June 2010 - NHBC Home

Issue 47
June 2010
Glassfibre Reinforced Concrete (GRC)
GRC was first introduced in the early 1970s and is now used on some of the world’s largest
and most prestigious building projects. In the UK, use of the material by house builders and
developers is growing, both as a cladding solution and as a lightweight and durable alternative
to traditional cast stone dressings.
It is essential that GRC is correctly
designed and manufactured for its
intended purpose with appropriate
quality control procedures in place.
GRC is a cement-based composite,
reinforced with special alkali resistant
glass fibres, which are blended
throughout the concrete matrix to
give a material which displays a high
resistance to tensile, bending and
impact forces.
GRC products may typically be only
12-15mm thick, formed using thin wall
casting or spraying techniques. The
weight of GRC products is considerably
less that than their conventional
counterparts which helps with handling
and installation. The nature of the
material provides good resistance to
damage at edges and corners.
Traditional concrete is classified by
its compressive strength (i.e. C40),
GRC is classified by reference to
its characteristic flexural strength
(termed in the industry as Modulus
of Rupture or MOR). For convenience
of specification, GRC is graded into
three categories, Grade 8, Grade 10,
and Grade 18, each grade representing
numerically the characteristic MOR
value. Correct GRC manufacture
requires that a regular testing regime
is operated to measure and record
MOR values (and other parameters)
on a continuous basis.
GRC in the UK will typically be
manufactured in accordance with the
best practices developed in Europe,
America, Asia and Australasia over
the last forty years. The International
Glass Reinforced Concrete Association
‘Specification for the manufacture,
curing and testing of GRC products,
Third Edition – March 2010’ is an
important reference for ensuring good
quality GRC. This is consistent with,
and refers to, national standards BS
EN 1169 and BS EN 1170: 1998 parts
1-7. A copy of the specification may
be downloaded from the websites
ACTION
of the GRCA (http://www.grca.org.
uk/technical/downloads.asp) or the
Concrete Society.
To ensure satisfactory in-service
performance products must be
designed to ensure adequate strength
and appropriate fixing. The test data
obtained from regular test results of a
manufacturer is essential in validating
the values used in design. This is
particularly important for built-in items
such as heads and band courses or the
larger cladding panels which may be
formed in GRC.
When selecting a GRC product the user
must ensure that design will be carried
out in accordance with the relevant
national standards for any intended
profile or panel form, including the
design of the fixing systems used to
support or restrain GRC items. It is
equally important to ensure that the
manufacturer has access to both the
facilities and procedures to carry out
the testing required in the manufacture
of GRC, or alternatively has in place
arrangements for third party testing.
The Glass Reinforced Concrete
Association operates an ‘Approved
Manufacturers Scheme’ whereby
participating companies have
demonstrated to the Association
they have the procedures, plant and
equipment to comply with the required
specifications and standards. For
further details about the GRCA and
its Approved Manufacturers Scheme
please visit www.grca.org.uk
If you are proposing to use GRC products make sure they have been
designed and manufactured in accordance with recognised standards
and that the manufacturer is a member of the GRCA scheme.
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