GeneralQ When was the 4000 psi (28 MPa) standard set for shotcrete?
ASA has taken the position that structural shotcrete is shotcrete that meets or exceeds a compressive strength of 4000 psi (28 MPa). Looking at pertinent ACI Codes related to watertight concrete, as we would expect in a pool, we find ACI 318-95, “Building Code Requirements for Structural Concrete,” introduced a provision in 1995 that required: “Concrete intended to have low permeability when exposed to water shall have a Minimum f´c of 4000 psi (28 MPa)”. Similarly, ACI 350-01, “Code Requirements for Environmental Concrete Structures,” first issued in 2001 required: “Concrete intended to have low permeability when exposed to water, wastewater, and corrosive gases shall have a Minimum f´c of 4000 psi (28 MPa)”. Since ACI 350 is more directly applicable to water-containing structures, the 2001 date is probably the most relevant, though ACI 318 introduced the concept in 1991. We do, however, see shotcrete specified at lesser levels for different types of uses.
