Evaluation of reinforced concrete structural durability in the post-occupation phase - A case study in Novo Hamburgo/RS

Abstract Researches on building performance have been developed over time. The Brazilian Performance Standard - NBR 15575 - deals with the issues of durability applied to residential buildings, establishing criteria and parameters to classify the systems into minimum, intermediate and higher performance levels. In relation to the service life, studies are also associated with the building’s structural durability, in which the technical specifications and quality of materials, construction systems, building process, use and maintenance of the building are important factors for better performance. In order to evaluate the structural durability over the years, a case study was conducted in a building designed to meet the higher level established in the Brazilian Performance Standard, with service life of 75 years in the structural project, through the non-destructive surface hardness of concrete test by using a Schmidt hammer and semi-destructive carbonation tests. The superficial hardness test was conducted on a concrete column following the procedures of NBR 7584, while the carbonation samples were collected in 3 concrete columns in which a phenolphthalein solution was sprayed to observe the alkalinity of the samples. For all tests, three different heights were considered. The concrete testing hammer indicated an average surface hardness of approximately 50 MPa, and for carbonation tests, it was noted that the concrete was not carbonated at a depth of 5mm. So, the criteria of service life could be considered attended.

摘要 建筑性能研究随时间推移不断深化。巴西建筑性能标准NBR 15575针对住宅建筑耐久性相关问题作出规范，确立了将建筑体系划分为最低、中等及高性能等级的判定准则与参数指标。就建筑使用寿命而言，相关研究亦与建筑结构耐久性紧密相关，其中材料技术规格与质量、施工体系、建造流程、建筑使用及维护等因素，均对建筑性能优劣具有重要影响。为评估建筑长期结构耐久性，本研究针对一座符合巴西建筑性能标准高性能等级的建筑开展案例研究，该建筑结构设计使用寿命为75年。测试采用回弹仪（Schmidt hammer）开展混凝土表面硬度无损检测，以及半破坏性碳化试验。混凝土表面硬度测试依照NBR 7584标准在一根混凝土柱上开展；碳化试验则在3根混凝土柱上取样，通过喷涂酚酞溶液（phenolphthalein solution）观测试样的碱度变化。所有测试均选取三个不同高度位置开展。回弹仪检测结果显示，混凝土表面平均硬度约为50 MPa；碳化试验则表明，该混凝土在5mm深度范围内未发生碳化。由此可见，该建筑满足使用寿命相关准则要求。