ASTM Tests Applicable for Cladding and Dimension Stones

ASTM tests applicable for cladding and dimension stones are to be discussed here. Stone that is used as cladding is usually part of a curtain wall assembly that does not bear the load of the building; instead, it is attached to the structure in one of two ways. In the hand set method, each individual stone is individually placed and attached to either the primary building structure or a secondary wall framing system. In a panelized installation, stone panels are preinstalled into a frame or attached to a precast concrete panel. The panels are then attached to the building’s primary structure or to a secondary framing system.

Anchorage Systems in Cladding

In either case, anchors are used to attach the stones or panels. Anchorage systems must withstand the many forces that impact natural stone cladding. There are a number of anchorage system types, but in general, the best anchors are the simplest and designed with the fewest components. Anchors also should be carefully designed to prevent galvanic corrosion, which can cause the anchors to fail years after they have been installed. Because anchorage systems are so critical, special ASTM tests have been developed to evaluate them.

ASTM C1354: Strength of Individual Stone Anchorages for Dimension Stones

This method is used to test a particular anchorage in a prepared stone specimen. This small-scale test is used to establish the ultimate capacity of a given anchor in a given stone, the point at which the anchor fails under load. It is recommended that any filler that is to be used must be omitted for the test, or prevented from bonding to either the stone or the anchor during the test. This ensures that the anchor is being tested on its own merits and is not being “helped” by the filler. There is no “pass/fail” criteria for this test.

STM C1242 Standard Guide for Selection, Design, and Installation of Dimension Stone

STM C1242 Standard Guide for Selection, Design, and Installation of Dimension Stone Attachment Systems can be used to select the safety factor and calculate the allowable capacity of the anchor, which should be significantly lower than the ultimate capacity, as determined by then anchorage test.

ASTM C1201 Standard Test Method for Structural Performance of Exterior Dimension Stone Cladding

There is a test that can be used to evaluate entire assemblies instead of individual anchorages. ASTM C1201 is Standard Test Method for Structural Performance of Exterior Dimension Stone Cladding Systems by Uniform Static Air Pressure requires a full-scale mockup of a stone panel. The actual stone to be installed, cut to the specified dimensions and with the correct finish, is used for the mockup.

Anchorages are the actual types recommended in the design. The anchorage hardware is attached to a rigid frame which simulates the building structure. The mockup is enclosed in an air chamber and subjected to a simulated wind load. This test provides a more accurate picture of how the assembly will behave in the field. However, because this test is quite expensive, it is not used extensively.

Other Considerations for Exterior Stone

One important consideration for exterior stone applications is how the stone will hold up to repeated cycles of freezing and thawing. In general, less dense stones with greater absorption rates may be more vulnerable to degradation. Although there is no specific ASTM test to evaluate a stone subjected to freeze-thaw cycles, the specifier does have options. Samples can be sent to an independent lab for an Accelerated Weathering test. There stones are placed in an environmental simulation chamber and subjected to any number of conditions, including temperature and humidity cycling. The stones are tested for flexural strength before and after their time in the chamber to evaluate the rate of degradation.

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Sources

continuingeducation.bnpmedia.com/courses/natural-stone-institute/the-importance-of-testing-when-specifying-natural-stone/4/