There are four basic reasons to require preconstruction qualification testing:
- To prove the suitability of the fresh shotcrete mixture design for the intended use;
- To verify the proposed mixture will produce the required strength and any other specified hardened shotcrete properties;
- To prove the ability of the nozzleman (and blowpipe operator, if required) to place dense, homogeneous shotcrete completely encasing the reinforcing steel under field conditions; and
- To prove the desired surface finish can be achieved.
This testing must be discussed in detail with the shotcrete contractor in advance with a clear understanding of the expected outcomes and the process for any required adjustments. Requiring ACI Nozzleman certification is an important requirement in screening for qualified nozzle operators. However, it is not a guarantee that the nozzleman has applied shotcrete under the same conditions to be encountered on your project. Therefore, a preconstruction plan is an important part of critical projects. Other prequalification testing may be necessary depending on the nature of the work.