OPTICAL MICROSCOPY
At the Heart of Our Examinations
PROCEDURES
Procedures for petrographic examinations are described in the following ASTM standard practices & test methods, which are the core tests that the optical microscopy laboratory of CMC conducts:
• ASTM C 295 - Aggregates
• ASTM C 457 - Air void Analysis in Hardened Concrete
• ASTM C 856 - Petrographic Examinations of Concrete
• ASTM C 1324 - Petrographic Examinations of Historic & Modern Masonry Mortars
• ASTM C 1721 - Petrographic Examination of Dimension Stone
EQUIPMENTS USED
A large collection of optical microscopes - from antique to latest advanced microscopes from Nikon, Olympus, Leitz, Leica, Zeiss, Unitron, Busch and Lomb, etc. to various digital microscopes, and, photomicrographic equipments
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Low-power Stereozoom microscopes
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Low to high-power reflected and transmitted-light Stereozoom microscopes
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Petrographic microscopes having facilities for
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Transmitted-polarized light (for plane and crossed-polarized light observations of a thin section),
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Reflected-light (for examination of a polished thin or solid section), and
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Epi-fluorescent light (for examination of a fluorescent thin section);
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Metallurgical microscopes for examination of polished solid samples
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Phase contrast microscopes
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USB microscopes
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Air-void analysis by two Stereozoom microscopes attached to stepper-motor controlled X-Y stages and air-void analysis software
Each petrographic workstation is equipped with
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A petrographic microscope, having reflected and transmitted polarized lights, and, transmitted or reflected (epi) fluorescent light facilities
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A low-power stereo-microscope (Nikon, Olympus, Zeiss, Leitz) or a metallurgical microscope (Leitz and Zeiss).
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All microscopes have digital cameras (Jenoptik Progres C3, C7, C10, C14 series, and Gryphax, OMAX, Infinity Lumenera series, Leica, Basler Ace, Moticam, etc.), PC or Mac, and associated software for image acquisitions.
Workhorse optical microscopes used for day-to-day projects of CMC.
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Left = Nikon Eclipse E600 POL petrographic microscope having transmitted polarized, reflected polarized, and fluorescent light facilities; connected to a Jenoptik Progres Gryphax camera.
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Top Middle to Right = Nikon SMZ-10A Stereozoom microscope, Olympus SZH Stereozoom microscope having reflected and transmitted polarized light facilities – both connected to a Lumenera Infinity camera, Nikon Labophot 2 POL, and Nikon SMZ-2T Stereozoom microscope.
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Bottom Middle to Right = USB digital microscope, Busch & Lomb Stereozoom 7 microscope, Nikon Labophot 2 POL petrographic and ore (reflected-light) microscope, and Nikon Optiphot 2 phase contrast and transmitted fluorescent light microscope - all connected to PC by respective digital cameras from 6MP to 14MP resolutions.
Different optical microscopes used in CMC optical microscopy lab - from low to medium power stereozoom microscope to polarizing and petrographic microscopes to metallurgical microscopes to comparison microscopes to fluorescent microscopes.
"For the limits to which our thoughts are confined, are small in respect of the vast extent of Nature itself; some parts of it are too large to be comprehended and some too little to be perceived. And from thence it must follow, that not having a full sensation of the Object, we must be very lame and imperfect in our conceptions about it, and in all the propositions which we build upon it; hence we often take the shadow of things for the substance, small appearances for good similitudes, similitudes for definitions; and even many of those which we think to be the most solid definitions, are rather expressions of our own misguided apprehensions then of the true nature of the things themselves. .....by the help of Microscopes, there is nothing so small, as to escape our inquiry; hence there is a new visible World discovered to the understand….By this the Earth it self, which lyes so near us, under our feet, shows quite a new thing to us, and in every little particle of its matter, we now behold almost as great a variety of Creatures, as we were able before to reckon up in the Whole Universe it self….” Robert Hooke, in Micrographia ,1665 [the first "microscope book"]
A wide variety of photographic equipments from flatbed scanner to digital cameras to slide scanners are used during petrographic examinations to collect photographs and photomicrographs of samples at various stages.
CONCRETE UNDER MICROSCOPE
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MASONRY UNDER MICROSCOPE
AIR-VOID ANALYSIS IN CONCRETE
Modified Point Count Method of ASTM C 457
Air voids are an important component of concrete that provide many benefits. Improved workability in plastic concrete, a reduction in bleeding rate, and improved freeze-thaw resistance in hardened concrete are some of its blessings. Lack of adequate entrained air can cause scaling, which can be aggravated by the application of deicing salts. Too much air, on the other hand, reduces the compressive strength of concrete. Every 1% increase of air, at a given workability, can reduce the compressive strength by 3 to 5%. Clustering of air voids along aggregate-paste interfaces also reduces the compressive strength.
An unfortunate curse of entrained air is delamination. Entrained air in a machine-troweled slab increases the potential for delamination. Due to the importance of air voids, ASTM C 457 provides two standardized methods of determination of air-void system in hardened concrete—the Linear Traverse Method and The Modified Point Count Method.
CMC’s air-void laboratory has two set-ups of Velmex Unislide-VXM systems of semi-automatic, computer-controlled, air-void measurements by following the modified point-count method of ASTM C 457 and simultaneous data collection capabilities that not only helpful to provide the overall air-void system of hardened concrete but also the profiles of air-void parameters through depth. Air profiles are helpful to determine any finishing-induced loss of air at the surface.
Four parameters that determine the quality of an air-void system for freeze-thaw resistance of concrete are:
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Total amount or volume of air, including separate amounts of entrained and entrapped air
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Closeness of the voids as measured by void-spacing factor,
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Fineness of air voids measured by specific surface, and
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Distribution of air throughout the concrete from the wearing surface to the interior.
All these parameters are determined in air-void analysis of a lapped cross section of concrete core through the depth from the wearing surface by the linear traverse or modified point count method in ASTM C 457.
AIR-VOID ANALYSIS IN CONCRETE
Black and White Contrast Enhancement by Flatbed Scanner Method (Peterson et al. 2016)
FLUORESCENT-LIGHT MICROSCOPY
NIGHTSEA Fluorescent Viewing Systems On A Stereomicroscope
The NIGHTSEA stereo-microscope fluorescence adapter from Electron Microscopy Sciences adapts just about any stereomicroscope for fluorescence microscopy of fluorescent dye-mixed epoxy-impregnated thin section or polished section of concrete, mortar, or other materials with no modification to the microscope itself. The modular design helps to easily switch between normal strereo-microscopical observations followed by fluorescent microscopy to highlight voids, porous areas, and cracks in the samples. A large area of sample can be photographed to show the features of interest that are highlighted by fluorescent microscopy.
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FLUORESCENT-LIGHT MICROSCOPY
Reflected (Epi)-fluorescence & Transmitted Fluorescence Microscopy
Fluorescence-light Microscopy of Concrete
Fluorescence-light Microscopy of Concrete
Fluorescence-light Microscopy of Concrete
Fluorescence-light Microscopy of Concrete
SIR HENRY CLIFTON SORBY
The Founder of Petrography
Copyright materials, not to be downloaded
Published by American Society for Testing and Materials, 1966
Published by ASTM International, 1994
Published by Portland Cement Association, 1959
Published by Scientific American, 1964
Published by National Bureau of Standards, 1960
Published in Reviews in Engineering Geology by Geological Society of America, 1962
Stanton Walker Lecture Series on the Materials Sciences, 1964
Published by ASTM International, 1994
Published by ASTM International, 1966
Published by ASTM International, 1974
Published by U.S. Army Corps of Engineers, 1965
Published by ASTM International, 1950
Published by ASTM International, 1953
Published in ASTM International, 1965
Published by Association for Preservation Technology, 1987
Published in Quarterly Journal of Engineering Geology by The Geological Society of London, 1991
Published by International Cement Microscopy Association, 1983
Published by ASTM International, 1994
Published by Danish Technological Institute, 1985
Published by ASTM International, 1994
Published by Technical University of Denmark, 1967
Published by Federal Highway Administration, U.S. Department of Transportation, 2004
Published by American Ceramic Society, 1998
Published in 8th ICCC, 1986
Published in 8th ICCC, 1986
Euroseminar on microscopy applied to building materials, 1997
Published by Heyden, 1981
Published by Applied Science Publishers, 1983
SOME PIONEERING PAPERS ON
CONCRETE PETROGRAPHY
Copyright materials, not to be downloaded
GENERAL PUBLICATIONS OF CMC ON APPLICATIONS OF PETROGRAPHY IN CONSTRUCTION MATERIALS
You can download these publications.
For more articles, please see our publication page
January 27, 2006
International Seminar on Non-Destructive Testing Organized by the India Chapter of American Concrete Institute, and American Concrete Institute (USA)
June, 2006
Published in "Concrete Solutions - Proceedings of the Second International Conference" St. Malo, France, Edited by Michael G. Grantham, Rauol Jaubertie, and Christophe Lanos, BRE Press
April, 2017
Powerpoint presentation given in the 39th Conference of International Cement Microscopy Association in Toronto, Canada
1997
Originally accepted for publication by the American Concrete Institute after their peer-review process for their Publications For Practitioners Series, this two-part article written by Dipayan Jana and late Shondeep L Sarkar gives a general overview of various applications of microscopy in troubleshooting concrete problems.
SOME EXCELLENT ARTICLES ON OPTICAL MICROSCOPY
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