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
Thorcon Shotcrete & Shoring LLC
10900 Chatfield Lake Road, Littleton CO, 80125 United States
Sustaining Member
Top Gun of Virginia Inc
10017 Richmond Hwy, Lorton VA, 22079-2421 United States
Sustaining Member
Torshot Construction Limited
5369 Maingate Drive, Mississauga Ontario, L4W 1G6 Canada
US Concrete Products LLC
16 Greenmeadow Dr, Ste 202, Timonium, MD 21093-3231, United States
Sustaining Member
Valme North America Inc.
2701 Nicholas Rd., Franksville WI, 53126 United States
Vancouver Shotcrete & Shoring Inc
35920 South Parallel Road, Abbotsford BC, V3G 2K4 Canada
Western Grater Contracting LTD
Unit # 2095 – 2015 Millstream Rd., Victoria British Columbia, V9B 6E2 Canada
Sustaining Member
Western Shotcrete Equipment
3026 S Scott Ln # 5096, West Haven, UT 84401-3397, United States
Wurster Engineering & Construction Inc
34 Carrie Drive, Greenville SC, 29615 United States
Zolula (Pty) Ltd
26 Quantum Street
Carpe Diem C10, Techno Park Stellenbosch, 7600 South Africa
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