Žurauskienė Ramunė, Valentukevičienė Marina
Department of Building Materials and Fire Safety, Faculty of Civil Engineering, Vilnius Gediminas Technical University, LT-10223 Vilnius, Lithuania.
Department of Environmental Protection and Water Engineering, Faculty of Environmental Engineering, Vilnius Gediminas Technical University, LT-10223 Vilnius, Lithuania.
Materials (Basel). 2020 Jun 3;13(11):2538. doi: 10.3390/ma13112538.
Concrete itself, and issues relating to the recycling and management of reinforced concrete waste, are highly relevant, especially when urban expansion is being achieved by increased building construction volumes. This research investigates concrete waste and its (re)usage possibilities and resolves several major issues related to the question of how natural materials can be replaced by compounds made from concrete waste, thereby saving natural resources. The experiment was carried out using concrete mixtures, which were combined with natural aggregates and crushed concrete waste (fraction 4/16). The resulting mix of concrete was achieved using natural aggregates, thus replacing natural aggregates with waste, which had partially and fully replaced bulky aggregates with crushed concrete waste. The main aim of the investigation was to investigate how aggregates made from crushed concrete waste impact the properties of concrete. The exothermic effect on the concrete mixture during the hardening process was investigated. Furthermore, a macrostructural analysis of hardened concrete was conducted using scanned sample images; the adhesion zone between newly formed concrete stone and aggregates derived from natural rock from crushed concrete waste was investigated. Using an electron microscope to observe aggregate from crushed concrete waste and the contact zone of hardened cement stone revealed that the aggregate from waste adheres poorly with hardened cement stone. Furthermore, both the mechanical properties of new, hardened concrete and determined resistance to frost indicators are weak. Concrete density and compression strength decreased (by up to 8% and up to 18%, respectively), and absorption increased almost twofold due to aggregates derived from crushed concrete waste, since their cleavage strength indicator was twice as high, while water absorption was four times higher than that of natural aggregate. The results indicate that recycled concrete obtained from demolished buildings is environmentally sustainable and can be recommended for lower quality concrete for use in related engineering projects.
混凝土本身以及与钢筋混凝土废料的回收和管理相关的问题具有高度相关性，尤其是在通过增加建筑施工量来实现城市扩张的时候。本研究调查了混凝土废料及其（再）利用可能性，并解决了几个与如何用混凝土废料制成的化合物替代天然材料从而节约自然资源这一问题相关的主要问题。实验使用了混凝土混合物，将其与天然骨料和破碎混凝土废料（4/16 级配）混合。最终的混凝土混合物是使用天然骨料制成的，从而用废料替代天然骨料，其中破碎混凝土废料部分或全部替代了大块骨料。该调查的主要目的是研究由破碎混凝土废料制成的骨料如何影响混凝土的性能。研究了硬化过程中对混凝土混合物的放热效应。此外，利用扫描样本图像对硬化混凝土进行了宏观结构分析；研究了新形成的混凝土石与来自天然岩石的破碎混凝土废料骨料之间的粘结区域。使用电子显微镜观察破碎混凝土废料的骨料和硬化水泥石的接触区域发现，废料骨料与硬化水泥石的粘结性较差。此外，新的硬化混凝土的力学性能和确定的抗冻指标都较弱。由于来自破碎混凝土废料的骨料，混凝土密度和抗压强度分别降低了（高达 8%和高达 18%），吸水率几乎增加了一倍，因为它们的劈裂强度指标是天然骨料的两倍，而吸水率是天然骨料的四倍。结果表明，从拆除建筑物中获得的再生混凝土在环境方面是可持续的，可推荐用于相关工程项目中质量要求较低的混凝土。
