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Shotcrete
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 Shotcrete
is sprayed pneumatically onto a surface at high velocity. Known
also as “gunite” and “sprayed concrete,”
shotcrete material is mortar or small-aggregate concrete, placed
on horizontal and vertical surfaces. As the material is applied,
the impact force consolidates the concrete. Shotcrete can be applied
using a wet or dry process, and is used for both new construction
and repairs.
Shotcrete materials are generally the same as those used for conventional
concrete: portland cement, lightweight aggregate, water, and admixtures.
Shotcrete projects also call for the same types of reinforcement
specified for conventional concrete, including deformed bars, welded
wire fabric, and prestressing steel.
Shotcrete is ideally suited for curved or thin concrete structures
and shallow repairs, and can also be used to create thick members,
in commercial and residential applications. Other applications include
swimming pools, grain silos, fire-proofing structural steel, and
many civil engineering structures such as bridges, tunnels, dams,
tanks, and earth retention systems.
Strength and Durability
Shotcrete typically has a density and compressive strength similar
to normal and high-strength concrete, but hardened properties truly
are operator-dependent.
According to the American Shotcrete Association (ASA), in residential
applications, shotcrete mixtures can in fact exceed the compressive
strength of most mixtures used for placed walls. The compaction
that occurs during application of shotcrete helps achieve improved
compressive strength and durability, and low water-cementitious
material ratios of shotcrete mixtures produce other benefits, including
reduced shrinkage and lower permeability.
Supplementary cementitious materials like fly ash, silica fume,
and slag cement may be used in shotcrete applications to improve
workability, durability and chemical resistance. Steel fibers are
sometimes used in shotcrete to improve the flexural strength, ductility,
and toughness.
Industry Resources
This article provides a basic
overview of shotcrete. The American
Shotcrete Association (ASA) offers an extensive
list of publications helpful for those working with shotcrete.
The ASA also answers
more than 50 questions about design and construction with shotcrete.
The American Concrete
Institute (ACI) offers its 506.2-95 Specification for Shotcrete
as a download.
| Publications |
Guide to
Shotcrete (ACI 506R-90) (LT210)
When is shotcrete an economical alternative to cast-in-place construction?
On a high-production job, is the dry-mix or wet-mix process preferred?
What are the equipment requirements and application methods? And
how is shotcrete tested? You'll find answers to these questions
and many more in the Guide to Shotcrete. These 41-pages
are packed full of usable, easy-to-understand directions for building
high-quality, economical shotcrete structures.
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