Canadian Geotechnical Journal, Ahead of Print.
Recycled concrete aggregate (RCA) can be used in landfill and slope cover systems, where its unsaturated hydraulic properties play an important role. The hydraulic behavior of RCAs can be potentially controlled through mixing coarse and fine aggregates by a pre-determined proportion, which lacks experimental validation. In this study, water retention curve (WRC) and permeability function (PF) of RCAs with different fine aggregate contents (fc) were investigated. Experiments on 9 RCAs with different gradations reveal that when fc is between 20% and 30%, a second air entry value appears, and the shape of both WRC and PF becomes bimodal, which is probably resulted from an uneven dual-peak pore size distribution. With an increasing fc, the first air entry value and the residual water content increases. The unsaturated coefficient of permeability decreases with the increasing fc for a low suction level (<0.1 kPa), but increases with the raise of fc for high suction (>10 kPa). Overall, adopting a properly mixed RCA with fc value of less than 10% or over 40%, instead of a narrowly graded RCA, is recommended for coarse- and fine-grained layers in a capillary barrier, respectively.

中文翻译：

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细骨料掺量对再生混凝土骨料不饱和水力特性的影响

加拿大岩土工程杂志，印刷前。
再生混凝土骨料（RCA）可用于垃圾填埋场和坡面覆盖系统，其不饱和水力特性发挥着重要作用。RCA 的水力行为可以通过按预定比例混合粗骨料和细骨料来控制，但缺乏实验验证。在这项研究中，研究了不同细骨料含量（fc）的RCA的保水曲线（WRC）和渗透函数（PF）。对9个不同级配RCA的实验表明，当fc在20%~30%之间时，出现第二个进气值，WRC和PF的形状都变成双峰，这可能是由于双峰孔径分布不均匀造成的。随着fc的增加，首次空气进入值和残余水含量增加。对于低吸力（<0.1 kPa），不饱和渗透系数随着fc的增大而减小；对于高吸力（>10 kPa），不饱和渗透系数随着fc的增大而增大。总体而言，对于毛细管屏障中的粗粒层和细粒层，建议分别采用 fc 值小于 10% 或超过 40% 的适当混合的 RCA，而不是窄分级的 RCA。