Advanced characterization of cold asphalt patching materials in repairing road pavement potholes and cracks

Abstract

Cold mixed patching materials (CMPM) consist of a combination of aggregates with special binders and additives that are commonly used for repairing potholes, cracks, and small-scale patches in road pavements when the outside temperature is too cold for applying hot mix asphalt. Although these affordable products have a short application time and less environmental impact, they often associate with several defects and drawbacks, such as raveling, water sensitivity, poor bonding, workability, and stability. Among all patch materials, CMPMs have the lowest quality and usually offer relatively poor mechanical and functional performance in the field. Repaired potholes during adverse weather conditions, especially in wet winters and springs, withstand only a few freeze-thaw cycles and are sometimes physically removed even by the first traffic actions. If the CMPM used to repair potholes is of high quality and is correctly applied, it can last longer. However, there aren't any global standards or guidelines for evaluating the performance of these materials, thereby determining their quality. Therefore, in this research specific laboratory test methods and procedures, including Marshall stability, indirect tensile strength, Hubbard-Field stability, indentation stability, shear bond, locking point, and brush test, were proposed to provide a tool for advanced technical analysis of the expected performance of CMPMs in practice and better-specialized production for different climates and usage conditions. Different types of CMPMs available on the market, belonging to three main CMPM categories, including solvent-containing mixtures (SC), membrane-containing mixtures (MC), and water-reactive mixtures (WR), were selected and characterized using the mentioned procedures to qualify their performance in pothole repair operations and to observe the performance of test methods and approaches on the materials. In addition, a field study was set up by making potholes and filling them with different materials using manual and machine compacting strategies to investigate the performance of CMPMs in patching operations. The laboratory findings showed that the proposed test methods led to more reasonable and reliable outcomes compared to the currently used procedures. In every test, WR materials performed far better than other mixtures. Among all materials, the SC material performed the least well. Although the field results occasionally conflicted with the laboratory findings, they nevertheless demonstrated that even poorly evaluated materials in the laboratory last longer when the proper application repair procedure is applied. Moreover, the workability and compactability of the mixtures were more decisive factors in providing the durability of the patches compared to other properties.