Vacuuming wet cement to save thousands of hours on site

(Photo: Sam Saunders/flickr)

A new piling technique that saves time and material is being used on the HS2 high-speed 2 rail project in the UK.

The new zero trim pile technique uses a vacuum excavator to suck out excess concrete when still wet rather than wait for it to set and then cut it out.

The method is expected to save 60,000 working hours on a single site.

The technique has been developed by piling specialist Cementation Skanska, working for Skanska Costain Strabag joint venture (SCS JV) in London. The suction excavator was supplied by Hercules Site Services.

Lee Piper, a senior works superintendent with SCS, is credited with having identified the opportunity to test a new piling technique,. He worked with Cementation Skanska project director Deon Louw to develop the new approach.

The zero trim pile technique involves sucking out excess concrete while it is still wet, using a vacuum excavator. Traditionally in concrete bored piling, liquid concrete is overpoured and then the excess concrete has to be broken out after it has set. Removing the need to break out excess hard concrete makes the process safer and quicker.

Vacuum excavators are not new, but have not generally been used in this way before. Cirencester-based Hercules Site Services provided a machine for use on site in the Euston approaches. Extracted surplus concrete is retained and reused in construction elsewhere on site, with samples sent off for lab testing.

Lee Piper said: “I have worked in the construction sector for over 20 years, and the same piling techniques have been used throughout that time. Working with colleagues I saw an opportunity to try a new approach and was supported to do so by HS2.

“This technique could be transformational for the construction sector, reducing the health risk that results from breaking piles. The additional benefits of noise reduction, time and carbon savings mean the technique should be attractive for the whole sector to use going forward.”