Title:
Understanding Shotcrete -- Structural Applications
Author(s):
James Warner
Publication:
Concrete International
Volume:
17
Issue:
10
Appears on pages(s):
55-61
Keywords:
mixture proportioning; mortar (materials); nozzles; rebound; shotcrete; water-cement ratio; Construction
DOI:
Date:
10/1/1995
Abstract:
Widespread use of shotcrete in massive placements, thick sections, or heavily reinforced sections has not yet occurred in many parts of the world, including the United States. Many experienced shotcrete professionals often opine that such applications are inappropriate, and often express doubt that such work can be satisfactorily accomplished. In spite of this apparent resistance, the fact is that, through the years, a huge amount of quality structural shotcreting has been successfully performed. Within the writer's experience, reinforcing bars as large as No. 14 with spacing clearance as little as 3 in. (76 mm), have been satisfactorily encased, as have multiple layers of bars as large as No. 6 spaced 6 in. (150 mm) on center. There is abundance of literature describing shotcrete installations where large bars and, in some cases, closely spaced reinforcement, was satisfactorily encased. In 1965, photos of closely spaced No. 14 bars were included in an article describing the construction of a shotcrete retaining wall. In 1973, details of the design criteria for rehabilitation of a ten-story concrete hospital structure, involving reinforcing bars as large as No. 11, were presented by Strand. The shotcreting of new 17 in. (430 mm) thick, 12 ft (3.7 m) high shear walls containing No. 11 bars was described in a 1979 article about seismic retrofitting of a high school building. Case histories describing the details of construction, and including many photographs of heavy and closely spaced reinforcing bars, for four separate structures is presented by Isaak and Zynda. It must be understood that such work requires an exceedingly skillful nozzleman backed by an equally competent crew.