Figure 4: Relationship between relative humidity and corrosion rate of steel reinforced concrete on carbonated mortars dosed with chloride (1mA/m2


- 1um/year) (5)


The Galvashield range of products is the longest serving embedded galvanic anode for concrete in the world. 14 years of successful projects have been completed with Galvashield anodes. Galvanic systems by their nature have finite life and in temperature climates such as the UK, they are likely to last in the region of 15-20 years. (7) Their holistic use with systems such as car park deck membranes and good quality concrete repair mortars to BS EN1504, mean that corrosion stability can be achieved while aesthetic and safety conditions improvements are made.


CONCLUSION


which are often related to low cover concrete and/or very high chloride concentrations. Once these at risk areas are detected galvanic anodes (Fig 5) can be zoned easily to coincide with the identified areas.


Most manufacturers of decking systems offer 10-year service lives for their products. Most often, high-risk areas for corrosion on a car park are those


Figure 5: The use of zonal embedded galvanic anodes to protect vulnerable areas identified by the use of half-cell mapping


2) 3) 4) 5) 6) 7) 8)


With limited budgets, best value for money is crucial in the maintenance of multi-storey car parks. While ICCP remains the most technically accomplished process and is able to offer life expectancies in excess of 50 years, it is comparatively expensive to apply and requires constant monitoring and upkeep. With owners and engineers experiencing reduced budgets, reduced staffing and expertise in this area, ICCP is becoming less popular and alternative methods are being considered. While galvanic corrosion control has a finite life of between 15-20 years, its performance can be enhanced by the use to car park deck membranes and its use limited to high-risk areas identified by a full half cell survey. The cost of this option can be tailored significantly to reach the budget constraints of the client and meet the target life extension goals of the structure.


*carbonation in car parks is often a contributing factor due to the presence of low concrete cover. Levels of 5mm and less are often seen in the UK.


REFERENCES 1)


‘Recommendations for the inspection, maintenance and management of car park structures’. Institute of Civil Engineers: 2002.


BRE Digest 444 Part 1 ‘Corrosion of steel in concrete - Durability of reinforced concrete structures’. Feb 2000


BRE Digest 444 Part 2 ‘Corrosion of steel in concrete - Investigation and assessment’. Feb 2000


Design Recommendations for multi-storey and underground car parks (fourth edition) The Institute of Structural Engineers: 2011


BRE Digest 491 ‘Corrosion of steel in concrete - a review of the effect of humidity’. 2004


Glass GK, Page CL & Short NR. Factors offering the corrosion rate of steel in carbonated mortars. Corrosion Science (1991), 32 (12), 1283-1294


G. Sergi, D. Simpson, JC Ball. Galvanic anodes for steel reinforced concrete structures. 2011


G. Sergi, AMG Seneviratne, MT Maleki, M. Sadegzadeh. Control of reinforcement corrosion by surface treatment of concrete. Proc, Instn Civ Engrs Structs & Bldgs, 2000, 140, Feb 85-100


subject to the most severe stresses from vehicular traffic. Wear of the decking is also high in these areas and failure may occur before the 10-year period. Once the decking system fails the RH and corrosion activity increases significantly. With the incorporation of galvanic anodes however, this change will be compensated for as those conditions (temperature, moisture etc) that impact corrosion rates, also impact galvanic performance. This additional protection will mean that the concrete substrate for the decking system will remain stable enabling scheduled repair to be made to the coating.


For more information please contact Vector Corrosion - Tel: 01384 671414 or visit the website www.vector-corrosion.eu


VECTOR CORROSION


TEL: 01384 671414


WWW.VECTOR-CORROSION.EU


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