ASTM C90 Standard Specification for Load-Bearing Concrete Masonry Units

Get Certified ASTM C90 for Reliable Concrete Masonry Unit Quality 

Contractors and manufacturers rely on certified ASTM C90 testing because concrete masonry units are expected to perform under service conditions without failure, in terms of load-bearing, moisture resistance, and shrinkage resistance. The compressive strength and absorption characteristics are directly related to the durability and load-bearing ability of masonry walls. Certified testing confirms that a batch of concrete masonry units meets its specified weight classification and physical requirements before use in construction. 

The scope of ASTM C90 includes:

• Material type: Hollow and solid concrete masonry units using hydraulic cement, water, and mineral aggregates. 
• Purpose: To establish physical specifications for load-bearing and nonload-bearing concrete masonry units. 
• Properties measured: Dimensions, minimum net area compressive strength, maximum water absorption, and maximum linear drying shrinkage. 
• Method: ASTM C140 sampling and testing; linear drying shrinkage ASTM C426. 
• Result: Acceptance or rejection in accordance with the unit requirements for the assigned weight classification. 
• Test Limitations: Requirements apply to units produced on equipment with low- or zero-slump concrete; color or texture features are not included in the requirements. 
• Use conditions: Units are available as Normal Weight, Medium Weight, and Lightweight depending on concrete density. 
• Applications: For load-bearing and non-load-bearing walls, foundations, and other masonry construction. 

What are the Uses of ASTM C90 Testing?

ASTM C90 testing provides manufacturers with a standard method to verify the physical properties of a concrete masonry unit and allows engineers to verify the suitability of concrete masonry units for structural and nonstructural applications. This standard-

• Checks minimum compressive strength of the net area for load-bearing uses.
• Verifies maximum water absorption for Normal Weight, Medium Weight, and Lightweight.
• Helps confirm dimensional tolerances for overall unit dimensions and molded features.
• Helps calculate the maximum linear drying shrinkage to reduce the risk of cracking.
• Collaborates with quality control in producing hollow and solid concrete masonry units.
• Helps architects and engineers in the selection of units for load-bearing or non-load-bearing construction. 

Which materials can be tested under ASTM C90?

ASTM C90 tests hollow or solid concrete masonry units made from hydraulic cement, water, and mineral aggregates, from lightweight aggregates, normal weight aggregates, or a combination of both. The specification includes three weight classifications based on the type of aggregate and the resulting unit density. Manufacturers use a representative sample of the production batch to test for dimensional, strength, absorption, and shrinkage requirements for the assigned classification. 

Why is ASTM C90 Important? 

ASTM C90 testing allows manufacturers to verify that units meet these established requirements, which helps ensure durable, code-compliant masonry construction and reduces the risk of premature deterioration in service. The concrete masonry units offer dependable structural strength in load-bearing walls, as well as acceptable moisture absorption and shrinkage cracking over time. ASTM C90 requirements have been developed and researched over many years and are specifically applicable to units produced on equipment that uses low or zero slump concrete. 

ASTM C90 Testing Process and Data Collection

This process starts with an analyst taking representative samples of Concrete Masonry Units (CMUs) from a production lot following the ASTM C140 procedure. The technician then measures the units’ dimensions and compares them with the specified tolerances. The operator records the net-area compressive strength and water absorption for each unit during the strength and absorption test. The results are then all compared with the requirements for the assigned weight classification of that unit at the conclusion of the analyses. 

Common Challenges and Troubleshooting

Accurate ASTM C90 results require proper sampling per ASTM C140, dimensional accuracy, and calibrated compression testing equipment. Different amounts of moisture in the aggregate, uneven curing, and improper handling of specimens cause errors in compressive strength and absorption readings. Technicians minimize these problems by adhering to the procedures of ASTM C140 for sampling and conditioning and verifying equipment calibration prior to testing. Manufacturers also get consistent results from testing of units produced from the same lot and tested in the same conditions. 

• The laboratory uses ASTM C140 testing to report net area compressive strength for individual units and as the sample average.
• The technician notes water absorption and checks it against the maximum allowable water absorption for the units’ weight category.
• The analyst checks the overall dimensions and the tolerances of the molded features and compares them to the specifications.
• The engineer uses this information to interpret the results, considering weight classification, aggregate type, and manufacturing process.
• The manufacturer uses the measured properties to confirm acceptance and quality control for the concrete masonry unit production run. 

Link to ASTM C90