Petrographic Examination of Hardened Concrete

Understanding What Is Happening Inside Concrete

Concrete distress is not always visible from the surface. Cracking, deterioration, discoloration, scaling, and other problems may originate from conditions within the concrete itself.

C3S, Inc. uses petrographic examination to investigate the internal characteristics of concrete and help determine the causes of distress and deterioration.

What Is Petrographic Examination?

Petrographic examination is the microscopic evaluation of concrete and its constituent materials. It allows an experienced examiner to study the aggregate, cement paste, air-void system, cracks, interfaces, and other features within hardened concrete.

The examination can provide information that may not be available through visual inspection or conventional strength testing alone.

What Can Be Evaluated?

A petrographic investigation may evaluate:

• Aggregate type and condition
• Cement paste characteristics
• Aggregate-paste interfaces
• Cracking and crack patterns
• Air-void characteristics
• Paste distribution
• Evidence of improper consolidation
• Internal voids and defects
• Delamination and deterioration
• Alkali-silica reaction (ASR)
• Sulfate-related deterioration
• Freeze-thaw-related distress
• Aggregate-related problems
• Material incompatibility
• Construction-related conditions

How Does It Help?

Petrographic examination can help answer important questions:

• Why is the concrete cracking?
• Is deterioration occurring internally?
• Are the aggregates contributing to the problem?
• Is there evidence of ASR or another chemical reaction?
• Are construction practices contributing to the distress?
• Does the observed condition indicate a material-related problem?

Technical Methodology

Concrete cores or other representative samples may be prepared for microscopic examination. Depending on the investigation, the examination may be supplemented by additional laboratory or micro-analytical techniques.

The results are interpreted in conjunction with field observations, project documentation, testing data, and the history of the structure.

Applicable Standard

ASTM C856 — Petrographic Examination of Hardened Concrete

ASTM C856 provides procedures and guidance for petrographic examination of hardened concrete.

Related C3S, Inc. Services

• Forensic Investigation & Micro-Analysis
• Concrete Failure Evaluation
• Materials Investigation
• Laboratory Testing