In order to determine compressive strength of ungrouted masonry prisms, it is important to have the correct net area of the prisms. For ungrouted constructed prisms, such prisms have full mortar beds, and the net area of the prisms is the same as the net area of the units used for construction. The accurate way to determine the net area is by using the same procedures as for hollow masonry units. These procedures are detailed in ASTM C140 for concrete units and ASTM C67 for clay units. ASTM C1314, however, currently allows either those methods, or simply by measurement of the prism. The current language allowing Net Area for ungrouted prisms to be determined by measurement does not clarify the location and nature of the measurements required. The Average Net Area for hollow concrete masonry units is specifically defined in C140 as the Net Volume divided by the block height. This value cannot be obtained by dimensional measurement alone. The term in C67 is specifically defined as the net area of the fired clay in the section of minimum area perpendicular to the direction of the load. C1314 should ensure that the Net Area used for this test is accurate, repeatable, and consistent with these standards. This ballot proposes to modify the language for net area of ungrouted constructed prisms to make it clear that net area needs to be determined by testing additional units representative of those used in the prisms using the appropriate test method. Note that this change does not affect the considerations necessary for prisms removed from existing construction. The changes are limited to ungrouted constructed prisms.
Keywordscompressive strength of masonry (
Ballot Item Approved as C1314-2014 and Pending Publication