HR Wallingford, Oxfordshire

Challenge             

The main building work by Dean & Dyball, included the construction of three wave basins, one an impressive 75m by 32m. Equally challenging, at 60m long and underground, was a multi-functional sump tank, with two parallel wave flumes by Toureen Contractors. The concrete design specification was required to meet BS 8007(1) to ensure the total water-tightness that would guarantee the accuracy of modelling results for HR Wallingford’s engineers.

Solution

Featuring multiple sumps, up to 2m wide and ranging in depth from 1.5m to 2.5m, the underground tank made additional demands on the concrete solution. One of the sumps provides volumetric measurement, requiring dimensional precision in the casting, while the tank as a whole needed to be water-tight against high ground water levels. Equipped with a wave generator, viewing windows and gate, the two flumes are identical in size, at 45m by 1.2m by 1.7m deep, with 300mm thick walls and 350mm deep base slab, all reinforced.

BBA approved, not only did PUDLO assure totally watertight, corrosion-resistant structures, it also eliminated the need for a membrane or drainage system, making it ideal for the application. All three structures were achieved using the same concrete mix, thanks to the additional performance characteristics offered by PUDLO modified concrete. These include a minimum 10% strength increase, reduced water absorption, permeability and drying shrinkage, as well as improved dimensional stability and durability which was all-important on the project.

As well as meeting a high specification of surface finish, Toureen needed to adhere to strict criteria for both line and level in achieving the minimum 50mm of cover required throughout. Tolerances for all three structures were just + 2mm in all dimensions. On the wave flumes, in particular, the client needed as smooth a surface finish as possible, as any lumps or nodules on the walls would disrupt wave formation and adversely affect research results. Enhanced workability of PUDLO enabled Toureen to achieve the specified ‘Type C’ plain concrete finish with the absolute minimum of making good once the formwork had been struck.

PUDLO’s comprehensive service support was another factor in the success of the tanks, which passed HR Wallingford’s own rigorous testing. The use of PUDLO additive is project-managed by experienced technicians who ‘quality control’ the product’s application, from concrete design, batching and mixing, to site preparation, pours and post-cure.

Result

Built at a cost of £3.5 million, the 11,200m² Froude Modelling Hall, named after the Victorian pioneer of hydraulic scale modelling, extends the world-class test facilities at the UK headquarters of leading engineering research specialist, HR Wallingford. The purpose-built and environment-controlled hall contains a series of state-of-the-art wave flumes, basins and tanks for the physical modelling of structures and hydraulic features.

The results support the design of a range of structures, from small seawalls to large port and LNG developments. It was therefore imperative that the new facilities were constructed to exacting standards of structural integrity, watertightness and dimensional accuracy to support the reliability of evaluative data.

Dr Keith Powell, Director of HR Wallingford said: “The integrity of the research carried out in our modelling tanks and flumes relies in part on the integrity of their construction and finish. PUDLO additive has been a key ingredient in achieving the structural performance, watertightness and constructional accuracy of these critical concrete structures. It will also provide enhanced durability and assure dimensional stability for many years of testing to come.”