Protection against the ingress of water to the three underground floors of a new London hotel, was an important element of the Sir Robert McAlpine contract with Embankment Place Hotels to construct the 203 bedroom Crowne Plaza Hotel, in New Bridge Street, Blackfriars.
Within the system, consisting of a secant pile wall behind an inner concrete skin wall and drained cavity construction, PUDLO was used in a 1 metre to 1.2 metre perimeter strip of concrete to create the required impermeable zone to prevent damp penetrating floor slabs to the public areas below ground. Completely compatible with regular concrete in use by framework contractor, John Doyle Construction, the specially designed mix was supplied to the site by RMC Readymix London from its batching plant in Vauxhall. A feature of the contract was the top down method of construction that took place behind the retained elegant facade of the original building.
To facilitate this process during casting, access holes were left in the slab to enable remaining work to continue on extensive excavation and concrete placement below ground as eight floors of guest accommodation were created in the void above. Despite the problems of creating a watertight structure near to the river, and meeting English Heritage and other planning requirements associated with the preservation of important external architectural features, the net result was that PUDLO was easy to use and entirely compatible with other mixes. The underground areas are dry and warm and no moisture has permeated through the complex substructure.
Using a waterproofing additive it is possible to create a completely water-resistant basement fulfilling grade 3 of the environmental grades for waterproofing (above). The modified concrete is sufficiently watertight to make membranes and drainage systems unnecessary.