QUALITY INSPECTION OF 3D PRINTED CONCRETE ELEMENTS USING TERRESTRIAL LASER SCANNING

Abstract

Concrete three-dimensional (3D) printing technology, a form of additive manufacturing process, has been gaining attention within the Architectural, Engineering and Construction (AEC) industry due to the significant benefits it brings. As the construction industry in Singapore is heavily reliant on manpower and known for its low productivity, many efforts are in place to explore the use of 3D concrete printing technology to boost construction productivity and promote sustainability. Traditionally, quality inspections of concrete structures are conducted manually by inspectors using measuring tapes, straight edges and checklists which can be subjective, time-consuming, unreliable and prone to errors. In recent years, quality inspection of concrete structures through Terrestrial Laser Scanning (TLS) technology has been proven to be promising as it is capable of acquiring data of higher accuracy and spatial data density which can overcome the limitations of current inspection process. Nonetheless, research studies have mostly outlined the feasibility of using TLS for quality inspections on reinforced concrete and precast concrete elements. With 3D concrete printing technology known to be up-and-coming in the construction industry globally, this study aims to investigate the effectiveness of adopting TLS technology for inspection of 3D concrete printed elements and differences between high and low scanning resolution. As there are no specific quality inspection checklists for 3D concrete elements available in the industry at the time this research was conducted, references to two different industry practices and standards were made in order to develop a quality inspection checklist for the evaluation of the experiment subject. Based on results of this study, it is recognized that such technology is promising as it provides the ability to conduct measurements ranging from as small as millimetres which is evidently more precise than manual inspection measurement tools. To ensure an accurate quality inspection where measurements are of the highest accuracy, results suggest that higher scanning resolution is required as it increases the accuracy and number of scanned data points which reduces variation of measurements. In addition, it is also discovered that point cloud data is greatly influenced by the occurrence of mixed-pixel effect caused by position of laser scanners.