Arsteinstraumen Bridge, Norway – Underwater Hydrodemolition – Case Study
Remove Marine Growth and Damaged Concrete from Below Crosshead
Sector: Civil Engineering – Transport
Task: Remove marine growth and damaged concrete from below Crosshead to Fjord Bed Level
Location: Arsteinstraumen Bridge, North Norway
When: April – June 2013
Client: Norwegian Highways Agency
Main Contractor: Peab Civil Engineering
Hydrodemolition Sub Contractor: RGL in conjunction with Multibetong
Plant Schedule: Unifloat Barge with crane, Dive Spread, Containerised Hydrodemolition Robot – Power Pack, Column Blasting Rig
This project was tendered in Norway by the Norwegian Highways Agency in 2012 and awarded to Peab Civil Engineering. The Hydrodemolition sub-contract works were placed with Multibetong, RGL’s partner in Norway.
RGL proposed a method for undertaking the works, to ensure all necessary requirements of the tender would be met. Due to the location of the works Multibetong carried out the contract with RGL providing specialist water jetting equipment and developing detailed methodology. RGL’s Commercial Director Jeremy Twigg provided technical support and visited the site several times throughout the duration of the contract.
With the vast knowledge and experience that RGL has compiled over the previous 30 years and due to a number of developments in water jetting equipment now available we were able to provide a suitable methodology for the works to Multibetong. This solution was viewed as the most cost effective and efficient way to achieve the desired results for the Highways Agency. The scope of work required removal of all marine growth and damaged concrete from the bridge columns, preparing them ready for stainless steel reinforcement to be fixed prior to application of a new concrete case.
The contract involved the underwater Hydrodemolition of concrete on twenty-two 1500mm diameter bridge columns, from below the Crosshead to the Fjord Bed Level. This proved a difficult challenge as the work was carried out to a depth of 16m meaning the equipment needed to be robust and reliable working up to that depth.
Multibetong supplied a unifloat barge with crane on which all equipment was positioned. This included a containerised Hydrodemolition robot and power pack, Column Blasting Hydrodemolition Rig, & Generator. A shore based Truck mounted HP Water Jetting Unit provided the water required via high pressure hoses.
Upon commencement of the contract RGL worked along side Multibetong to configure the equipment. Divers placed the Column Blasting Rig in place around the first column as required whilst it was being supported by the crane. The Column Blasting Rig was then trialled, for both traverse speed and working pressure, to illustrate various surface finishes and depths of cut before a decision was made by the client regarding how to proceed.
It was decided that the equipment would operate at a working pressure of 1000bar with 95 litres per minute flow. The rig traverse speed around the column, nozzle standoff distance and oscillation speed were set. The hydraulic equipment would then step down automatically after completing one circumference of the column. This enabled constant work to be carried out on the columns and removed both operators and divers from the workface during the water jetting process. It offered a productivity removal rate of 1-1.5 cubic metres volume per day despite the testing conditions. The productivity was maintained even in poor weather.
This method of undertaking the works removed between 50-250mm of concrete per pass depending on the condition of the concrete. The clients’ requirements were to remove only the damaged concrete. On average each column was completed in 2-3 days. The depth of the fjord was 16 metres meaning as work progressed underwater checks were carried out both by the divers on hand and through underwater camera surveillance to ensure an even finish was achieved across the column.
The project ran for a total of 3 months with all twenty-two columns being treated during this period.
The project was completed on time. Both Multibetong and RGL were pleased with the success and productivity levels attained during the works. Espen Knutsen, Managing Director of Multibetong said “this was a very important time critical project for the Norwegian Highways Agency and we are very happy and impressed with the input and expertise RGL have offered us in this partnership; we look forward to undertaking similar works and to developing our partnership in the future”.
The concrete columns have since been recast resulting in the successful completion of the works.