A417 Gloucester Bypass
Contractors seeking a lightweight infill for a bridge abutment on a £18 million by-pass scheme identified Leca® lightweight aggregate as the optimum solution for speed and cost.
Main contractor Norwest Holst Construction Limited used some 840m3 of Leca® expanded clay aggregate to provide the infill behind sheet piling for the northerly abutment of the twin span Castlemeads Bridge which carries the new A417 Gloucester South West by-pass over the River Severn.
Initially, polystyrene-based fill had been considered for the project but in a value engineering review maxit Leca® emerged as the preferred option, both for cost effectiveness and convenience. The material can be fully submerged and is free-draining, making it ideal for applications adjacent to watercourses.
The sheet piles were retained using tie rods, which were installed in perforated ducts to protect the rods and assist drainage. Leca® in 10-20mm rounded pellets was then tipped in 60m3 loads prior to compacting using traditional infill methods.
A spokesman for Norwest explained: "Earlier in the project we used polystyrene but it is difficult to handle and needs protection from contaminants such as diesel. A value engineering exercise showed us that using Leca® made commercial sense because it provides a quicker and more cost-effective solution."
Leca® is approved for both general fill and structural backfill applications by the Highway Agency.