AASHTO T358
Full Name
AASHTO T358 – Standard Method of Test for Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion Penetration
Scope
AASHTO T358 is a standard test method used to determine the surface resistivity of concrete, which serves as a rapid indicator of its ability to resist chloride ion penetration. Chloride ions, often from deicing salts or marine environments, can initiate corrosion of steel reinforcement within concrete, leading to structural damage and reduced service life. This test offers a non-destructive way to assess concrete’s vulnerability to such deterioration.
Key aspects of AASHTO T358:
- Principle: the test measures the electrical resistance of a concrete surface when saturated with a low-frequency alternating current. Higher resistivity indicates greater resistance to chloride ion penetration, while lower resistivity suggests increased susceptibility to chloride ingress and potential corrosion.
- Apparatus: the test requires a surface resistivity meter equipped with a Wenner probe array, which consists of four equally spaced electrodes. The outer electrodes apply a current, while the inner electrodes measure the resulting potential difference.
- Procedure: after preconditioning the concrete surface, the Wenner probe is placed in contact with it. A current is passed between the outer electrodes, and the potential difference between the inner electrodes is measured. This data is used to calculate the surface resistivity.
- Significance: surface resistivity testing provides a rapid and non-destructive method for assessing concrete’s resistance to chloride ion penetration. This information is crucial for quality control in concrete production, evaluation of existing structures, and decision-making regarding maintenance and repair strategies.
Applications of AASHTO T358:
- Quality control: concrete producers can use this test to evaluate the effectiveness of mix designs and admixtures in reducing chloride ion penetration.
- Condition assessment: engineers can employ the test to assess the durability of existing concrete structures and identify areas vulnerable to corrosion.
- Maintenance planning: surface resistivity data can inform maintenance and repair decisions, such as the application of protective coatings or cathodic protection systems.
- Research and development: the test is valuable for research on the relationship between concrete properties, resistivity, and long-term durability.
AASHTO T358 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the AASHTO T358 standard.
Our laboratory offers AASHTO T358 testing services, utilizing calibrated equipment and adhering to standardized procedures to ensure accurate and reliable results. By assessing the surface resistivity of your concrete, we can help you make informed decisions to protect and extend the life of your structures.
Contact us for more information.
Resources
Keywords
surface resistivity; chloride ion penetration; concrete; Wenner probe; electrical resistance; corrosion; durability; deicing salts; marine environment