The destructive power of water is playing a key role in a highway improvement project along one of the busiest roads in the UK’s West Midland region.
Jets of water travelling at supersonic speeds are blasting concrete from around bearings in two flyovers on the A4440 Southern Link Road near Worcester.
The jets are so powerful they can tear lumps of concrete bigger than a fist from around the bearings, exposing the steel rebar for the first time since the carriageway was built.
However, in the hands of the experienced operatives from hydrodemolition specialist Aquaforce Concrete Services, they can also be directed with impressive precision to remove just the right amount material.
Aquaforce is working on the project for its parent company, civil and structural engineering specialist Freyssinet, which is carrying out concrete repairs on the existing roadway for main contractor Alun Griffiths (Contractors) Ltd.
Worcestershire County Council is overseeing the £62m scheme to upgrade a 3.5-mile section of the link road connecting the M5 with south and west Worcester, Great Malvern, Ledbury, Upton and Herefordshire.
The project, now nearing completion, has involved the phased dualling of the carriageway and the repair and upgrading of the in situ roadway, including two raised sections over the River Severn and its flood plain.
Aquaforce, a member of the Water Jetting Association, has been working with Freyssinet to release 56 bearings on four abutments and 10 piers along the two flyover sections, so they can be replaced.
Freyssinet engineers jack up the carriageway to unload the bearing. Aquaforce operatives remove the concrete. The bearing can be taken out. The concrete is then reinstated, and a new bearing installed.
Their success demonstrates the advantages of hydrodemolition in supporting highway maintenance tasks, said Aquaforce General Manager Gavin Thomas, a member of the WJA’s technical committee.
He added: “Our operatives are exposed to almost none of the hand arm vibration (HAV) risks of mechanical tools, and water jetting causes no vibration damage to the structures we work on.
“Particles released are held within water, so dust pollution and highway visibility hazards are reduced. Also, structures like rebar are not damaged and surfaces need little or no further preparation before being reworked.”
The handheld jetting guns are set at an average pressure of 1100 bar (17,000 psi) and a water flow rate of 48 litres per minute.
Wastewater is filtered to remove a significant percentage of suspended solids and pH balanced on site to ensure it can be disposed of safely and correctly.
Each abutment and pier has four bearings. On average, one bearing can be undermined ready to be released every shift, a task that involves removing approximately one metre cube of concrete.
It is a level of productivity that no other methodology is likely to match, which is why hydrodemolition has become the standard method to release bridge bearings in the UK.
Safety is a key consideration. Aquaforce’s operatives wear the latest water jetting suits made from the same material used in bulletproof vests, plus steel-lined boots, and visored helmets.
The WJA’s class-based safety awareness course and practice modules, accredited by City & Guilds, are designed to give operatives the fundamental knowledge and skills they need to begin their water jetting careers.
Now operatives and their employers can benefit from a new WJA course, the world’s first competency qualification for water jetting.
Accredited by ABBE, the Level 2 Water Jetting Technician Certificate, adds a substantial period of work-based assessment (at least a year) carried out by a WJA-approved assessor.
Talk to the WJA about water jetting. Email This email address is being protected from spambots. You need JavaScript enabled to view it.. web www.waterjetting.org.uk. Phone +44 20 8320 1090.
