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Inspections of concrete structures
Inspections and maintenance of concrete chimneys, high voltage pylon footings, imprevious floors, on-site quality control.
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Inspections
The quality of a concrete structure is vitally important. For
one thing, the renovation or replacement of buildings and
installations can be very costly. What is more, concrete structures
have to meet exacting safety requirements. KEMA has many years’
experience specialising in the inspection, condition monitoring and
certification of engineering structures. Building and installation
managers and the suppliers of construction products all benefit
from our support and advice. Our expertise covers systematic
maintenance, economic viability, environmental impact, the
durability of materials and the application of process residues in
the production of construction materials.
Dedicated inspection techniques are used to determine the
condition and residual life expectancy of concrete structures in
existing buildings. Inspection-based insight into the condition and
maintenance status of a structure has numerous benefits:- The certainty of objective assessment by independent
experts
- Better specification and planning of maintenance and inspection
activities
- An integrated approach based on multidisciplinary
input
The precise nature and extent of each structural inspection
conducted by KEMA is decided in consultation with the client.
Information about the condition of the structure obtained from the
inspection serves as the basis for developing an effective
maintenance plan. Furthermore, inspection and analysis data are
used by KEMA’s consultants to recommend various ways of tackling
any problems encountered. Where appropriate, the identified options
can also be costed.
Inspection is just one of the services offered by KEMA in the
field of concrete and construction.
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Inspection and maintenance of chimney structures
Operational changes at a plant – switching from ‘dry-stack’ to
‘wet-stack’ operation, for example – can mean that the structural
materials used in a chimney are subjected to stresses unforeseen by
the designers. The result can be accelerated degradation and a
range of associated problems.
Chimney maintenance is often seen as an end-of-the-pipe
activity. In fact, prompt maintenance has considerable operational
benefits, as well as enhancing the safety of the working
environment.
By making expert inspections and providing practical advice,
KEMA can help plant owners and managers to prevent functional
deterioration and the resulting truncation of a construction’s life
expectancy that results from tardy maintenance.
In line with the client’s instructions, KEMA inspects each
chimney structure by reference to the CICIND checklist, DIN
standards and/or specially developed procedures. A full inspection
takes in the chimney’s exterior and lining materials, plus – where
relevant – the cavity area.
On the basis of inspection information about the maintenance
condition of the chimney, minor repairs can be made immediately or
incorporated into a maintenance plan.
To support systematic maintenance programmes, KEMA’s consultants
can on request produce cost estimates, identify optimal inspection
intervals, draw up repair specifications and supervise the
implementation of preventive and corrective activities.
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High voltage tower foundations
Most of the Netherlands’ high-voltage electricity pylons were
erected in the 1950s. When they develop problems, simple repair
work is usually all that’s called for. Standing beside the A12
highway that links the towns of Driebergen and Veenendaal, angle
pylon number 64 proved to be an exception, however. The
pylon’s owners – regional energy company REMU – had been worried
about number 64 for some years. KEMA studies carried out in
1995 and 1996 revealed that earlier attempts at corrective
maintenance had been unsuccessful or had addressed the symptoms of
the problem rather than the root cause.
KEMA and REMU therefore developed a method for replacing
concrete pylon footings in difficult locations. Then, having
struggled with the recalcitrant number 64 for years, REMU
called in KEMA to help organise a pilot project to try out the new
method. The bottom line was that the work had to be done without
interrupting power supplies or interfering with the movement of
traffic on the A12.
The engineers had little room to play with. The pylon stood at
an angle, on the side on an embankment. As a result, it wasn’t
possible to use a guy cable for temporary anchorage. Working from
KEMA drawings, REMU accordingly constructed a reusable support
frame, designed for easy attachment, detachment and relocation to
other sites. This frame was used to secure the pylon while its
footings were broken up and replaced. Designing and constructing
the support frame was quite an undertaking, involving the
development from scratch of a special safety and accommodation
protocol. The entire process eventually took four months, spanning
design, demolition, concrete mix selection, test block preparation,
adhesion surface checking, concrete pouring, removal of the
shuttering and hardening of the concrete. Within this period, the
realisation phase took about two weeks.
KEMA advised REMU on selection of the optimum concrete mix.
Dating from 1951, the original concrete simply hadn’t been up to
the job. Not only did the workmanship leave much to be desired, but
also several different types of cement had been used, not to
mention a reactive aggregate (ASR). Following testing of
alternatives, two concrete repair mixes were chosen, which
underwent performance testing in KEMA’s laboratory.
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Imprevious floors
An impervious floor has to be reliable and an effective barrier
to fluids. Owners and managers of buildings and installations with
impervious floors need to be sure that they are meeting their legal
obligations. That implies independent inspections by experienced,
knowledgeable engineers. KEMA offers assessment and inspection
services for soil-protecting structures at industrial sites,
factories, facilities for motor vehicles, residue stores, sludge
depositories and agricultural establishments. As well as inspecting
such structures, KEMA undertakes damage assessments where
appropriate and makes technical evaluations. As an independent
consultancy and research body, KEMA has decades of experience
inspecting and advising on the corrective maintenance of impervious
installations.
Compliance with environmental legislation is subject to
government supervision. Businesses responsible for impervious
installations are required to meet the requirements laid down in
the Soil Protection Facilities Plan (PBV), for example. Assessment
guidelines and CUR/PBV Recommendation 44 (Assessment of
Impervious Facilities) set out what must be done to satisfy these
requirements. Drawing on its extensive experience in this field,
and acting as one of the sponsors of the VABOR Impervious
Facilities (VDV), KEMA is active in the inspection and assessment
of facilities covered by the various regulations.
During the inspection of concrete floors, data is recorded on
standardised forms. Using an inspection method developed by KEMA,
expert engineers carefully assess the durability and (residual)
life expectancy of a structure. On request, an inspection report is
also prepared for the client, covering repair methods, finishing
treatments and structural integrity and stability. Such reports are
particularly valuable in the context of proposed property
purchases, for example.
Our inspectors meet the expertise requirements of PBV report
WF-9801. Where an impervious floor is found not to satisfy the
applicable criteria, further tests can be conducted in KEMA’s
STERLAB-accredited laboratory on the basis of, for example, CUR/PBV
Recommendation 63.
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On-site quality control
KEMA can prepare a plan covering quality control
during the realisation phase of a construction project. This plan
details what checks are to be performed and when. Once the work
starts, site inspections are conducted to ensure that the
construction activities are proceeding in accordance with the
project’s quality plan. In addition, the contractor’s quality
checks are verified on a random basis. Finally, the finished
structure is checked against a specification checklist to make sure
it meets the client’s requirements.If problems are detected in the course of the site inspections
or verification checks, these are noted on a special nonconformity
form and copies given to both the client and the contractor. The
contractor is then asked to indicate the proposed corrective action
on the form. Once the proposals are received, KEMA advises the
client on the likely effectiveness of the measures and on any
financial implications (arising out of work volume discrepancies,
for example).
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