Concrete & Cement-Based Materials
Concrete is the most prevalent building material used in our society today. Its universal use in a variety of civil engineering applications is due to its widespread availability, cost-effectiveness, structural characteristics, and ability to be molded into limitless geometries. Yet, variables in design, production, material compatibility, construction, and exposure can compromise concrete’s structural integrity, durability, and aesthetics.
Exponent provides a wide range of consulting services to help owners, government agencies and municipalities, insurance carriers, general contractors, product manufacturers and suppliers, and construction attorneys solve complex issues involving the use of concrete and cement-based materials.
Exponent takes advantage of combined resources in many scientific and engineering disciplines including material science, civil engineering, metallurgy, and geology. Coupled with state-of-the-art laboratory testing capabilities and over forty years of experience investigating failures, Exponent is uniquely qualified to evaluate the cause(s) of and appropriate solutions to poorly performing concrete construction.
Exponent’s services in the area of concrete and cement-based materials include:
- Failure Investigation
- Root cause analysis
- Site inspection and field evaluation
- Material deterioration examination
- Construction, design and material defect evaluation
- Non-destructive testing and petrographic examination
- Concrete mix design analysis
- Strength and material properties testing
- Finishing and appearance assessment
- Litigation Support and Expert Witness Testimony
- Research and Development Support
- Product performance evaluation
- Standard and custom laboratory testing
- Construction and pre-construction materials consulting
- Green/sustainable concrete research
- Condition Assessment
- Structural integrity evaluation
- Failure risk assessment
- Service life prediction
- Repair design and recommendations
- Historic preservation
- Building code conformance
Expertise Related to Concrete and Cement-Based Materials
Exponent has experience investigating a variety of problems associated with concrete and cement-based materials including the following:
Cracking: Due to its brittle nature and relatively low tensile strength, concrete is susceptible to cracking. While some cracking is expected in virtually all concrete construction, cracking may have detrimental effects on concrete performance and longevity of a structure. Concrete cracking is often caused by one or more of the following: excessive loading, shrinkage, thermal contraction, corrosion of embedded reinforcement, chemical attack, freeze-thaw action, insufficient consolidation, inadequate jointing, improper support, and other factors.
Surface Problems: Scaling, delamination and excessive wear affect slab performance and are often the result of improper construction practices and/or inadequate concrete mix design for the service environment. If not finished properly, flatness, levelness, and surface quality may not meet the needs of other trades or the end user.
Reinforcement Corrosion: The expansive nature of reinforcement corrosion leads to cracking and spalling of concrete. Factors contributing to corrosion include insufficient protective cover, poor quality concrete, chloride ion penetration, and concrete carbonation.
Frost Damage: Environmental exposure to harsh weather conditions, such as cyclical freezing and thawing (F-T), may result in severe deterioration if concrete is not adequately designed, mixed and constructed. The problem can be exacerbated by the use of deicing salts.
Chemical Degradation: While concrete is non-reactive in most environments, degradation can occur due to acid attack, alkali-silica reaction (ASR), alkali-carbonate reaction (ACR), sulfate attack and exposure to corrosive chemicals.
Surface Coating Failure: Excessive moisture vapor emission, inadequate surface preparation and material incompatibility can cause coating failures. Failure is typically manifested in the form of blistering, debonding, discoloration and peeling of coatings.
Stone Veneer/Tile Distress: Debonding of adhered veneer from building façades may be the result of inadequate installation practices or material defects and can create a life safety hazard. Other common problems with performance of tile include discoloration and cracking.
Stucco Distress: Excessive cracking, warping and delamination of portland cement plaster (stucco) can be caused by structural movement, inadequate application, improper curing or inadequate proportioning of the plaster mix.
Fiber-Cement Materials Degradation: Fiber-cement products used as exterior cladding occasionally experience problems in the form of warping, cracking, and deterioration. Causes can be inadequate installation, thermal and moisture effects, or manufacturing errors.
Asbestos-Cement Pipe Deterioration: Asbestos-cement (AC) pipe which was extensively used in water distribution systems in the U.S. is nearing the end of useful service life. Gradual degradation due to leaching of calcium from cement matrix occurs in the pipe wall due to service environment.
Slab Moisture Vapor Emission: Excessive transmission of water vapor through concrete slabs can result in problems such as failures of moisture sensitive floor coverings, biological growth and construction delays. Slab moisture vapor emission rate is affected by slab thickness, slab age, slab exposure conditions, concrete mix design, sub-surface conditions and other factors.