AASHTO T21
Full Name
AASHTO T21 – Standard Method of Test for Organic Impurities in Fine Aggregates for Concrete
Scope
AASHTO T21 is a standard test method used to assess the presence of potentially harmful organic impurities in fine aggregates intended for use in concrete. These impurities can originate from decomposed vegetable matter, humus, or other organic sources and can negatively impact the setting time, strength development, and overall performance of concrete.
Key aspects of AASHTO T21:
- Purpose: the primary objective of this test is to provide a quick and simple method to determine whether a fine aggregate sample contains a significant amount of organic impurities that may require further testing or treatment before it can be used in concrete.
- Procedure: the test involves adding a sodium hydroxide solution to the fine aggregate sample and visually comparing the color of the resulting solution to a standard color reference or a glass color standard. The darker the color of the solution, the greater the concentration of organic impurities.
- Interpretation: AASHTO T21 provides guidelines for interpreting the test results. If the color of the solution is lighter than the standard, the aggregate is typically considered acceptable for use in concrete without further testing. If the color is darker, it indicates the presence of a potentially harmful amount of organic impurities, and further testing (such as a mortar strength test) may be required to assess their impact on the concrete properties.
Significance of AASHTO T21:
- Quality control: by performing this test, aggregate producers and contractors can ensure that the fine aggregates used in their projects meet the quality standards for organic impurities, minimizing the risk of adverse effects on the concrete.
- Early detection: AASHTO T21 serves as a preliminary screening test to detect the potential presence of harmful organic impurities. Early detection allows for timely corrective actions, such as washing or treating the aggregate, to mitigate any negative impacts on the concrete.
- Cost-effectiveness: the test is relatively simple and inexpensive to perform, making it a valuable tool for routine quality control in aggregate production and concrete construction.
AASHTO T21 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the AASHTO T21 standard.
Our laboratory offers comprehensive aggregate testing services, including the assessment of organic impurities according to AASHTO T21. Our experienced technicians utilize standardized procedures and equipment to ensure accurate and reliable results, helping you ensure the quality of your aggregates and the long-term performance of your concrete structures.
Contact us for more information.
Resources
Keywords
organic impurities; fine aggregate; concrete; sodium hydroxide solution; color comparison; standard color; deleterious substances