Abstract
This paper studies the evolution of elastic and thermal properties of cementitious composites containing micro-size lightweight fillers after exposure to elevated temperatures (up to 800 °C). A multiscale investigation is carried out to study the thermal degradation of cementitious composite materials at multiple scale levels: at cement past level, the dehydration kinetics of cement hydrates (i.e., C–S–H, CH and aluminate hydrates) and development of microcracks are studied as functions of exposure temperatures. The damage mechanism of the inclusion phases and damages within the interfacial transition zone (ITZ) under elevated temperature are also investigated. In addition, the change of mechanical (i.e., elastic moduli, compressive strengths) and thermal (thermal conductivities) properties are measured as functions of the exposure temperature. Based on the experimental studies, a multiscale thermal degradation model is developed where the thermal degradations of cement paste (including water composition, porosity, and solid phase changes), inclusion phases, and the interfaces are captured through a multiscale sub-stepping homogenization scheme. The thermal degradation model is validated through multiple sets of experimental data. Finally, the influence of key parameters including the particle size distribution of the inclusions, the chemical composition, as well as the effects of ITZ damage are studied.
Original language | English |
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Article number | 103931 |
Journal | Cement and Concrete Composites |
Volume | 118 |
DOIs | |
State | Published - Apr 2021 |
Externally published | Yes |
Funding
This research is sponsored by US Department of Energy Building Technology Office (DOE Grant# DE-EE0008677 ) and US National Science Foundation (NSF Grant# CMMI-1663302 , CMMI-1954517 ). The funding supports from DOE and NSF are greatly appreciated. The author would like to thank Mr. Yi Fang for his assistance to conduct the SEM analysis and Dr. Mansoureh Norouzi Rad from Carl Zeiss Microscopy for performing the X-ray microtomography (XRM) analysis.
Keywords
- Cementitious composites
- Lightweight fillers
- Micro-mechanics model
- Thermal damage