Fire Performance of Sustainable Recycled Concrete Aggregates: Mechanical Properties at Elevated Temperatures and Current Research Needs

The materials used for the construction of buildings are changing. There are now many sustainability drivers for developing novel green construction materials. An emerging material used for building construction is concrete with conventional coarse aggregates substituted as recycled concrete aggregates (RCA). This is a form of sustainable concrete. A finite number of buildings (> 10) with this material have been constructed in North America, Europe and Asia. However; to help facilitate wide spread use and development of sustainable concrete with RCA, there is purpose in considering this material's at-elevated temperature (in-fire) mechanical properties. To date, this topic has seen limited research attention as it is difficult to study. The study herein considered the mechanical properties of conventional and sustainable concrete with RCA. The only difference between the conventional and the sustainable concrete mixes was the mass proportion of a conventional natural coarse aggregate, Limestone, which had been substituted with coarse RCA (at replacement proportions of 0%, 30% and 100%). Both the ambient and elevated temperature mechanical properties were considered with compressive mechanical tests using an innovative optical technology for strain measurement. Based on the analysis performed, a proportional decrease in retained strength and elasticity of concrete at-elevated temperature with increasing RCA content was observed. For example both mechanical properties showed a 0.2% decrease in retained value for every 1% RCA increase at 500A degrees C. In addition the modelling parameter of Poisson ratio appeared to be influenced by the heat imposed and the aggregate type contained within the concrete. For example at 500A degrees C, this parameter showed an 73% increase for concrete samples with only Limestone aggregate and a 15% decrease for samples with only RCA (of mixed origin primarily Siliceous). This paper concludes with highlighting current knowledge gaps and research needs that when addressed could help improve the facilitation of using sustainable concrete's with RCA in construction of buildings.

建筑施工所用的材料正在发生变化。如今，开发新型绿色建筑材料有许多可持续性驱动因素。一种用于建筑施工的新兴材料是用再生混凝土骨料（RCA）替代常规粗骨料的混凝土。这是一种可持续混凝土。在北美、欧洲和亚洲已经建造了数量有限（>10座）的使用这种材料的建筑。然而，为了有助于促进含RCA的可持续混凝土的广泛使用和开发，考虑这种材料在高温（火灾中）下的力学性能是有意义的。到目前为止，由于该主题难以研究，所以受到的研究关注有限。本文研究考虑了含RCA的常规混凝土和可持续混凝土的力学性能。常规混凝土和可持续混凝土混合物之间的唯一区别是常规天然粗骨料石灰石的质量比例，它被粗RCA所替代（替代比例分别为0%、30%和100%）。通过使用一种创新的应变测量光学技术进行压缩力学试验，考虑了常温及高温下的力学性能。根据所进行的分析，观察到随着RCA含量的增加，混凝土在高温下的剩余强度和弹性成比例下降。例如，在500℃时，每增加1%的RCA，两种力学性能的剩余值都会下降0.2%。此外，泊松比的建模参数似乎受到所施加的热量以及混凝土中所含骨料类型的影响。例如，在500℃时，仅含石灰石骨料的混凝土样品的该参数增加了73%，而仅含RCA（主要为硅质混合来源）的样品则下降了15%。本文最后强调了当前的知识空白和研究需求，解决这些问题可能有助于促进在建筑施工中使用含RCA的可持续混凝土。