There are concerns about the potential toxicity of bitumen and recycled materials such as reclaimed asphalt pavements from end-of-life roads and crumb rubber from scrap tires used in asphalt mixtures because they contain metals that may be released into the groundwater. This study investigated the potential metal leaching of laboratory-prepared asphalt mixtures modified with polymer coated rubber (PCR) with wet and dry technology, devulcanized rubber (DVR), compared to an unmodified control mixture and a blend modified with a synthetic polymer (SBS). The objectives were to i) quantify concentrations of metals released, ii) calculate the flux rate, the cumulative mass release, and the assessment ratio for each metal, iii) verify if the metals exceeded the EPA drinking water limit, and, finally, iv) assess the source of metals release. Zinc had the highest concentration among all metals and was present in eluates from all mixtures. The cumulative zinc concentration from DVR mixture was 41% and 34% higher than the control and SBS mixtures, respectively. For PCR wet, the cumulative zinc concentration was 9% higher than the control blend and 1% lower than the SBS mix. The assessment ratio indicated that all metal concentrations would not exceed the drinking water limit, except for zinc, for which further evaluations were required. The main source of zinc may derive from aggregates. This work showed that crumb rubber might not be the only source of metal leaching, and its use in asphalt pavements does not cause a metal leaching higher than other materials.

中文翻译：

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废旧轮胎胶粉改性沥青混合料中金属的浸出行为

人们担心沥青和再生材料的潜在毒性，例如来自报废道路的再生沥青路面和沥青混合物中使用的废轮胎的碎橡胶，因为它们含有可能释放到地下水中的金属。本研究调查了实验室制备的沥青混合料的潜在金属浸出，该沥青混合料采用湿法和干法技术的聚合物涂层橡胶 (PCR) 改性，脱硫橡胶 (DVR) 与未改性的对照混合物和合成聚合物 (SBS) 改性的共混物进行了比较。目标是 i) 量化释放的金属浓度，ii) 计算每种金属的通量率、累积质量释放和评估比率，iii) 验证金属是否超过 EPA 饮用水限值，最后，iv ) 评估金属释放的来源。锌在所有金属中浓度最高，并且存在于所有混合物的洗出液中。 DVR 混合物的累积锌浓度分别比对照和 SBS 混合物高 41% 和 34%。对于 PCR 湿法，累积锌浓度比对照混合物高 9%，比 SBS 混合物低 1%。评估比例表明，除锌外，所有金属浓度均不会超过饮用水限值，需要进一步评估。锌的主要来源可能来自骨料。这项工作表明，胶粉可能不是金属浸出的唯一来源，并且其在沥青路面中的使用不会导致比其他材料更高的金属浸出。