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Effect of pH on the Leaching of Elements from Highway Base Layers Built with Recycled Concrete Aggregates

机译：循环混凝土聚集体基于高速公路基层浸出元素浸出的影响

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Concrete waste is one of the most abundant waste materials, remains in the environment for a long period of time, and if not recycled, can significantly reduce the life of municipal landfill facilities. Crushing waste concrete to make recycled concrete aggregate (RCA) has been gaining more attention recently, as economic and environmental constraints on the production of natural aggregates increase. Recycling concrete also diverts construction and demolition debris waste streams from our landfills. However, RCA has been shown to contain heavy metals which may leach and cause potential contamination of the groundwater. Laboratory pH-dependent batch water leach tests at the pH range of 2-14 were conducted to investigate the leaching behavior of Ca, Zn, and Cu from two different recycled concrete aggregates used in highway constructions. Leached concentrations of Zn were below the detection limits, while the pH of the leachate was higher than 5. Ca showed a cationic leaching pattern, indicating that the concentrations of leached Ca decreased with an increase in pH while Cu and Zn showed amphoteric leaching pattern. The leached element concentrations were below the Environmental Protection Agency Maximum Contaminant Limits (EPA MCLs) with few exceptions. Geochemical modeling results from MINTEQA2 indicated that releases of the elements were solubility-controlled. For a given element, the solubility-controlling solids were found to be very consistent. Oxide and hydroxide minerals control the leaching of Ca, Zn, and Cu elements.
机译：混凝土废物是最丰富的废料之一，在环境中仍然长时间留在环境中，如果没有回收，可以显着减少市政垃圾填埋场的生活。破碎废弃混凝土制作再生混凝土骨料（RCA）最近已获得更多的关注，因为在生产天然骨料的经济和环境约束加大。回收混凝土还从我们的垃圾填埋场转移建筑和拆除碎片废物流。然而，RCA已被证明含有重金属，这可能会浸出并导致地下水的潜在污染。进行了2-14的pH范围的实验室pH依赖性分批水浸出试验，以研究来自公路建设中使用的两种不同再循环混凝土聚集体的Ca，Zn和Cu的浸出行为。浸出的Zn浓度低于检测限，而渗滤液的pH高于5. Ca显示出阳离子浸出图案，表明浸出的Ca的浓度随着CP和Zn的增加而增加，而Cu和Zn显示两性浸出图案。少数例外情况下，浸出的元素浓度低于环境保护局的最大污染物限制（EPA MCLS）。 Minteqa2的地球化学建模结果表明，释放元素的释放控制。对于给定元素，发现溶解度控制固体非常一致。氧化物和氢氧化物矿物质控制Ca，Zn和Cu元素的浸出。

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