The Omni Centre Car Park is a popular shopping centre underground car park, located in Edinburgh, Scotland. Over time, the car park had succumbed to structural damage and corrosion caused by ingress of de-icing salts from above ground and traffic movements.
Corrosion-related issues are extremely common in reinforced concrete structures such as underground parking, due to the cover becoming contaminated with chlorides, carbon dioxide and simply water intrusion.
A comprehensive corrosion management strategy
C-Probe were sub-contracted to Makers Construction to provide a long-term, sustainable solution in both operation and materials for the parking structure designed from data arising from a full condition survey.
100% corrosion potential mapping was undertaken to the decks and ramps, and also 3D through depth half-cell potential profiles by Structural Healthcare for the client team lead by Waterman Structures.
This survey highlighted risk levels of corrosion activity within deck levels and ramps and how those differ in risk to different levels. Parallel measurement of carbonation, chloride depth contamination and concrete cover to reinforcement collectively provided the basis for designing the corrosion management scheme for tendering the project.
The different risk profiles lead to an interoperable approach to corrosion management with the targeted use of surface-applied corrosion inhibitor treatment, galvanic anode protection to new concrete repairs and impressed current cathodic protection (ICCP) system aimed at addressing the differing risk profiles to engineer a cost-effective resilient system solution.
C-Probe took this survey and tender design to provide product and service support for the implementation of 42 ICCP control and monitored zones +chase® anode mortar and 7 additional monitoring zones installed for levels protected using surface-applied corrosion inhibitors and C-Puck® III galvanic anodes activated with low carbon LoCem® CPM.
LoCem® +chase® operates as an ICCP mortar anode installed within chases cut in the deck surfaces. Implementation of C-Probe’s range of AACM geopolymer products complies with Environmental Social Governance (ESG) policies due to LoCem®’s low carbon credentials and sustainable longevity of use.
Due to its bond strength to concrete as a mortar it offers reduced risk in its installation method to the parent concrete as well as operational performance due to no bond break, enhanced acid resistance and current capacity.
LoCem® is manufactured from industrial wastes with no heat and reduced water content yielding up to 90% less CO2 emissions compared to CEM 1 and at a carbon value of only 0.05kg CO2e per kg produced.
In addition to this, over 6,500 C-Puck galvanic anodes were used to protect newly repaired areas to 2 levels to cater to the different degrees of corrosion activity on the various levels.
A traditional approach to restoring a parking structure may involve consideration of demolishing and reconstructing the parking decks with new steel and concrete – using CP continuously protects the structure whilst offering a non-invasive protection method that minimises construction materials and waste sustainably with resilience built-in to the structure.
Futureproofing reinforced concrete
The anode system is controlled with data from embedded sensors accessed remotely through the C-Probe network management technology, AchillesICP and AchillesIES, giving a permanent record of the structure’s performance.
C-Probe’s approach to restoring the Omni Centre Car Park was sustainable in its materials, economics and operation.
Reconstruction was also a near-impossible strategy due to underground facility and electric tramlines on land, meaning a non-disruptive interoperable corrosion management strategy and specialist implementation with Makers Construction was essential to minimise social disruption and successfully increase service life for a significant length of time.
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