ASTM C129 Standard Specification for Nonload-Bearing Concrete Masonry Units

Developed by the American Society for Testing and Materials (ASTM), ASTM C129 Standard Specification for Non-Load-Bearing Concrete Masonry Units covers both hollow and solid non-load-bearing concrete masonry units constructed from Portland cement, water, and mineral aggregates, with or without the addition of other materials. These units are designed for use in non-load-bearing partitions, but under certain conditions they may be suitable for use in non-load-bearing exterior walls above ground level that are effectively protected from the weather.

Concrete wall units manufactured under this specification must comply with the specified density classifications and compressive strength requirements.

Non-load-bearing reinforced concrete wall units manufactured to this specification must conform to one of the three density classes specified in the table entitled “Density classification requirements”:

• Lightweight: less than 1680 kg/m3
• Medium weight: 1680 to 2000 kg/m3
• Normal weight: more than 2000 kg/m3

Cementitious materials must meet these ASTM specifications:

• Portland cement (ASTM C150 standard)
• Blended hydraulic cements (ASTM C595 standard)
• Hydraulic cement (ASTM C1157 standard)
• Slaked lime, Type S (ASTM C207 standard)
• Ground granulated blast furnace slag (ASTM C989 standard)
• Pozzolans (ASTM C618) standard

The aggregate must meet the following ASTM specifications, but grading requirements do not necessarily apply:

• Normal weight aggregate (ASTM C33)
• Lightweight aggregate (ASTM C331)

Other ingredients, such as air entraining agents, coloring pigments, integral water repellents, finely ground silica, and other ingredients, must be predetermined as suitable for use in concrete masonry and must comply with applicable ASTM standards or be shown by testing or experience to be non-detrimental to the durability of concrete masonry units or any material commonly used in masonry.

Regarding physical requirements, upon delivery to the buyer, the units must meet the strength requirements specified in the table titled "Strength Requirements." A buyer is a public institution or authority, association, corporation, partnership, or individual who has entered into a contract or agreement to purchase or install concrete masonry units, or both. Delivery to the buyer is FOB ex-works, when the buyer or the buyer's agent transports the concrete masonry units, or FOB ex-site, when the manufacturer or the manufacturer's agent transports the concrete masonry units.

At the time of delivery to the purchaser, the total linear drying shrinkage of the units shall not exceed 0,065 percent. The net cross-sectional area of ​​the solid units in each plane parallel to the bearing surface shall not be less than 75 percent of the gross cross-sectional area measured in the same plane.

The minimum surface shell thickness must be no less than 13 mm. No overall dimension (width, height, and length) must differ from the specified standard dimensions by more than 3,2 mm. The standard unit dimensions are those specified by the manufacturer. The nominal dimensions of modular-sized units are equal to the standard dimensions plus the thickness of a mortar joint. The nominal dimensions of non-modular-sized units generally exceed the standard dimensions by 3,2 to 6,4 mm.

All units must be sound in finish and appearance and free from cracks or other defects which would prevent proper installation of the units or which would significantly impair the strength or permanence of the structure.

Materials used in non-load-bearing concrete wall units must meet specific ASTM standards to ensure quality and consistency:

• Cement: Hydraulic cement is used, including Portland cement or Portland limestone cement (according to ASTM C595 standard).
• Aggregates: Normal-weight aggregates must meet ASTM C33, and lightweight aggregates must meet ASTM C331. Grading requirements may be adjusted to meet producer needs.
• Other ingredients: Additives such as air-entraining agents, pigments, or water repellents must be proven suitable for concrete masonry and comply with relevant ASTM standards.

The ASTM C129 standard specifies the following physical properties to ensure that units meet performance expectations:

• Dimensions and tolerances: Units must conform to the specified dimensions with specified tolerances to ensure uniformity.
• Compressive strength: This standard specifies minimum compressive strength requirements, which are typically tested at 28 days to verify durability. For example, studies of hemp-reinforced blocks have shown that most mixtures, except those with high hemp content, meet the compressive strength requirements of ASTM C129.
• Density classifications: Units are classified as light, medium, or normal weight based on density, with lightweight units (e.g., perlite or cinder blocks) offering lower thermal conductivity.
• Linear drying shrinkage: The standard limits shrinkage to ensure dimensional stability over time.

Special features such as surface texture, colour or fire resistance are not mandatory but may be specified by the buyer after consultation with suppliers.

The ASTM C129 standard outlines the following sampling and testing procedures to verify compliance:

• Sampling: Units are randomly selected to represent the quality of the lot.
• Testing: Testing focuses on compressive strength, absorption, and dimensional accuracy. For example, studies on crumb rubber blocks showed a 56 percent strength reduction that failed ASTM C129, while control and high-density polyethylene-reinforced blocks performed well.
• Acceptance criteria: Units are accepted or rejected based on test results that meet specified requirements.

Non-load-bearing concrete wall units, according to ASTM C129, are primarily used for interior partitions due to their non-structural nature. They can also be used in non-load-bearing exterior walls above ground level if protected from moisture by cladding or sheathing. Lightweight versions (e.g., perlite or cinder blocks) offer improved thermal resistance, reducing energy costs by up to 150 percent compared to commercial blocks, as studies have shown.

As a result, ASTM C129 is a vital standard for ensuring the quality and performance of non-load-bearing concrete wall units. By specifying materials, physical properties, and testing procedures, it provides a reliable framework for manufacturers and constructors. Its application in non-load-bearing partitions and exterior walls, along with its continuous updating to reflect modern materials, has become a cornerstone of concrete wall construction.

Our organization, which has been serving for many years and meticulously following global developments in science and technology, conducts testing, measurement, and analysis in a wide range of areas for businesses in every sector with a skilled team and extensive infrastructure. In this context, we also provide testing services in accordance with ASTM C129 Standard Specification for Non-Load-Bearing Concrete Masonry Units.