Title page for ETD etd-4554162539751141

Type of Document

Dissertation

Author

Scott, Michael Leon

Author's Email Address

miscott@vt.edu

URN

etd-4554162539751141

Title

Determining the Air Void Parameters of Concrete Using Digital Image Analysis of Polarized Light Micrographs

Degree

Master of Science

Department

Engineering Science and Mechanics

Advisory Committee

Advisor Name	Title
Duke, John C. Jr.	Committee Member
Henneke, Edmund G. II	committee member
Weyers, Richard E.	committee member

Keywords

powers spacing factor
image analysis
Concrete
microscopy

Date of Defense

1997-04-22

Availability

unrestricted

Abstract

Abstract The ASTM C457 test has long been a standard

used to obtain the air void parameters of concrete

materials. These air void parameters provide valuable

information that has been linked to the performance of

concrete under conditions such as freezing and thawing

cycles. The standard test procedure involves linearly

traversing a cut and polished section of a concrete

specimen while a technician observes it under a

microscope. Chord lengths of material constituents that the

technician observes along the linear traverse are recorded

and later used to calculate air void parameters statistically.

This procedure is long and tedious, which makes it

susceptible to human error due to operator fatigue. This

study proposes and implements a new test method for

evaluating concrete air void parameters using an image

analysis method. A polishing procedure along with a

differential interference contrast microscope are used to

obtain high contrast images of material constituents, which

provide raw data for the image analysis method. Because

of the high contrast that can be obtained, cement paste, air

voids in the cement paste, and aggregate materials in the

concrete can be distinguished from one another based on

these images. An image analysis program has been written

for this study which linearly traverses these images and

records the chord lengths of material constituents in a

similar way to the standard ASTM C457 test. The chord

length data must be processed further, however, because

features in the images can be truncated by the edge of the

image. Correction calculations for this problem are

implemented in the image analysis algorithm. Two

specimens which have been previously tested using the

standard ASTM C457 method by the Virginia

Transportation Research Council, (VTRC), are used in this

study. The air void parameters obtained using the new test

are compared directly with the results obtained by VTRC

for the two specimens. Statistical comparisons indicate that

the results of the new test are indeed significant, showing

the potential it has for practical implementation. There are

drawbacks to the test including a long polishing procedure,

but this process can be automated. The new test appears

to have excellent potential for practical application, but it

should be emphasized that the test has only been

implemented using materials in two concrete specimens.

Further study on a variety of other concrete materials

would be required for implementation in a standard

procedure.

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