Visualization of Macroscopic Structure of Ultra-high Performance Concrete Based on X-ray Computed Tomography Using Immersive Environments

Abstract

Ultra-high performance concrete (UHPC) is a cementitious composite material which uses steel fibers, cement, silica fume, fly ash, water, and admixtures to provide better structural performance and durability compared to conventional concrete. UHPC is an attractive novel material because of its higher compressive strength, higher tensile capacity, and ultralow permeability. Currently in the United States, UHPC is batched in smaller quantities on-site with very strict quality control by representatives from the producer. This has significantly increased the cost (more than 15 times higher) of poured UHPC compared to conventional concrete. It is not studied if substituting the representatives from a commercial producer with trained concrete technicians from public and other entities, would actually yield into substantial defects in the structure of poured UHPC. Similar to conventional concrete, mechanical properties of UHPC, a heterogeneous material from various structural scales (microscopic, mesoscopic, and macroscopic) is expected to be different from each other. Past research has shown that defects that exist on smaller scales can dictate the performance of UHPC overtime. However, macroscopic structural analysis may be the most effective method to capture the defects and uncertainties due to quality of on-site workmanship. This research focuses on the X-ray computed tomography (XCT) of macroscopic structures. XCT is an effective analysis tool for structural components (e.g., beam, columns, walls, slabs) in civil and critical infrastructures. This paper presents a detailed overview outlining how the macroscopic structure of concrete characterized by XCT can be visualized in an immersive environment using virtual reality while capturing and recording the details of a scanned object for both current and future analysis. The high resolution two dimensional (2-D) tomographic slices, and 3-D virtual reconstructions of 2-D slices with subsequent visualization, can represent a spatially accurate and qualitatively informative rendering of the internal structure of UHPC components poured by individuals who are not necessarily representatives of a commercial producer. Results from this research are expected to reduce the cost of UHPC by modifying the guidelines for on-site pour. This can contribute to wider adoption of UHPC in future projects.