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2017SummerShotcreteEMag

| SHOTCRETE FAQs As a service to our readers, each issue of Shotcrete will include selected questions and provide answers by the American Shotcrete Association (ASA). Questions can be submitted to info@shotcrete.org. Selected FAQs can also be found on the ASA website, http://shotcrete.org/pages/products-services/technical-questions.htm. Question: We want to know if it’s possible to apply a 1 in. (25 mm) lift of shotcrete to a berm (2:1 slope). The berm will be treated with emulsion (oil and water) prior to the shotcrete. We are only looking for long-term erosion control. Will the emulsion be required or will it cause a bonding problem with the soil? Answer: Shotcrete is a placement method for concrete. If the berm is composed of granular materials, one wouldn’t expect the shotcrete to actually bond to the soil. Rather, placing a thin shotcrete layer would create a uniform, relatively impermeable layer of concrete to prevent water from penetrating through and washing out the soil underneath. The emulsion may help to stabilize the soil to help withstand the pressure of shotcreting directly against the berm, but many similar soil stabilization projects will shotcrete directly onto the natural soils. Also, when considering using the emulsion, be aware that some oils may contain ingredients (like sulfur) that can attack the concrete over time. You should consult with an engineer or concrete materials specialist to ascertain whether the specific oil you want to use will have a longterm effect on the shotcreted layer. Question: I have a contractor requiring cast 4 x 8 in. (100 x 200 mm) cylinders instead of test panels. Is there a written procedure for casting cylinders for shotcrete? Answer: Shotcrete compressive strength should be tested using cores from test panels. Shotcrete cannot be shot into closed cylinder forms and be representative of the in-place shotcrete. ASTM C1140-11 and C1604-05(2012) provides the panel configuration and compression testing requirements. However, if using the wet-mix process for shotcreting and one wants to verify the compressive strength, air content, or temperature of ready mixed concrete materials as delivered, rather than as shotcreted in place, samples can be taken from the truck before pumping. These cylinders would follow ASTM C31-15 for making and curing concrete test specimens. Question: We are looking for the application of shotcrete on tidal waters. We are located on Lower Puget Sound in Washington state and need examples where this has been used and is holding up under the moving tides. Answer: Shotcrete is a placement method for high-quality concrete. Here’s a link to an article of a rehabilitation of a concrete-supported lighthouse in the St. Lawrence Seaway (Pointe de la Prairie Lighthouse) that provides a lot of detail on an installation like yours, including saltwater exposure in a tidal zone. Additionally, this project also has regular freezing-and-thawing exposure (www.shotcrete.org/ media/Archive/2014Sum_Sustainability.pdf). Another project with tidal zone exposure involved repair of bridge pier pile caps on the East Coast of Florida. The article details the project parameters and testing conducted to verify the quality of the shotcrete placement (www. shotcrete.org/media/Archive/2012Win_White.pdf). Question: I am currently working on a construction project that involves a soil nail retaining wall along a major highway UPCOMING ISSUES OF shotcreteMAGAZINE Fall 2017 — ASA 20th Anniversary edition Winter 2018 — Contractors Spring 2018 — Outstanding Shotcrete Project Awards 68 Shotcrete | Summer 2017 www.shotcrete.org


2017SummerShotcreteEMag
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