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Description / Abstract:
INTRODUCTION
The purpose of this report is to present procedures that can be
used to evaluate the quality and properties of in-place
shotcrete.
Considerable literature is available on testing fresh concrete,
concrete specimens, and in-place concrete. Procedures for the
production and testing of concrete are covered by ACI and ASTM
Standards. The development of in-place (nondestructive) test
procedures for evaluating concrete structures has progressed to the
point where the use of such procedures has become common
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 506.2 requires
preconstruction testing to verify a nozzleman's ability, such
testing is not always done. Additionally, inspectors who are
knowledgeable in shotcreting are not ordinarily available to
monitor shotcrete quality. Thus, if properly skilled nozzlemen are
not used, defects such as improper encasement of reinforcing steel,
voids behind steel, excessive cracking caused by shrinkage, sand
pockets, and defects caused by inclusions of overspray and rebound
can occur.