Fillmaster expanded polystyrene provided the perfect fill material for raising the floor level at the new Royal Mail East London Network Hub, which is being built in Thurrock in Essex. The old sorting office, which was based on a site required for Olympic development therefore had to be relocated and the floor level on the new premises needed to be raised to the same height as the rear of the trucks for ease of loading.

In total 3,000m³ of Fillmaster 150 E was supplied for the dock leveller, which was cut to the specific sizes required in order that the new floor suited the required truck height. The material was supplied in two layers of 535mm deep, which were loose laid and covered with a damp proof polythene membrane and topped off with a 150mm thick concrete slab. The Fillmaster product was installed on site in the new building within four days by main contractor Fitzpatrick.

The location of the new sorting office, relatively close to the River Thames, meant that the underlying ground, consisting of predominantly silt and clay deposits, would be unable to withstand heavy loading created by traditional fill materials. In these conditions, the fill material would have caused high levels of settlement, with possible implications for the existing foundations. The specifiers were therefore looking for a lightweight substitute to traditional fill that would still enable them to achieve the brief.

Expanded polystyrene (EPS) in the form of Fillmaster proved to be the perfect solution, because it has an extremely high strength to weight ratio, ensuring that it did not add undue pressure on the underlying structure. The lateral forces generated by the traditional fill would also have created outward pressures on the perimeter wall and again Fillmaster was able to address this issue.

Curtins Consulting in Leeds determined that traditional fill materials would have been far too heavy if used on this project, simply because of the wetland ground conditions. It would have resulted in the building becoming unstable and, over time, would have led to it sinking into its foundations. As they had specified Fillmaster before, they knew that it was ideal for reducing loads on existing foundations and was a lightweight material that would stabilise the building and also minimise the burden on perimeter walls.

Jablite states that Fillmaster was the best solution for this project because of the fact that it is has such a high strength to weight ratio. Fillmaster provided a very effective method of achieving the required infill to raise the floor, which makes loading and unloading of trucks so much easier.

Fitzpatrick, the project contractor, found Fillmaster quick and easy to install and much more practical than traditional hardcore infill, which would have required many more deliveries to site and specialist handling equipment. They again had worked with Fillmaster before and the job was completed quickly and with few complications.

Fillmaster is available in a range of different grades to accommodate varying load bearing requirements. The product also helped to minimise the environmental impact because EPS does not absorb water which means that it eliminated the possibility of leaching often associated with traditional fill materials.

Expanded polystyrene has been used for over 30 years in the construction of roads, for bridge abutments, bridge underfill, noise bunds, retaining walls, soft and hard landscaping and a whole host of other ground and civil engineering applications.

EPS scores zero both for ODP (ozone depletion potential) and for GWP (global warming potential), making it the perfect environmental choice. In addition, EPS has been given an “A+” rating in the BRE’s Green Guide to Specification.

To enable the construction of two connecting slip roads it was necessary to widen an existing underpass by 20m either side of the existing Edinburgh City bypass. As the original structure had been designed to carry only the fill which formed side slopes, it was necessary to consider the additional imposed loads. Rather than strengthen or replace the existing structure, it proved economical simply to reduce the dead loads by incorporating Fillmaster in the design.

The reduction in dead loads acting on the structure by using a fill with a density of less than 30kg/m³, enabled the live loads to be increased with no detrimental effect to the extended structure.

In all, 2,000m³ of Fillmaster blocks were used in three grades to replace structural backfill on a 30m stretch of the road. The 2440 x 1220 x 610mm blocks were delivered on vehicles carrying 70-100m3 per load enabling rapid construction without the need for compaction.

Client: Scottish Office
Design: W.A. Fairhurst
Contractor: Balfour Beatty
Volume: 2,000m³