• Low-power Stereozoom microscope

  • Low to high-power reflected and transmitted-light Stereozoom microscope

  • Petrographic microscope having facilities for

    • Transmitted-polarized light (for plane and crossed-polarized light observations of a thin section),

    • Reflected-light (for examination of a polished thin or solid   section), and

    • Epi-fluorescent light (for examination of a fluorescent thin section);

  • Metallurgical microscope for examination of polished solid samples

  • Phase contrast microscope

  • USB microscope

  • Air-void analysis by a Stereozoom microscope attached to a stepper-motor controlled X-Y stage and air-void analysis software

CONCRETE UNDER MICROSCOPE

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:

 

  • Total amount or volume of air, including separate amounts of entrained and entrapped air

  • Closeness of the voids as measured by void-spacing factor, 

  • Fineness of air voids measured by specific surface, and 

  • 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. 

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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. 

FLUORESCENT-LIGHT MICROSCOPY

Reflected (Epi)-fluorescence & Transmitted Fluorescence Microscopy

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

SOME EXCELLENT ARTICLES ON OPTICAL MICROSCOPY

Copyright materials, not to be downloaded

SOME YOUTUBE VIDEOS ON OPTICAL MICROSCOPY

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Berkshire Center
4727 Route 30, Suite 104
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USA

Phone: 724-834-3551

Fax: 724-834-3556

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