Watertight construction, sealing against waterpressure, joint sealing, cold joint sealing, membrane sealing, waterreactive Membrane, structural waterproofing

1. RCSI choose cutting edge waterproofing solution for York Street
With a basement depth of 17 metres, the sub-structure is exposed to negative
water pressure in excess of nine bar.
CEMtobent CS Plus is purposely engineered for horizontal as well as vertical
Structural Waterproofing. A unique PE honeycomb structure evenly distributes and
controls the swelling of the water-reactive bentonite.
Over 9 bar waterpressure
manifesting itself pre-pour
The Patient:
When completed this near 8,000m2 Education &
Research facility will have 5 floors over ground and 4
floors below ground level, excluding substructure, with
an estimated construction cost of €23 million. The
basement depth is 17 metres and the sub-structure
will be exposed to negative water pressure in excess
of nine bar. Building Contractors, Michael McNamara &
Company commenced work in late December 2007 on
enabling works in relation to the construction of the sub-
structure.
The Diagnosis:
As the sub-structure is to be exposed to very high levels
of negative water pressure (> nine bar), the choice of
structural waterproofing system was critical. First and
foremost the waterproofing system must be able to
withstand the very high water pressure and maintain
its integrity. The system needed to be flexible enough
to meet the demanding challenges of the sub-structure
construction. Secondly, quality and confidence in
the efficacy of the system was an important factor in
the specification decision of the design professionals
associated with this project. All component products of
the overall system had to carry CE certification and have
a visible track record of performing in these demanding
conditions.
The Remedy:
IBC, one of Ireland’s leading suppliers of structural
waterproofing systems, worked hand in hand with the
project engineers and architects to devise a suitable
waterproofing system for this structure. As the system
had to have flexibility it was decided to incorporate
various waterproofing technologies rather than be
limited to one proprietary technology which could not
deliver all requirements.
The Royal College of Surgeons, their Architects, Brian O’Halloran & Associates, and Consulting Engineers, JB Barry
& Partners, opted for the intensive-care approach to safeguarding the impermeability of their new Educational &
Research Facility at York Street, Dublin 2, which is currently under construction.
One of the key characteristics of the specified materials was their ability to be applied in all weather conditions. The first decision was to use
CEMtobent CS Plus, a unique three layer geocomposite clay liner (GCL) bentonite membrane as a waterproof barrier for the walls and floor slabs.
Unlike most of the other bentonite liners available on the market CEMtobent CS Plus is specifically designed as a waterproofing membrane
Construction joint featuring Cemflex VB Steel plate
Waterbar. The crystallization coating does not react
despite abundant site water
for below ground reinforced concrete structures. The
CEMtobent CS Plus is placed at the water-side of the
reinforced concrete and becomes active in contact with
the water. When unconfined bentonite comes in contact
with water it is capable of swelling to more than 12 times
its dry volume. The CEMtobent CS Plus system ensures
there is controlled swelling of the bentonite and therefore
providing a dense, impervious waterproof membrane.
CEMtobent CS Plus has a number of other important
advantages in that it can be applied in any weather
conditions, is root resistant and most importantly radon-
tight.
The ground anchors were detailed with Maxseal Super;
a cement based waterproof coating with crystallisation
and osmotic properties. A layer of Cemtobent Paste
was placed over the Maxseal Super coating and the
Cemtobent CS membrane was fixed tightly around the
base of the Anchor.
In every waterproofing specification the most critical
points are those with the greatest perceived weakness;
the joints. A combination approach was adopted for the
joints in York Street. CEMflex VB plate, the revolutionary
steel plate waterstop with a patented crystalline coating
on the both sides and inbuilt rain protection was used to detail the horizontal construction/day joints. CEMflex VB plate is an active steel
waterstop. The sealing function is based on an active crystallisation process as well as supporting the natural sintering process of concrete.
Requiring only 30mm of concrete cover on both sides, the CEMflex VB Plate is simple to install and dramatically reduces the labour time
typically associated with traditional PVC waterstops, (up to 80% installation time-saving).
Quellmax Plus, a benonite waterstop tape with crystallisation additives and a patented rain protection coating, was specified for the vertical
construction joints. The patented rain protection system ensures that the product is protected from unwanted swelling during installation and
will be unaffected by water contact for 72 hours. In contact with concrete the patented coating degrades due to the alkalinity of the concrete
and is immediately effective against water ingress. Quellmax Plus works in a two phase approach; firstly, in contact with water it swells to fill
the available void, (swelling capacity >300%), and secondly it seals by the process of crystallisation.