The proposed research focuses on high temperature effects related to fire safety. The project includes (a) high temperature experiments on concrete specimens with different w/c ratio ranging from normal to high performance (low permeability) concretes, and (b) computational simulations of interacting mechanical and environmental degradation processes at the macro- and meso-scales of observation. The multi-scale methodology will employ micro-mechanics of multi-phase materials at the level of the hardened cement paste and local-global finite element strategies to model and upscale the heterogeneous meso-structure of concrete where aggregate particles are interacting with a contiguous cement paste through cohesive interface elements of zero-thickness. Applications will include studies of the fire resistance of concrete specimens, which are subjected to high temperature fire scenarios and simultaneous mechanical loading. A number of fundamental questions will be addressed, starting from transitional thermal creep effects under variable temperatures, to pore pressure- vs humidity-driven thermal shrinkage, as well as micro-mechanical processes of composite damage considering coupling between thermal and mechanical degradation. The numerical simulator will provide a tool to design and optimize the constituents of concrete and to assess vulnerability of the nation's concrete infrastructure against fire hazards. The numerical simulation platform will be used as an educational tool in a new undergraduate materials course that will be offered in the Civil Engineering Program at the University of Colorado. The PC-based concrete simulator will also serve as a demonstration tool for public outreach, especially to high school teachers and K-12 students, on material awareness taking advantage of the new Integrated Teaching and Learning Laboratory at the University of Colorado which has received national attention because of its novel approach to learning through discovery. The numerical concrete simulator will be disseminated through a web site which will document the progress and outcome of model-based material simulation software for concrete and particulate composites in general.
