Seawalls Australia - Benefil

Lightweight Void Fill for Seawalls: New Benefil®

Benefil® fills the erosion voids behind the seawall at Pulpit Point on Sydney Harbour.

Benefil Seawalls quaywalls 1, ,Benefil, Hardschuimvullingen, fills voids, seawalls, retaining walls, culverts, sewage pipes, pipelines, relining, a super-lightweight engineering filler grout, Benefil®, holle ruimte, floor lifting, floorlift, verzakte v The problem confronting Sydney's Hunters Hill Council engineers was how best to grout behind the sandstone seawall at Pulpit Point to compensate for the erosion by harbour tidal action.
The section to be grouted was 40 metres long by approximately 4 metres wide and of varying depth with a total volume of voids of about 40 m3.

Council Chief Engineer, Don Cottie, decided to use a product originally developed for specifically this purpose in Holland, where there are many kilometres of harbour and canal walls, subject to much erosion from the big volumes of marine traffic.


The product was Benefil®, which offered many advantages over conventional solutions.

  • One great advantage was in regard to site access. The Benefil® is foamed on-site from air, water and Benefil® amino-plastic resin. The Benefil® was taken to the site in a small truck. It can be mixed on-site and pumped easily up to 150 metres from the truck and up to a further 50 metres from a single injection point, if required.

    Incidentally, Benefil® is now widely used all over Northern Europe not only for seawall and retaining wall back-fill but also for filling all manner of underground voids including fuel, paint and chemical tanks that are to be ‘abandoned'.

    Another great advantage was the fact of Benefil®'s completely inert and neutral properties in relation to the environment, more than ever critical with work right beside Sydney Harbour. And Benefil® offers a permanent solution; with laboratory tests indicating that it will last at least 150 years if undisturbed and protected from UV.

    On the other hand, it can be removed easily, if required for any reason later, and when intentionally exposed will bio-degrade to completely harmless substances.

    The extremely light weight of Benefil® was also important. It's completely self-supporting and adds only insignificant weight to the structure or sub-base.
    Also of key importance was that application of Benefil® is quite economical, comparing very favourably with conventional grouts, while offering significant advantages over them.