Cracking in New Concrete Structures Expert Article

Concrete cracking in new construction is one of the most common matters encountered in construction defect litigation. A crack can be an indication that something went wrong. What it does not tell you (without investigation) is what went wrong, when it went wrong, and who could be responsible for cracks.

This article provides an overview of the most common causes, the forensic methods used to investigate them, and some relevant questions.

Common Causes of Cracking in New Concrete Structures

Not every crack is a defect. Some cracking in concrete is expected and, when properly controlled, can be harmless to the overall performance of that member. Other cracks might be an indication of design errors, improper materials, or quality control of construction methods.

Understanding the severity of the cracks and consideration of the location of the cracks are key elements in helping to determine the cause and the responsible parties, and are crucial steps in a forensic crack investigation.

Concrete cracking across residential, commercial, and industrial construction typically falls into a handful of common categories:

• Plastic Shrinkage
• Drying Shrinkage
• Thermal Cracking
• Improper concrete placement/consolidation/finishing
• Inadequate or Misplaced Reinforcement
• Overloading During Construction

Concrete is strong in compression, but it is weak in tension. When tensile stresses develop in a concrete element and exceed its tensile strength, a crack may form if not properly reinforced. The role of reinforcing steel placed in concrete is to resist the tensile forces that the concrete is incapable of resisting. What causes those tensile stresses that result in cracking is where the forensic investigation begins.

Determining the Cause of Concrete Cracking

A forensic investigation of concrete cracking will use physical evidence to determine the timeline of the cracking and the conditions that caused it. A forensic investigation might include a systematic crack survey comprised of documentation of the cracks by location, length, orientation, width, and depth using crack comparator gauges and photographic documentation.

Where warranted, cores are extracted from the in-situ concrete member to measure actual rebar cover, to verify compressive strength of the concrete, and to examine the concrete microstructure for evidence of placement or curing issues.

A review of the construction records would include:

• Mix design and batch tickets
• Placement logs
• Concrete testing performed at its discharge point (slump and compressive strength of concrete cylinders)
• Temperature monitoring records
• Curing documentation/methods
• Inspection logs

The applicable standards for concrete are typically the ACI family of documents, along with the project specifications.

Concrete Crack Investigation Questions

• The very first question to ask when crack(s) are observed is: Is the cracking detrimental to the aesthetic or to the performance of the structure?
• The next question in every concrete crack investigation is the same: did the responsible party's actions or inactions fall below the applicable standard of care, and was that failure a cause of the cracking?
• When were the cracks first noticed? Cracks within hours of placement can indicate plastic shrinkage. Cracks within weeks and/or months suggest drying shrinkage or thermal effects. Cracks that develop over months may indicate settlement of the structure or progressive structural overloading.
• What does the documentation say? Are the batch tickets and mix design available? These documents reveal whether the concrete delivered matched what was specified; strength, water-cement ratio, admixtures, and aggregate source.
• What do the concrete inspection reports say? There should be independent verification (i.e., beyond the contractor) that the concrete reinforcement was placed correctly, that the specified concrete cover was achieved, that the fresh concrete met the project specifications and that curing requirements (if specified) were followed.
• Were control joints specified and/or installed? For concrete slabs, the contract documents depicting the joint layout should be compared against what was constructed in the field and the actual crack locations in the field.
• Has the cracking progressed since it was first observed? Static cracks and progressive cracks have different implications. If cracking is still widening or new cracks are forming, the underlying cause is still active which will require a change of both the investigation approach and the damages analysis.
• What is the structural significance? A vertically-oriented hairline surface crack in a concrete wall is a different case than a through-member crack in an elevated concrete slab. Cracks must be evaluated in the context of the structural system they are in.

By the time an issue reaches litigation, the question is not just whether the concrete cracked, but are the cracks detrimental to the structure, and which decisions (by which parties) caused the cracking in a way that failed to meet the applicable standard of care.

Crack patterns may change as cracks are filled, patched, or overlaid. Core samples capture the concrete's condition at the time of the dispute. Batch records and inspection logs can be lost. A forensic engineer can assist with interrogatories, requests for production and deposition questions to help preserve and establish the evidentiary record.

Concrete Cracking Expert Investigations

The general contractor, concrete subcontractor, reinforcing subcontractor, ready-mix supplier, and structural engineer might all contribute to cracking of concrete members. A well-structured forensic investigation identifies the specific failure that produced the cracking, traces that failure to the party responsible for preventing it, and provides the technical foundation for the damages analysis.

For more information, submit an inquiry or call us at 800.813.6736.

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David Beh, P.E., MSCE

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David Beh is an expert in structural engineering with nearly two decades of professional experience in the design of buildings and a variety of other structures. He has specialized knowledge in wind,… read more.