Guide for the Evaluation of Shotcrete (ACI 506.4R-94)

Description

The purpose of this report is to present procedures that can be used to evaluate the quality and properties of in-place shotcrete.

1.2-Considerable literature is available on testing fresh concrete, concrete specimens, and in-place concrete. Pro-cedures for the production and testing of concrete are covered by ACI and ASTM Standards. The development of in-place (nondestructive) test procedures for eval-uating concrete structures has progressed to the point where the use of such procedures has become common.

1.3-Procedures for in-place evaluation of shotcrete have not been well developed or widely used This may be due to the lack of understanding of the difference between shotcrete and concrete. The most important factor in producing quality shotcrete construction is the skill of the nozzleman. While ACI 506.2requires preconstruction testing to verify a nozzleman’s ability, such testing is not always done. Additionally, inspectors who are knowledge-able in shotcreting are not ordinarily available to monitor shotcrete quality. Thus, if properly skilled nozzlemen are not used, defects such as improper encasement of rein-forcing steel, voids behind steel, excessive cracking caused by shrinkage, sand pockets, and defects caused byinclusions of overspray and rebound can occur.