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.
The ASA Buyers Guide provides a detailed listing of the products and services offered by our Corporate Members.
Sustaining Member
Saffo Contractors, Inc.
3235 Kitty Hawk Road, Wilmington NC, 28405 United States
Schnabel Foundation Company
21355 Ridgetop Circle, Suite 250, Sterling VA, 20166 United States
Shotcrete Africa SCP (pty) Ltd
472 Spionkop Rd Off Boundry Rd, Northriding null, 2169 South Africa
Sustaining Member
Sika Corporation (USA)
201 Polito Ave, Lyndhurst NJ, 07071 United States
Sustaining Member
Sika STM- Shotcrete, Tunneling & Mining (Canada)
555 Michigan Dr Suite 100, Oakville ON, L6L 0G4 Canada
Sustaining Member
South Shore Gunite Pools & Spas Inc.
12 Esquire Road, North Billerica MA, 01862 United States
Sustaining Member
Structural Technologies
10150 Old Columbia Rd, Columbia MD, 21046 United States
Swank Construction Company, LLC
632 Hunt Valley Circle, New Kensington PA, 15068 United States
Terra Engineering & Construction Corporation
2409 Vondron Rd, Madison WI, 53718 United States
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