidelines in the United States
Yujia Lu (email@example.com), University of Illinois, Urbana-ChampaignShow Abstract
Ramez Hajj, University of Illinois, Urbana-Champaign
Potholes are a common and persistent surface distress experienced by asphalt pavements, which result in premature pavement failure and damage to vehicles. The formation of potholes is the result of many complex interactions, including freeze/thaw cycles, traffic loading, aging of the asphalt concrete layer, and other potential causes. Within the United States and even within single agencies, there are a wide variety of methods for repairing potholes. This creates difficulty in understanding the effectiveness of pothole repair procedures and developing strong patching strategies. Therefore, the objectives of this paper are twofold: (i) to summarize the most common patching methods based on a literature review and (ii) to investigate the methods used to patch potholes within each state in the United States and other countries around the world from the perspectives of techniques, materials, equipment. Based on the findings of this study, it is evident that in general, many states do not have guidelines, and those that do are often general. It is highly recommended to develop centralized patching guidelines and implement acceptance tests to be used for patching materials.
Quantitative Measurement of Crack Sealing Benefit using 3D Laser Technology and 3-Year Crack Growth Measurement in the Field
Zhongyu Yang, Georgia Institute of Technology (Georgia Tech)Show Abstract
Xinyi Zhang, Georgia Institute of Technology (Georgia Tech)
Yichang Tsai, Georgia Institute of Technology (Georgia Tech)
Crack sealing is one of the most used asphalt pavement preservation methods. However, quantitative measurement of the long-term crack sealing benefit based on the crack length growth retardation is still limited due to the lack of an accurate and effective crack length measurement method in the field. This is the first study that proposes using a 3D laser technology that measures crack length growth to quantitatively measure the crack sealing benefit by comparing the crack length growth between crack sealed and non-sealed sections of pavement. Also, this study analyzes the long-term field actual crack sealing benefit in different pretreatment pavement conditions and under the different roadway environmental factors to study adequate treatment timing. The field study included nine test sites located in Georgia (six in Hawkinsville, southern GA; three in Covington, central GA) with different pretreatment pavement conditions (pavement rating 66-98 ) and different roadway environmental factors (pavement thickness 2.5-10 inches; traffic volume 1,030-12,900; truck 3%-26%) was conducted over 3 years (Dec. 2017-Sep. 2020). The experimental results show crack sealing can effectively retard crack growth by 40-128%. Results show crack sealing benefit is higher when applying crack sealing at a higher pavement condition rating. This finding suggests that transportation agencies can apply crack sealing to prolong the life of healthier conditioned pavement rather than prolong the life of the poor conditioned pavement. These results are very valuable for transportation agencies to determine the right crack sealing timing and treatment criteria.
Short-term Field Performance and Cost-effectiveness of Crumb-Rubber Modified Asphalt Emulsion in Chip Seal Applications
Md Nafiur Rahman, Louisiana State UniversityShow Abstract
Md Tanvir Ahmed Sarkar, Auburn University
Mostafa Elseifi (firstname.lastname@example.org), Louisiana State University
Corey Mayeux, Louisiana Department of Transportation and Development
Samuel Cooper, Louisiana Department of Transportation and Development
Ken Free, Louisiana Department of Transportation and Development
Chip sealing is a commonly used pavement maintenance technique that aims to delay pavement deterioration by reducing water infiltration and restoring skid resistance. The objective of this study was to evaluate the short-term field performance and cost-effectiveness of chip seals prepared with different types of asphalt emulsions and their application rates. A newly introduced crumb-rubber modified asphalt emulsion was evaluated that allows chip seal installation at the same temperature of a standard emulsion. Types of emulsion included a crumb-rubber modified asphalt emulsion (CRS-2TR), a polymer-modified emulsion (CRS-2P), and a conventional unmodified emulsion (CRS-2). Application rates were obtained from the Louisiana Department of Transportation and Development (LaDOTD), the Texas Department of Transportation (TxDOT) specifications, as well as, from the chip seal design method recommended in NCHRP Report 680. Seven chip seal sections were constructed and were regularly monitored over a 12-month period. In the northbound lane, the chip seal section constructed with CRS-2TR (0.37 gsy) was the best performer statistically. In the southbound lane, the chip seal sections constructed with CRS-2TR and CRS-2P (0.31 gsy) performed similarly. Furthermore, the maximum Service Life Extension (SLE) was observed for the CRS-2TR (0.31 gsy) chip seal sections, whereas the chip seal sections constructed with CRS-2 were observed with the minimum SLE. In addition, the most cost-effective chip seal section was achieved by the application of CRS-2TR emulsion at the LaDOTD recommended emulsion application rate.
Experimental Evaluation of Chip Seal Interlayer Over Soil-cement Bases as Reflective Crack Mitigation Technique
Mohammad Khattak (email@example.com), University of Louisiana, LafayetteShow Abstract
Mohammad Bhuyan, University of Louisiana, Lafayette
Soil-cement stabilized base naturally develops shrinkage cracks that reflect up to the surface layer of flexible pavements. As these reflective cracks deteriorate pavements, highway agencies are struggling to mitigate those cracks. In an effort to mitigate such cracks, Louisiana Department of Transportation and Development has been installing Chip Seal as an interlayer between the base and surface layer. Chip Seal is a type of asphalt surface treatment and the idea of installing it as an interlayer over soil-cement bases is nascent. This research aims to evaluate the effectiveness of Chip Seal as an interlayer by laboratory experiments. In this study, the Chip Seal interlayer was constructed and beam specimen with and without interlayer over soil-cement were prepared for laboratory fatigue testing. Repeated haversine loading using Material Testing Systems was applied and the fatigue lives were determined. Simultaneously using Digital Image Correlation (DIC) technique, images at regular intervals were captured during the testing. The DIC images were analyzed to understand the distribution of horizontal plastic strain map in asphalt layer and interlayer around the vicinity of loading. From the comparison of fatigue lives of specimens, it was ascertained that Chip Seal interlayer had increased the lives up to 60%. The DIC image analysis clearly showed initiation and propagation of reflective cracks and the effect of the interlayer on reflective cracking. The gradual deterioration and change in strain distribution map in Chip Seal was also illustrated with the help of DIC imaging technique.
An Experimental Study on the Design and Behavior of Concrete Pavement Joint Sealants
Jinho Kim, Texas A&M University, College StationShow Abstract
Dan Zollinger, Texas A&M University, College Station
Seunghyun Lee, Texas A&M University, College Station
Joints in concrete pavement are intended to provide freedom of movement to a concrete slab relative to the volumetric effects. Changes such as this can occur due to drying shrinkage, temperature changes, and moisture differences that develop within the slab. A key reason to seal rigid pavement joints is to prevent or at least reduce the amount of water infiltrating the pavement structure, which can result in subbase erosion, loss of support, and the build-up of incompressible material on the face of the joint. The strength of the joint sealant bond and stress of the interface between the sealant and face of the joint reservoir play important roles in joint sealant failure. Thus, in this research, experimental coupling tests were conducted to investigate the geometric characteristics of sealant/joint reservoir design. The stress distribution on the interface was investigated according to its geometry, both in terms of the shape factor (SF) and degree of curvature (DoC). The SF and DoC were evaluated through a tensile test of the joint sealant based on these geometric characteristics. Also discussed are the SF of the joint sealant currently being recommended, SF most appropriate for a narrow-width joint, and surface finish of joint sealant. Based on this study, the effects of sealant geometries (i.e., SF and DoC) should be considered during design and installation. Also, further research on more realistic SFs for narrow-width joints and self-leveling sealants is needed.
Pothole Repair in Asphalt Pavement: Current Practice and New Materials and Techniques
Xiao Chen, Rutgers UniversityShow Abstract
Hao Wang (firstname.lastname@example.org), Rutgers University
Giri Venkiteela, New Jersey Department of Transportation
Pothole repair in asphalt concrete pavements is one of the most commonly performed highway maintenance treatments. The cost-effective pothole repair could increase driving comfort, improve road safety and decrease agency and use costs. This study summarized the current practice of pothole repair and identified new patch material and pothole repair method with heating through extensive literature review. The feasibility of using heating methods in pothole repair was further studied using life cycle cost analysis (LCCA). The best practice shows that in normal construction seasons, throw and roll method with qualified materials is recommended for repairing potholes less than 2 inches. When the depth of pothole is over 2 inches, semi-permanent is recommended to ensure a good bonding condition at the interface. The LCCA results show that microwave heating method is feasible to be used in pothole repair in winter and achieve better cost effectiveness. Cold mix asphalt modified polymer, resin, fiber, or cementitious material showed potential of better performance for pothole repair. However, field tests need be conducted to validate laboratory testing results. Finally, a decision tree was developed to help state agencies select cost-effective pothole repair method.
Water Film Depth Prediction Model for Chip Seal Surface Drainage
Alireza Pourhassan, Missouri University of Science and TechnologyShow Abstract
Ahmed Gheni, Missouri University of Science and Technology
Mohamed ElGawady, Missouri University of Science and Technology
Water film depth (WFD) is an essential factor regarding road traffic safety on the roads due to its direct connection with skid resistance, hydroplaning speed, and the tendency of splash and spray. Increasing the pavement macrotexture is one of the solutions to reduce the WFD. Therefore, chip seal can be a viable option for reducing the WFD. However, the existing models of WFD prediction are not developed based on highly textured surfaces like chip seal. Besides, the rainfall intensity ranges used for developing most of these models do not raise safety issues on chip seal surfaces. To propose a new WFD prediction model, an experimental study was conducted on 154 different combinations of texture depth, surface material type, surface slope, drainage length, and rainfall intensity using a full-scale rainfall simulator. To study the effects of surface material type and also evaluate the newly proposed eco-friendly rubberized chip seal, mineral aggregate and crumb rubber were used as aggregate. Test results through 1,784 WFD readings indicated that the well-known Gallaway and PAVDRN models are not accurate for chip seal surfaces. Hence, two new analytical models were proposed to predict the WFD, which showed a significantly higher correlation between the actual and the predicted WFD compared to the existing models. Besides, the rubberized chip seal performed an enhanced drainage capability compared to conventional chip seal, especially in low slopes, due to the hydrophobic nature of crumb rubber. Accordingly, the proposed model incorporated a term to consider the effect of surface material type.
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