Invariant mechanical properties of calcium-silicate-hydrates (C-H-S) in cement-based materials : instrumented nanoindentation and microporomechanical modeling

Random porous solids such as bone and geomaterials exhibit a multiphase composite nature, characterized by water-filled pores of nm- to m-scale diameter. The natural synthesis and operating environments of such materials significantly alters phase composition and multiscale structural heterogeneities throughout the material lifetime, defining significant changes in macroscopic mechanical performance for applications ranging from multispan bridges to calcium-phosphate bone replacement cements. However, the nanoscale phases formed within the unique chemical environment of pores cannot be recapitulated ex situ in bulk form, and imaging of the composite microstructure is obfuscated by the size, environmental fragility, and nonconductive nature of such geomaterials and natural composites. Thus, there is an increasing drive to develop new approaches to image, quantify the mechanical contributions of, and understand the chemomechanical coupling of distinct phases in such composites. In this thesis, we utilize recent advances in experimentation namely instrumented indentation, and micromechanical modeling namely homogenization techniques, in an attempt to quantify the mutli-phase, multi-scale heterogeneity observed in all cement-based materials. We report a systematic framework for mechanically enabled imaging, measuring and modeling of structural evolution for cement based materials (CBM), porous geocomposites, at length scales on the order of constituent phase diameters (10-8 - 10-6 m), and thus identify two structurally distinct but compositionally similar phases heretofore hypothesized to exist.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Constantinides, Georgios, 1978-

Advisor dc:contributor.advisor

• Franz-Josef Ulm.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/34377
• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Identifier URI

http://dspace.mit.edu/handle/1721.1/34377

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/34377