News
Freyssinet Complete Further Works Under Highways Agency Framework
31 January 2012
Freyssinet Limited are continuing to work successfully in collaboration with other specialist contractors under the Highways Agency Area 9 & 10, Construction Management Framework.
The CMF is a collaborative approach to maintaining £75billion worth of assets for HA in these areas over the next 4 years. It consists of a number of different contractors from different specialist areas who work together to deliver network improvement and maintenance schemes on the all purpose trunk road and motorways in Highways Agency Area 9 and 10, which covers much of the West Midlands and North West.
Bromford Viaduct is one of a number of viaducts forming the Midland Link Motorway Viaducts (MLMVs). There are 21km of elevated motorway comprising 1200 no. cross beams and 3600 no. columns, constructed between 1969 and 1972.
During the mid 1980s corrosion started to occur due to de-icing salts leaking through deck expansion joints onto cross beams. Initial preventative measures, such as placing gutters beneath the expansion joints, were implemented during the mid – late 1980s and repair works in 1990. Concrete repair and cathodic protection schemes have been on-going to the present day based on calculated intervention dates for each cross beam. Repair Contract 153 (R153) commenced in January 2011 and comprises of 8 no. cross beams. With Amey acting as Principle Contractor, Freyssinet Limited was appointed as a specialist contractor within the Highways Agency Area 9 &10 CMF.
The scope of works involved removing sections of concrete to be repaired by saw cutting and hydrodemolition, undertaken by Freyssinet’s own in-house hydrodemolition team. Repairs were carried out as necessary to reinforcement steel, and the areas re-instated using flowable concrete, with some beams repaired under a supported condition.
Cathodic protection to 2 no. beams involved the installation of Galvanic (Sacrificial) anodes, whilst the remaining 6 no. beams had an Impressed Current Cathodic Protection (ICCP) system installed. The ICCP was designed as a 3 no. zone system; zone 1 to the shear walls being a ribbon mesh primary anode with a spray applied conductive overlay, zone 2 to the beam top and upper section of the beam sides being a ribbon mesh anode with non-conductive repair mortar overlay, and zone 3 to the lower section of beam sides, beam soffit and top of columns being a similar system as zone 2.
Technical issues which prevented supporting steel work being erected to underside of 2 no. cross beams threatened to cause delays to the programmed works, and Freyssinet’s installation of the CP system in particular. Successful cooperation between all parties resolved this situation, and the works were re-sequenced to enable Freyssinet to begin installation works ahead of programme by utilising concrete curing periods where there was no other activity taking place in the work area.
The designers also re-sequenced concrete repair works so that as far as practical, whichever half of each beam needing least repair was concentrated on in initial repair stages and would be complete in advance of the other half of beam, freeing up nearly 50% of CP installation work to be done before completion of concrete repairs. This method was applied to all beams where programmed work extended beyond Christmas 2011.
Utilising Freyssinet’s own in-house hydrodemolition team contributed to the success of the new programme. Where concrete surface hydro-prep was required for overlay material, the team was able to mobilise immediately, taking advantage of short durations of concrete curing time, all the time pulling back the programme.
The cathodic protection on R153 was commissioned with performance verification taking place 45 days after ‘switch-on’ in early December 2011.
Successful cooperation between all parties resulted in the programme being pulled back to mid December 2011, offering the client savings in terms of both time and money.