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2014FallShotcreteEMag

Shotcrete FAQs to insulate the outward face of the cavity enough to prevent morning after the shotcrete has been applied. However, our excessive condensation and moisture buildup. This would shotcrete company told us to keep the shell damp for a minimum certainly solve the sound problem (depending on the mass of 7 days. Could you weigh in on this? sprayed). Are there any suggestions or references you might be able direct me to? Answer: The ICC Building Code requires a 7-day wet cure, which is good practice for concrete or shotcrete. The Aquron Answer: A properly designed shotcrete composite wall system Technical Data Sheet mentions prewetting the surface prior to would certainly create a quiet atmosphere in the interior of the application, but we do not see the direction on the timing. You house. There are 3-D shotcrete wall systems on the market may want to question the product representative regarding how which use shotcrete on both the interior and exterior surfaces to accomplish the ICC curing requirements and also get the with a foam material in the center for insulation and vapor best results from their product. barrier. Attempting to do something like this to an existing structure would require a lot of analysis. Shotcrete is a method Question: I am considering using shotcrete for lining stormwater of placing concrete and adding shotcrete to an existing wall conveyance ditches at a project site, and am trying to find any would significantly increase the weight of the wall and could possible information on the potential for shotcrete (or other overload the footings or impact other parts of the system. A cement products for that matter) to leach selenium. Please structural engineer well-versed in residential construction advise if you have any information regarding this topic. should be consulted before attempting such a modification. Answer: Shotcrete is a method of placing concrete. Thus, Question: We are in the process of renovating a commercial testing for selenium appropriate for concrete is suitable for pool with a gutter system. The plaster surface has been removed shotcrete. The Portland Cement Association (PCA) has published along with some of the concrete. The wall of the gutter on the a paper on testing of cement for various constituent components, water side is tiled and is crumbling away. Our plan is to shotcrete including selenium, to meet NSF 61 requirements. Their testing the walls and gutter. showed “Values for arsenic, cadmium, selenium, and silver When we shoot the walls back we will be adding 1 to 2 in. were all below detection limits.” The paper can be found at (25 to 51 mm) of shotcrete at a maximum. Is this too thin for PCA’s website: www.cement.org/docs/default-source/ shotcrete? Also, the gutter edge will be 2 in. (51 mm) thick and fc-library/sp117.pdf. 4 in. (102 mm) in height without any reinforcing bar—will this have much strength? Question: How soon after a surface is shotcreted can it be submerged with stream water? What if the water has no velocity? Answer: Shotcrete can be placed as thin as 1 to 2 in. (25 to 51 mm), but will do little more than to provide a new surface to apply Answer: Shotcrete is a means of placing concrete and the same the plaster. To do a proper job you need to remove all loose precautions should be taken. Once the shotcrete had taken final and deteriorated existing shotcrete and should likely add in a set, exposing it to water and submerging it in water should layer of reinforcement or use structural fibers (either steel or enhance its curing. If it is a pool or other deep structure, you synthetic) in the shotcrete mixture. The surface preparation should ensure that the shotcrete or concrete is strong enough to should be done to the standards outlined by the International withstand any hydrostatic loading due to the filling of the structure. Concrete Repair Institute (ICRI). Question: I have a project in Fort Worth, TX, where we will be placing shotcrete on some interior walls that will have steel embeds for other structural supports. Do you have an article or literature regarding good practices of shotcrete placement around steel embeds? Answer: Shooting around embeds can be very challenging. The most important factor is to have the work done by a shotcrete Contractor Qualifications Nationally subcontractor who has done this successfully in the past and has ACI Certified Nozzlemen who are also experienced in this ACI Shotcrete Nozzleman Certification type of work. It has been done successfully on many projects in Locally through California-based ACI Chapters the past, but we do not have a published procedure to do this work. Question: We are building a pool using shotcrete, and our pool EXAMINER design team has been asked to use the Aquron pool shell protector. www.shotcrete.us The info from Aquron says for best results, spray the CPSP the Shotcrete • Fall 2014 65


2014FallShotcreteEMag
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