Our petrographer typically use: • Visual examination of the sample • Stereo microscopy to inspect surfaces and fracture features • Polarized light microscopy to examine thin sections of the material • High-resolution photography and photomicrographs • Sometimes supplemental testing such as chemical analysis or scanning electron microscopy (SEM)

A petrographic examination can help answer questions such as:

• Why are my compressive strength values less than the design?
• How do I know the provided concrete matches the mix design?
• Was too much air entrainment added to the concrete?
• Is it time to remove and replace the existing concrete slab?
• Why do I have so much efflorescence on my concrete?
• Did the material quality contribute to the building collapse?
• What is the condition of the concrete in the old building?
• What is the probable future performance of my concrete?
• Why is my slab surface color blotchy?
• How much surface preparation is required?
• Why are there so many cracks in my slab?
• Why did the surface of the concrete flake off?
• What materials were used in the historic mortar?
• Can this aggregate be used in concrete?
• Why is this concrete cracking?
• Is the aggregate causing deterioration?
• Was the concrete made according to the specified mix design?
• Is there evidence of poor workmanship or improper curing?
• Is this an alkali-silica reaction (ASR)?
• Has freeze-thaw damage occurred? • Is sulfate attack present?
• Are there signs of delayed ettringite formation (DEF)?
• Why did this pavement, bridge deck, or structure fail prematurely?
• What minerals are present in the aggregate?

 

ASTM C856: Used for hardened concrete investigations ASTM C856 is the standard practice for petrographic examination of hardened concrete.

ASTM C295: Used to evaluate aggregates before use or during failure investigations. ASTM C295 is the standard guide for petrographic examination of aggregates for concrete.

ASTM C1324: Used for mortar analysis. ASTM C1324 is the standard test method for examination and analysis of hardened masonry mortar.

Petrography is the microscopic analysis of rocks, minerals, and other materials used to determine their mineralogical composition, fabric, and physical characteristics. By preparing samples as thin sections and examining them under optical and analytical microscopes, petrographers can characterize constituent phases, assess material performance, and investigate the causes of degradation and failure.

Petrography is most valuable during:

• Failure investigations – determining why a structure deteriorated.
• Pre-construction material qualification – assessing aggregate suitability.
• Litigation and insurance claims – providing independent technical evidence.
• Condition assessments – evaluating existing structures.
• Quality assurance and troubleshooting – verifying materials and workmanship.

Used by engineers, consultants, contractors, DOTs, attorneys, and owners, petrography often provides the evidence needed to answer the most important question: “What happened, and why?”