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
Cancrete Equipment Ltd
1810 Meyerside Drive , Mississauga ON, L5T 1B4 Canada
Sustaining Member
CCP Shotcrete + Pumping
15401 Dexler Dr , Austin TX, 78734-2724 United States
Sustaining Member
Coastal Gunite Construction Company
PO Box 977 , Cambridge MD, 21613-0977 United States
Condon-Johnson & Associates Inc
Ste 200, 480 Roland Way , Oakland CA, 94621 United States
Sustaining Member
ConForms
777 Maritime Drive , Port Washington WI, 53074 United States
Sustaining Member
CONSOLIDATED SHOTCRETE INC.
700 FLINT RD , NORTH YORK ON, M3J 2J5 Canada
Sustaining Member
COST of Wisconsin, Inc.
4201 Highway P Jackson, WI 53037 United States
Cruz Concrete & Guniting Repair Inc
1405 Winesap Dr , Manasquan NJ, 08736-4020 United States
Sustaining Member
Dees Hennessey Inc
200 Industrial Rd Ste 190 , San Carlos CA, 94070-6257 United States
Deluxe Shotcrete & Concrete Construction
PO Box 385 , Santa Rosa CA, 95402-0385 United States
Engineering & Construction Innovations, Inc.
7002 6th Street N , Oakdale MN, 55128 United States
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