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Cold mix recycled asphalt (CMRA) concrete was evaluated to be an innovative repair material to improve the pavement quality and environmental impact on pipeline maintenance in this study. The study presented and specifically examined the use of CMRA with 2.5 % foam asphalt content as a replacement for the currently used controlled low-strength material (CLSM) as pipeline backfill material. CMRA’s material properties, performance, carbon dioxide emissions, cost, and construction time were analyzed in this study to confirm the advantages and limitations of CMRA. The results concluded that CMRA performed better than CLSM for all the items analyzed. Specifically, according to the performance analysis, CMRA exhibited a better Marshall stability index, California bearing ratio, indirect tensile strength, tensile strength ratio, anti-rutting ability, and penetration than the standards specified. Furthermore, the average carbon emissions of CMRA were 36 % less than CLSM, could save at least 2 h of construction time per cubic meter of construction, and immediately opened traffic. However, CRMA’s construction cost in this study was similar to CLSM and was only lower (up to 2.3 %) by considering a similar price of cement, asphalt, and additives. Based on the aforementioned results, this study concluded that the findings may be of particular interest for Taiwanese pipeline maintenance projects as a backfill material and is worthy of further research.

Toughness, as defined in ASTM D5801, is the work used to stretch a specimen until fracture, and is used to evaluate the ability of polymer modified asphalt (PMA) to resist deformation. Fracture elongations in PMA are usually longer than 10 cm. However, it is almost impossible for asphalt concrete, with or without PMA, to endure such large deformation before fracture. It is presumed that an effective elongation exists for more effective determination of toughness. Principle component analysis (PCA) and single regression analysis were used in this study to evaluate the correlation between physical tests of PMA, including toughness and performance tests of Stonic Mastic Asphalt (SMA). Meanwhile, performance tests, including resilient modulus tests, creep tests and indirect tensile tests, were conducted on SMA samples. According to the results form Principle Components Analysis (PCA), it was observed that only a common factor affects the performance tests. Regression analyses were used to find common factors from physical tests of PMA. Correlation coefficients between toughness and performance tests were found to be better than other physical tests. When toughness was calculated with effective elongation (6.5 cm), R 2 was 0.90. In our opinion, the desirable PMA should provide SMA enough work to resist the deformation while the deformation is still small. This result was also confirmed by observation of SEM and Rheological analysis. Modified toughness (calculated with effective elongation) considered as the common factor, is a simple method to evaluate the microstructure of PMA. Overall, modified toughness seems promising for use in evaluation of the effect of PMA on SMA.