Case Study - Redbridge ViaductMonday 1st March 2021 1:40am
Redbridge Viaduct is a 50 year old bridge carrying westbound traffic out of Southampton over Test Lane, the railway and the River Test. A potential structural issue with the bridges was made apparent after an independent report had found them to be in “significant poor condition”, with the main damage appearing within the concrete underneath the structures.
The viaduct is 270 metres long and is supported on nine reinforced concrete wall supports and 106 columns. Due to its age, the harsh marine environment and the large volumes of traffic that use the viaduct daily, Hampshire County Council announced that essential repairs to the concrete supports would need to be carried out.
Hampshire County Council initially appointed Skanska, a multinational construction and development company based in Sweden, to manage the repair work on the Redbridge Viaduct which started in early 2020. Skanska have since sub-contracted the specialist concrete repair works to Concrete Repairs Ltd (CRL), who are one of the UK’s leading specialist asset maintenance building and structures contractors.
These repair works are part of a much wider project to refurbish all four structures carrying the A35 Redbridge Causeway, and follows the first phase of the project which was completed in 2018. This initial repair was to replace leaking carriageway and footway joints which were leaking and causing water to run down the supports and columns underneath the viaduct, as well as a complete resurfacing of the roads.
The 2020 project will be undertaken in phases and will take approximately 18 – 20 months to complete, this is mainly due to the scale of the project alongside the fact that the repair work is highly weather dependant.
This will include repairs to:
- Redbridge Viaduct, which carries the A35 Westbound carriageway between M271 Redbridge Roundabout and Totton.
- Redbridge Road Bridge, which carries the A35 Eastbound carriageway over Test Lane/Old Redbridge Road, Southampton.
The concrete repair work will protect over 100 supports of the Redbridge Viaduct and Redbridge Road bridges and will be carried out in a sequence of removal and localised patch repairs in order to avoid the need for temporary propping and carriageway closures of the road above. A cathodic protection system will also be installed to effectively prolong the life span of the existing structures.
Hampshire County Council, Skanska and CRL, together with leading specialist material manufacturers’ Weber Saint-Gobain and Fosroc specified a system which would repair and protect the viaduct for the next generation.
Resapol, the UK’s leading specialist construction chemical distributor has helped with the supply and service required for this massive project despite the limited storage space available on site. Resapol’s local branch in Southampton have been able to supply materials on a same day basis to ensure the project runs on schedule and without delay.
Resapol have currently supplied webercem five star repair concrete CP and webercem mortar CP for the patch repairs of the existing concrete and to provide cathodic protection for the reinforcement in the structure.
William Sinnott, the Senior Contracts Manager at CRL commented: “Resapol have been competitive, resourceful and have provided a great service between the site team and material manufacturers”.
webercem five star repair concrete CP is a cementitious repair concrete which fully complies with the Highways England Specification for Highway Works Class 29F high-strength flowing concrete. webercem mortar CP is a pre-batched, single-component mortar that produces a render with low resistivity. Both weber materials conform to BS EN 1504-3 as Class R4 repair products and are suitable to repairs on concrete structures where cathodic protection systems are to be used.
For the large area of repairs such as the column supports, Fosroc’s Renderoc DS & DSR dry spray materials have instead been used. Renderoc DS & DSR are rapid setting dry spray materials with low rebound, which results in high productivity as well as significant savings in costs. Renderoc DS & DSR also conform to the requirements of Highways England, Standards for Highways, Specifications for Highways Works, clauses 5703, 5704, 2717 (Spray Applied Concrete Repair Materials) and 1704.5 (Control of Alkali-Silica Reaction).
All of these factors make the chosen materials the perfect blend of an effective and cost saving solution.
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