According to a paper by Josef Ondrasina, published by the Geological Society of London, the freeze/thaw cycle damages marble and other stone "by progressive microfracturing or the loss of cohesion along grain boundaries due to the crystallization pressure of ice growth."
The CTS lab is equipped with both walk-in freezers and an industrial oven for thermal testing - artificially accelerating the weathering process by exposing the materials to extreme cold and heat.
Weak points in sandstone occur because of its layered composition, Gary said. "It can create a weak zone so they have to be very careful how it's cut out of the quarry and also how it's prepared and installed."
Gary also engages in forensic testing of materials for use by parties involved in lawsuits.
"I did some testing for a project that was for litigation purposes. It happened to be on some sandstone. There were panels falling off a building because of the way the stone had been cut and the way it was installed on the building."
Forensic investigations involve a careful recreation of the conditions of the material failure. "We build mock-ups to more or less recreate entire systems to see what part of the system is failing or to determine why it is failing," Gary said.
CTS has been doing flexural testing for stone being used in the brand new George W. Bush Presidential Center in Dallas.
The tests, performed according to ASTM standards, provide data about how stone panels will behave when they are subjected to loads either perpendicular or parallel to their bedding planes.
The George W. Bush Presidential Center is being constructed on a 23-acre lot on the campus of Southern Methodist University in Dallas, Texas. It will include a presidential library, archives and museum.
Flexural strength tests are important when stone panels are being installed inside or outside buildings. Usually, the panels are mounted independently and are only subjected to the weight of the panel itself, but design preferences can sometimes force builders to place the panels in weaker configurations.
"(The strength of the panels) may be jeopardized when an architect or building owner has a certain appearance they desire especially when the veining in the stone is very visible," Gary said.
To ensure good testing results, Gary uses several benchmarks: 1) Obtaining an estimated load at which the product should fail; 2) Making sure the product failed as anticipated and not as a result of the test methodology or fixtures; and 3) Having a sufficient quantity of samples for further testing if questionable results are produced.
It's not just stone that CTS tests. From theater and stadium seating to trailer hitches, Gary said his company is willing to test just about any component. The lab is engaged in testing landing gear components for the U.S. military's F-35 Joint Strike Fighter, which is currently under development.
According to news reports, the Defense Department plans to field the aircraft in 2016. Variations being developed include an Air Force version, an aircraft carrier-suitable version for the Navy and a vertical landing version for the Marine Corps.
Whether helping firms determine the best material to use in projects before the first panel is laid or looking into failures after the fact, CTS strives to aid architects and builders in creating the best designs possible.
For more information, please visit www.ctsciences.com or contact Jack Gary at 214-703-8911.
Above: C880 testing flexural strength on Permian Sea Coral. Inset: Freeze/thaw test Noir de Alpes Marble.
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