Evaluation of foam concrete physical properties and mechanical response under indentation
Lightweight foam concrete is a widely accepted construction material with a controllable low strength. Conventional use of this material is often seen in applications such as excavatable landfilling or thermal isolation. Different from solid material, this cellularized cementitious foam tends to exhibit extensive plastic deformation when loaded to failure, accompanied by considerable energy dissipation. Taking advantage of this crushable nature, a novel usage of foam concrete is found in impact-absorbing applications. Unlike structural concrete, the functional application of foam concrete also shows good feasibility for accommodating high-volume recycled fine particles. This potential brings a promising prospect to pursue the green engineering concept with foam concrete. However, the implementation of this material as an energy absorber is awaiting a more in-depth investigation of its key material attributes to the mechanical especially crushing performance. In this dissertation, several critical aspects of the mechanical performance of lightweight foam concrete are investigated using a series of advanced characterization techniques, as well as computational approaches. The elastic modulus of foam concrete is measured via a nondestructive vibrational frequency test. The crushing behavior is characterized based on the load-displacement response in a penetration test. Build on these, further attention is paid to the foam densification phenomenon using correlation analysis, digital image correlation (DIC), and X-ray computed tomography (CT). The material failure process of foam concrete is explained based on the experimental observations. A constitutive relationship is further established for elaborating the relationship between foam densification and mechanical performance. Using the measured material properties, the crushing behavior of foam concrete is investigated using a smoothed particle hydrodynamic (SPH) simulation, where good agreements with the experimental observations are obtained. Subsequently, a more complex crushing scenario is investigated, in which an aircraft wheel crushing on a lightweight foam concrete pavement is modeled. This simulation yields a realistic prediction of the arresting performance of the engineered material arresting system (EMAS) made of foam concrete during an overrun. With respect to the fine particle inclusion in foam concrete, its effect on different properties of foam concrete is investigated, which primarily includes foam geometry, fundamental frequency, elastic modulus, crushing response, compressive strength, as well as drying shrinkage. As a side project of this Ph.D. study, two featured studies on concrete petrographic analysis are also included in this dissertation. The first one is using deep learning-based concrete image segmentation. The second is predicting the 3D concrete freeze-thaw protection based on 2D imaging.
foam concrete, cellular concrete, solid foam, mechanical property, crushing, energy absorption, impact absorption
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign