This study aims to enhance the utilization rate of recycled concrete aggregate (RCA) in structural concrete through the application of a novel carbonation treatment method to improve the microstructure of old adhered mortar in RCA and enhance its compatibility with the new concrete. Carbonation of RCA is a commonly used method to densify the microstructure of old adhered mortar, but it exhibits limitations due to the low available calcium content in RCA for reacting with CO₂. To address this, a novel approach by coating the RCA with blast furnace slag before subjecting it to carbonation was proposed. This involves two key benefits: (1) it introduces external calcium, thereby increasing the CaCO₃ content after carbonation and densifying the microstructure, and (2) it provides silica, facilitating a pozzolanic reaction that enhances bonding with new concrete. The effectiveness of pressurized and wet carbonation methods was evaluated and compared in the research. Following carbonation of the slag-coated RCA, the microstructure densification and improvement in interfacial properties between RCA and new cement paste were assessed through water absorption and slant shear test, respectively. The underlying mechanism was investigated by TGA, XRD, and SEM-EDS. The findings indicate that slag coating significantly enhances microstructure densification, reducing water absorption by up to 40 % and increasing bond strength by up to 65 % after carbonation. Pressurized carbonation enhances CO₂ penetration and dissolution in RCA, increasing CaCO₃ production and improving the microstructure. It also produces more needle-like aragonite, strengthening the bond between RCA and new concrete.

中文翻译：

---

通过矿渣涂层碳化增强再生混凝土骨料


本研究旨在通过应用新型碳化处理方法提高再生混凝土骨料 （RCA） 在结构混凝土中的利用率，以改善 RCA 中旧粘附砂浆的微观结构并增强其与新混凝土的相容性。RCA 的碳化是致密化旧粘附砂浆微观结构的常用方法，但由于 RCA 中与 CO₂ 反应的可用钙含量低，因此存在局限性。为了解决这个问题，提出了一种在碳化之前用高炉炉渣涂覆 RCA 的新方法。这涉及两个主要好处：（1） 它引入外部钙，从而增加碳化后的 CaCO₃ 含量并致密化微观结构，以及 （2） 它提供二氧化硅，促进火山灰反应，增强与新混凝土的结合。在研究中评估和比较了加压和湿式碳酸化方法的有效性。在矿渣涂层 RCA 碳化后，分别通过吸水和斜剪切试验评估了 RCA 和新型水泥浆体之间的微观结构致密化和界面性能的改善。通过 TGA 、 XRD 和 SEM-EDS 研究了其潜在机制。研究结果表明，矿渣涂层显著增强了微观结构致密化，碳化后吸水率降低高达 40%，粘结强度提高高达 65%。加压碳化增强了_CO2 在 RCA 中的渗透和溶解，增加了 CaCO₃ 的产生并改善了微观结构。它还会产生更多的针状文石，加强 RCA 和新混凝土之间的粘合。