Standard Active Last Updated: Jul 20, 2018
ASTM C946-18

Standard Practice for Construction of Dry-Stacked, Surface-Bonded Walls


This practice covers material, workmanship, and construction procedures for applying surface bonded mortar to both sides of dry stacked concrete masonry units. Mortar shall be mixed and shall be selected in accordance with the proportion specification prescribed. Shims shall be corrosion-resistant metal or plastic with a required minimum compressive strength. Courses of concrete masonry units between the leveling courses shall be placed without mortar on the bed or head joints. Place units in running bond. Remove burrs and butt blocks tightly. Use shims, mortar, or surface bonding mortar to plum and level individual units when necessary. Use clean mixing equipment and water free of deleterious amounts of acid, alkali, and organic materials. Mix only full bag multiples of material to overcome any segregation of ingredients. Mixing time shall be kept to a minimum, as over mixing may cause damage to the fibers. Before applying surface bonding mortar, wet the wall uniformly with water to prevent excessive suction of water from the surface bonding mortar. Trowel- or spray-apply surface bonding mortar to both sides of dry-stacked concrete masonry units. When a second coat of surface bonding mortar is to be applied, the first coat shall have taken its initial set. Dampen the wall with a water mist after a specified time, but within a day of application of surface bonding mortar. The top of the walls shall be covered with a nonstaining, waterproof covering to prevent moisture from entering the wall until the top is permanently protected.


1.1 This practice covers material, workmanship, and construction procedures for applying surface bonded mortar to both sides of dry stacked concrete masonry units. It does not include grout, reinforcing, anchorage, or control joints since their use is essentially the same as conventional concrete masonry construction, unless specifically mentioned in this practice.

Note 1: Design and construction procedures for conventional concrete masonry construction are found in Building Code Requirements for Masonry Structures (TMS 402-16) and Specification for Masonry Structures (TMS 602-16).

1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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Book of Standards Volume: 04.05
Developed by Subcommittee: C12.06
Pages: 3
DOI: 10.1520/C0946-18
ICS Code: 91.060.10