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2015SummerShotcreteEMag

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: What is the standard materials delivery rate velocity between the rock substrate and shotcrete, depending on tem- for shotcrete applications? peratures and thickness of the shotcrete, it may freeze. As with all concrete, shotcrete material can be air-entrained to enhance Answer: Recent research into velocity of the material stream resistance to freezing-and-thawing exposure. You should consult shot from the nozzle is approximately 60 to 80 mph (97 to with an experienced engineer to determine whether the type of 129 km/h) in the middle of the stream. Outer portions of the rock, geometry of the sections, and anchoring of the shotcrete stream are slowed and show speeds of about 45 mph (72 km/h). (such as with soil nails or rock bolts), along with the bond of Here’s a link to the Technical Tip published in the Fall 2013 shotcrete to the rock, will provide the desired performance. Shotcrete magazine that provides more complete documen - tation of the research: www.shotcrete.org/media/Archive/ Question: I have a very small job to do that would normally 2013Fal_TechnicalTip.pdf. be handled by a gunite or sprayed-on application. I need to form the inside of a concrete box into a cylindrical shape. I Question: We are planning on placing shotcrete over rock face would like to get a few hints or suggestions on how I might and are concerned about water seeping out of the rock and forming accomplish the “gunite” solution using my hands/tools only. ice behind the shotcrete. Could you please offer some insight? Does this require a special mix of the mortar mixture? Answer: Shotcrete is a functionally impermeable material when Answer: Shotcrete is concrete placed at high velocity to properly designed and placed. Thus, if water accumulates achieve compaction. It is dependent on the projection of mate- OnLine All ASA members and subscribers now have access to the electronic version of Shotcrete magazine. A link to this e-magazine is sent as an item in the “What’s in the Mix” e-newsletter. To ensure that you receive access to all future issues of the electronic version of the magazine, send your e-mail information to info@shotcrete.org. 62 Shotcrete • Summer 2015


2015SummerShotcreteEMag
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