The Nanogranular Behavior of C-S-H at Elevated Temperatures (up to 700 °C)

Cement-based materials are non-combustible, but the complex chemo-physical mechanisms that drive the thermal degradation of the mechanical properties (stiffness, strength) at elevated temperatures are still an enigma that have deceived many decoding attempts. This paper presents, for the first time, results from a new experimental technique that allows rational assessment of the evolution of the nano-mechanical behavior of cement paste at elevated temperatures. Specifically, the thermal degradation of the 2 distinct calcium-silicate hydrate (C-S-H) phases, Low Density (LD) C-S-H and High Density (HD) C-S-H, is assessed based on a statistical analysis of massive nanoindentation tests. From a combination of nanoindentation, thermogravimetry, and micromechanical modeling, a new mechanism is identified--the thermally induced change of the packing density of the 2 C-S-H phases, as the dominant mechanism that drives the thermal degradation of cementitious materials. It is argued that this loosening of the packing density results from shrinkage of C-S-H nanoparticles that occurs at high temperatures, most likely due to loss of chemically bound water.

Availability:
- Find a library where document is available. Order URL: http://worldcat.org/issn/00088846
Supplemental Notes:
- Abstract reprinted with permission from Elsevier
Authors:
- DeJong, Matthew J
- Ulm, Franz-Josef
Publication Date: 2007-1

Language

English

Media Info

Media Type: Print
Features: Figures; References; Tables;
Pagination: pp 1-12
Serial:
- Cement and Concrete Research
- Volume: 37
- Issue Number: 1
- Publisher: Elsevier
- ISSN: 0008-8846
- Serial URL: http://www.sciencedirect.com/science/journal/00088846

Subject/Index Terms

TRT Terms: Cement paste; Concrete construction; Concrete structures; Fire; Granular materials; High temperature; Mechanics; Packaging; Thermal degradation; Tunnels
Subject Areas: Bridges and other structures; Design; Freight Transportation; Highways; I25: Design of Tunnels;

Filing Info

Accession Number: 01042257
Record Type: Publication
Files: TRIS
Created Date: Feb 26 2007 2:32AM