Currently, ASTM C1670 limits shrinkage, as tested in accordance with ASTM C426, with a maximum shrinkage of 0.065% for specimens tested. The current limit was copied from the shrinkage requirement for dry-cast units. This shrinkage limit, along with industry control joint spacing limitations, reduces the potential for concrete masonry wall assemblies to develop shrinkage cracking. As adhered manufactured stone masonry veneer is a wet-cast product, imposing the same requirement for a dry-cast product does not seem rational. Further, there are not prescriptive recommendations for control joint spacing in adhered manufactured stone masonry veneer assemblies, since shrinkage cracking has not been an observed issue in such construction. Referencing a white paper titled Are Control Joints Needed with Adhered Concrete Masonry Vener (Nordmeyer 2011), the inherent nature of the adhered manufactured stone veneer assembly, which is comprised of built-in control joint by way of grouted joints between units, mitigates stresses induced by movement by contraction of expansion. Any cracking that may occur is accommodated across several grout joints throughout a wall assembly, equally distributing any separation. Therefore, prescriptive limitations on control joint spacing, along with a complementary drying shrinkage limitation, are not necessary for such assemblies. The inclusion of control joints on adhered veneer assemblies could potentially be detrimental to overall water resistance, as the presence of control joints could increase the number of tears and holes in the water resistive barrier. This ballot proposes to remove the requirement for linear drying shrinkage for adhered manufactured stone masonry veneer units.
Keywordsadhered; cementitious; concrete; manufactured; manufactured stone; masonry; veneer;