A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
SEM observations of the microstructure of frost deteriorated and self-healed concretes
The microcracking and self healing mechanisms of concrete exposed to rapid freezing and thawing in water and subsequently kept in water have been investigated by Scanning Electron Microscopy (SEM). Non air entrained concretes of water/binder ratio 0.40 with 0 % and 5 % silica fume were studied. Damage was measured as loss on resonance frequency and compressive strength. After frost exposure, concrete beams were stored three months in water. During this time resonance frequency largely recovered, whereas compressive strength showed smaller recovery. On Secondary Electron Images (SEI) of fractured surfaces hydration products mainly of the CaO-SiO2-H2O type were seen traversing cracks at several locations after self healing, but not directly after freeze/thaw. Back Scattered Electron Images (BSEI) showed that the cracks due to freeze/thaw testing were of 1 micron to 10 microns width. The cracks traversed the paste and followed the interfaces of most larger aggregate particles. On BSEI self healing was seen an 300 to 1000 times magnification as partly closing of several cracks smaller than 5 microns. This was most clearly seen by switching between SEI and BSEI modes. In BSEI-mode the re-hydration products appeared less dense and the cracks appeared wider than in the SEI-mode.
SEM observations of the microstructure of frost deteriorated and self-healed concretes
The microcracking and self healing mechanisms of concrete exposed to rapid freezing and thawing in water and subsequently kept in water have been investigated by Scanning Electron Microscopy (SEM). Non air entrained concretes of water/binder ratio 0.40 with 0 % and 5 % silica fume were studied. Damage was measured as loss on resonance frequency and compressive strength. After frost exposure, concrete beams were stored three months in water. During this time resonance frequency largely recovered, whereas compressive strength showed smaller recovery. On Secondary Electron Images (SEI) of fractured surfaces hydration products mainly of the CaO-SiO2-H2O type were seen traversing cracks at several locations after self healing, but not directly after freeze/thaw. Back Scattered Electron Images (BSEI) showed that the cracks due to freeze/thaw testing were of 1 micron to 10 microns width. The cracks traversed the paste and followed the interfaces of most larger aggregate particles. On BSEI self healing was seen an 300 to 1000 times magnification as partly closing of several cracks smaller than 5 microns. This was most clearly seen by switching between SEI and BSEI modes. In BSEI-mode the re-hydration products appeared less dense and the cracks appeared wider than in the SEI-mode.
SEM observations of the microstructure of frost deteriorated and self-healed concretes
Rasterelektronenmikroskopische Beobachtungen an Gefügen von frostgeschädigten und selbstausheilenden Betonen
Jacobsen, S. (author) / Marchand, J. (author) / Hornain, H. (author)
Cement and Concrete Research ; 25 ; 1781-1790
1995
10 Seiten, 6 Bilder, 3 Tabellen, 24 Quellen
Article (Journal)
English
SEM Observations of the Microstructure of Frost Deteriorated and Self-Healed Concretes
| Online Contents | 1995
SEM Observations of the Microstructure of Frost Deteriorated and Self-Healed Concretes
| British Library Online Contents | 1995
Microstructure of Steam Cured Concretes Deteriorated by Alkali-Silica Reaction
| British Library Conference Proceedings | 1995
Microstructural investigation of deteriorated Portland cement concretes
| Online Contents | 1996
Microstructural investigation of deteriorated Portland cement concretes
| British Library Online Contents | 1996