Characterization of Ultrahigh-Performance Concrete Materials for Application in Modular Construction

AbstractIn this paper, a new class of self-consolidating ultrahigh-performance concrete (UHPC) was investigated. The UHPC featured a compressive strength higher than 150 MPa with self-consolidating characteristics desirable for modular construction. This paper describes the development and characterization of UHPC, its large-scale processing techniques with conventional equipment, its verification with internal and surface microstructure analysis techniques, and the structural behavior of large-scale steel plate UHPC (S-UHPC) beams under out-of-plane loads. Based on a particle size distribution study, an optimum packing density was achieved in the mixture that uses an uncommonly used undensified silica fume. The physical parameters of the ingredients and the resulting microstructure after hydration are considered essential for the design of self-consolidating UHPC materials. Distinguishing the three phases of the material after hydration using three-dimensional X-ray microtomography allowed the quantitative analysis of the UHPC microstructure. The internal microstructure study showed a significant reduction of macropores in UHPC compared to mortar specimens, which confirmed the physical attributes behind the improved material characteristics. A microstructure study of the material was also performed using scanning electron microscopy. In addition, a comparison of the experimental results of four large-scale steel plate concrete (SC) beam specimens cast with either conventional concrete or UHPC materials under three-point shear loading indicated that the developed UHPC materials significantly enhanced the ductility and capacity of the S-UHPC beams.