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 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?”