MACTEC San Diego is pleased to announce they have been awarded a multi-year
on-call petrographic analysis services contract from The State of California.
The work is expected to include petrographic analysis and laboratory testing of
concrete, aggregates, rock and concrete related products such as stucco and
terrazzo. Pete Campbell, Manager of Engineering Services in San Diego and David
Wilson, Principal Engineer are the main contacts for this project.
MACTEC’s petrographic services have aided in the evaluation of structural
failures, and provided information to evaluate whether material failure was a
cause or contributor to problems discovered.
MACTEC’s petrographic services have been used to assess material quality,
evaluate the cause of failure or distress, predict future performance, and to
evaluate whether the material meets specifications.
Information obtained from concrete petrography includes:
- Estimated cement content and water cement ratio, fly-ash presence,
- Estimated air content and evaluation of the air void system,
- Quality and mineralogy of the aggregates and an evaluation of the presence or
potential for adverse reaction in the concrete such as alkali silica reaction
and delayed ettringite formation,
- Evaluation of the cause of cracking,
- Assessment of fire damage,
- Evaluation of finishing and curing practices, and
- Evaluation of the depth of carbonation and degree of hydration.
MACTEC provides full petrographic services for construction materials, including
concrete, masonry, aggregates, stucco, Terrazzo, mortar, grout, and clay
products.
Traditional petrographic evaluations are visual and microscopic examinations of
concrete materials by a qualified petrographer. Specimens used in the
petrographic examination are fracture surfaces of the material, plane polished
lapped sections, or thin sections ground to thickness of 30 microns.
Examinations are made using a wide field stereomicroscope at magnifications from
10X to 60X, or a polarized light microscope at magnifications up to 400X. When
applicable, phenolphthalein staining will be used to determine the extent of
carbonation, and uranyl acetate staining to indicate the presence of
alkali-aggregate reaction products.
Shrinkage Crack
Crack through Aggregate in Polyester Concrete
Concrete Samples
(2x)
(10x)
(25x)
(40x) using cross polarized light
(40x) using polarized light
(400x) using cross polaried light