Frequently, shotcrete contractors are required to shoot test panels at the beginning as well as throughout projects. Several tests are performed from these panels; however, compressive strength testing is the most common. This article will primarily address compressive strength testing. At some point, every contractor has missed a required break strength on a core extracted from one of their panels. Frequently, those bad results are not caused by bad material or poor workmanship. They are caused by poor test panel handling and improperly performed test standards. Often, the causes of those bad test results could have been easily avoided. Let’s discuss some of the more common test panel mistakes witnessed in the field
I live in a 10-story condo building built in the 1960s. The entire building is made of gunite. We use masonry drill bits for holes, but nothing seems to grip well. We have tried concrete screws, metal drywall anchors (which seem to work the best), and a plethora of other anchors and screws, but nothing seems to work. They all cause mushrooming and they either don’t grip or turn the wall to powder. What are the best tools to affix things to the walls?
Shotcrete is a placement method for concrete. Dry-mix shotcrete (the old tradename is gunite) using proper materials, equipment, and application techniques should have easily been able to reach a strength of 4000 psi (28 MPa) in the first month. After 10 years in-place the concrete should be even stronger. The level of concrete strength developed by quality shotcrete should easily accommodate drilling in anchors or concrete screws. In my experience it would have been highly unusual to build an entire 10-story building with shotcrete even in the 1960s. I’d suggest based on the extremely weak material properties and the wall turning to dust what you think is shotcrete may be sprayed plaster or stucco. Those materials don’t have near the same strength as shotcrete and would exhibit many of the problems you have mentioned.
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Active Minerals International, LLC
34 Loveton Circle, Suite 100 Sparks, MD 21152 United States
Amelie Construction & Supply, LLC
285 Girty Road, Spring Church, PA 15686, United States
American Concrete Restorations Inc
11S375 Jeans Rd, Lemont IL, 60439-8839 United States
American Standard Concrete Pumping Hawaii Inc
94-400 Koaki St , Waipahu HI, 96797-2874 United States
Sustaining Member
Artisan Skateparks
4600 Tamarack Dr, Kitty Hawk NC, 27949 United States
Sustaining Member
Ashlar Structural – A Halmar International Affiliated Company
421 East Route 59, Nanuet New York, 10954-2908 United States
Basalite Concrete Products – Vancouver ULC
8650 130th Street , Vancouver BC, V3W 1G1 Canada
Sustaining Member
Baystate Shotcrete LLC
67 Forest Street Suite 199 #270 , Marlboro MA, 1752 United States
Bulley & Andrews Concrete Restoration
1455 W 38th St. , Chicago IL, 60609 United States
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