Condition Monitoring System for Reinforced Concrete Structures

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25 Νοε 2013 (πριν από 4 χρόνια και 7 μήνες)

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Condition Monitoring
System for Reinforced
Concrete Structures
Patent pending concrete condition
monitoring system providing ‘real-time’
information on temperature, hydration
and water and ionic movement within
in the concrete cover-zone which
are of relevance in the performance/
durability of concrete exposed to
different environmental actions.

The performance of the surface zone of
concrete (i.e. the cover) is acknowledged
as a major factor governing the
rate of deterioration of reinforced
concrete structures as it provides the
only barrier to the ingress of water
containing dissolved ionic species such
as chlorides. Since concrete is a porous
material, with time, chlorides will
permeate through the concrete and,
ultimately, initiate corrosion of the steel
reinforcement and eventual spalling
of the concrete (see Figure below).
The protective qualities of cover-zone
concrete are thus of considerable
interest to engineers as the service life of
a structure depends, to a large extent,
on the permeation properties of the
cover-zone. Factors such as pore-size,
pore-size distribution, pore continuity,
pore connectivity and pore tortuosity,
which influence the penetrability
of the cover-zone, assume an even
greater significance than strength
alone. Further, the ability to monitor
hydration during the post-curing period,
and the continuously evolving pore
structure within cover-zone concrete,
could be of considerable practical
value as it is the properties of the ‘as-
placed’ concrete which will play an
important role in ensuring adequate
protection of the reinforcing steel.
This is particularly relevant as ‘slower
reacting’ supplementary cementitious
materials such as fly-ash and blast-
furnace slag are now routinely specified.
In-situ monitoring of cover-zone
concrete (i.e. surface 50mm or so)
is therefore critical in attempting
to make realistic predictions as to
The premature deterioration of
concrete structures due to corrosion
of the steel reinforcement is a world-
wide problem, particularly highway
structures subjected to de-icing salt
used on roads for winter maintenance
purposes. In most developed countries,
including the UK, around 50% of the
construction budget is devoted to
repair and maintenance of structures
with over 30% of this expenditure on
concrete structures. In addition, our
infrastructure has now reached an age
where capital costs have decreased, but
inspection and maintenance costs have
grown, constituting a major part of the
recurrent costs of the infrastructure.
Traffic delay costs due to inspection and
maintenance programmes are already
estimated to be between 15%-40% of
the construction costs.
The ability to monitor water and
ionic ingress through the concrete
cover-zone would provide an early
warning of incipient problems
enabling the planning and scheduling
of maintenance programmes, hence
minimising traffic delays resulting from
road/lane closures. The development of
integrated monitoring systems for new
reinforced concrete structures could
also reduce costs by allowing a more
rational approach to the assessment
of repair options; and, co-ordination
and scheduling of inspection and
maintenance programmes.
This system provides such data over
the lifetime of the structure allowing
informed (and timely) preventative
maintenance decisions to be with
greater confidence. The system can be
interrogated remotely.
Distinctly Ambitious
Robert Goodfellow
Technology Transfer
Heriot-Watt University
t: +44 [0] 131 451 3616
Professor W. John McCarter
t: 0131 451 3318
the in-service performance of the
structure. To this end, the remote
interrogation sensor system from
Heriot-Watt will allow continuous
real-time monitoring of the cover-zone
concrete from an office environment.
Although water repellent coatings
(e.g. silane) can minimise water/ionic
ingress, these will deteriorate with
time. Using a self-powered data-link
accessing a network of strategically
placed embedded sensors within
the concrete cover-zone the Heriot-
Watt system could, for example,
inform preventative maintenance
schedules on the condition of the
waterproofing coating on a daily, weekly
or monthly basis (see Figure below).

Informs preventative maintenance
Quality and performance of
waterproofing systems
Tracking moisture/ionic ingress
The requirement for remedial action

Real time measurement of water/ionic
ingress; temperature changes within
the cover-zone can also be monitored

Low cost embedded system capable
of remote operation via wireless

Robust sensors – no moving parts/
zero operator intervention required
The main application is “Whole
Life” condition monitoring and the
preventative maintenance of reinforced
concrete structures such as bridge
piers, wingwalls and abutments etc.
exposed to moisture and/ or salt spray
Proof of Concept has been
demonstrated and data from the on-
going trials at the University marine
exposure test-facility located on the
Dornoch Firth (Northern Scotland) are
The University seeks commercial
partners with an interest in utilising
this patent pending technology within
major civil engineering projects or
in supporting further technology