Concrete Today May 2010 - the Irish Concrete Federation

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concrete today -zero carbon emissions The external edge of the wall was 180mm from the edge of the raft allowing for120mm of insulation to extend down the side of the raft in due course, in the same plane as the 300mm of external insulation would form later in the build. This raft edge insulation would then overlap with the 200kPa insulation underneath the outside raft beam – again, this is done later in the construction process. The first lift was executed very quickly, with full depth lintels supplied by Killeshal Precast Ltd. to save time otherwise wasted making up heights with brickwork. The concrete intermediate floor selected was 100mm wideslab precast flooring from B.D. Flood Ltd., which was designed for use with a 100mm structural screed, although 125mm was used for reasons of levels with receiving steel. Importantly, the wideslab was placed on walls which had a wet mortar bed to help spread load correctly and also to ensure air impermeability between the slab underside and the external wall. Later in the build, the external wall must be sealed internally between where the slab rests and the level of the suspended ceiling, again to ensure air impermeability. Cementicious slurry would be used for this purpose. With the intermediate floor in place, the structural screed was poured and floated and within a few days was ready to support blockwork for the second lift. The roof structure was traditional cut timber rafter, highly insulated and finished in concrete slate tiles supplied by Condron Concrete Ltd. Most of the EPS for the roof was installed at this stage, using a simple jig template and hot wire to cut panels exactly to size. External Finishing Windows and doors, with an overall U value of 0.7 W/m²K, arrived from Haussler in Germany and were fitted to cantilever into the external insulation space. The insulation is then fitted tightly around the windows, with sealing tape connecting window frames to the block wall to avoid the most common form of air leakage. Zero Carbon Concrete House When the insulation is completed, the external render is applied. As this is a new build, as distinct from retrofit, two layers of base course were used to ensure longevity of the render. It should also be noted that super insulated houses requires depths of insulation beyond the normal range provided for in current IAB certification. Though the use of insulation in thicknesses greater than 200mm is not unusual in Europe, only recently has such IAB certification been applied for. In practice, the only difference found on this build was the use of some additional insulation ties around windows and doors which were easily fitted. Problems Encountered Low energy construction needs all aspects of the build to be thought out at design stage, as remedies for problems encountered during construction can be difficult to incorporate. Perhaps the biggest problem was that there are a number of cantilevered balconies which provided a substantial thermal bridging problem as they were part of the intermediate floor slab. The solution was to wrap the balcony in insulation with only stainless steel supports for safety rails allowed through the insulation. Simplicity of form, certainly in roof design, is to be encouraged, as it will minimise the number of points where placing substantial depths of insulation cannot be achieved. At these points, a proprietary textile, its’ 100m thickness equivalent to 50mm of the standard EPS, was used to save space and achieve the required U value. For aesthetic reasons, it was desirable to place the rainwater downpipes within the external cladding. As this compromised the depth of insulation, the proprietary textile insulant was again used to make up the difference to equivalent depths of standard EPS. Air Permeability As the house nears completion, a provisional “blower door” test will be carried out as will thermographic imagery to find any remaining construction weaknesses. It is hoped that the air tightness will be
concrete today - bridge beam construction New developments and advances in bridge beam construction By Peter Deegan, Banagher Concrete Ltd. Precast Concrete Bridge Beams, Banagher Concrete Many advances have been made in both the design and construction of precast prestressed bridge systems in recent years. Probabilistic design techniques and more efficient bridge beams (girders) help deliver faster and more cost effective solutions in leaner times. The range of bridge beams used in Ireland from the 1950’s was the same as that used in the U.K. These beams were developed by the Department of Transport and the Cement and Concrete Association. They are still in use today with the family being made up of the inverted T Beam, M Beam, Box Beam, TY Beam, Y Beam, Super Y and U Beam. Through R & D and continuous investment, Banagher Concrete Limited continually looked at improving the efficiencies of these systems and ways to potentially bring cost savings to the overall Precast Concrete Bridge Beams, Banagher Concrete concrete today 19
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Concrete Today May 2010 - the Irish Concrete Federation

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