Forensic Evaluation – Evaluation of Cracked Concrete Driveway

Problem:

A one-year old concrete driveway at a home in Woodlands, Texas has sustained severe and extensive cracking. The goal was to identify the potential cause(s) of the cracking.

Evaluation Method/Process:

Cores were taken and evaluated by:

  • Petrographic Analysis
  • Compression Testing

Findings:

Petrographic analysis revealed the concrete to be well proportioned with the appropriate cement content and water-to-cement ratio. The paste matrix was also found to be consistently dense.

The defects noted, extensive cracking, was found to be due to sub-par aggregates used, which had inherent cracks. During the mixing of the concrete, these inherently cracked aggregates chip off and trap voids within the concrete. These voids tend to connect and form cracks when load is applied to the driveway.

The samples all met the compressive strength requirement. Concrete structures can meet the design strength and still have defects.

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Front view of the residence.

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Samples taken from the driveway.

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Typical cracks seen on the driveway.

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Sample taken on crack shows rusted rebar. Sample taken near flower-bed where frequent watering occurs.

Photos of Petrographic Analysis

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Shows inherently cracked aggregate.

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Shows void created by chipped off aggregate.