Full-scale flexural strength testing for stone cladding design

Beginning with the Industrial Revolution and rapidly increasing following World War II, building cladding systems changed dramatically. Exterior wall construction that had previously consisted of thick mass masonry evolved into contemporary curtain wall systems. As curtain wall systems evolved, the economics of reducing the thickness of curtain wall components became more important. The use of thin stone veneers on buildings in the modern era was not associated with increased knowledge of stone material properties based on testing and research. Rather, the reduction in thickness is attributable to advancements in fabrication technology, economy in construction, and a rational approach to design of veneer systems. This paper will discuss the evolution of the use of stone in curtain wall systems and the associated ASTM standards for building stone. Early ASTM standards for building stone were limited to tests used to evaluate the compression strength of stone which was consistent for mass bearing walls of the early 20th century. As stone was increasingly used more as a veneer, standards for modulus of rupture (ASTM C 99) were introduced. As systems continued to evolve, flexural strength (ASTM C 880) was introduced to address material variability. The evolution of ASTM C 880 included increasing specimen width to further incorporate variability of the stone. Recently, the authors have introduced full panel testing in the design and evaluation process. This paper will present data and discuss the differences in test results for three case studies where both ASTM C 880 specimens and full panel flexural strength testing was performed. The focus of this section will be to discuss the implications of performing full-size panel testing in addition to ASTM C 880 standard specimen testing on design of stone cladding systems for tall building construction as a natural evolution of the design and evaluation process for thin stone cladding systems. Copyright © 2007 by ASTM International.