Concrete technology and durability design - Cowi

12Special design solutionsWaterproofing membrane installed inbored tunnel, Hallandsås Tunnel, SwedenSelective use of stainless steel reinforcement,Stonecutters Bridge, Hong Kong, ChinaSelective use of stainless steel reinforcement,Sheikh Zayed Bridge, Abu DhabiPhotomontage: HPRMembranesThe application of membranes forconcrete structures can be twofold:either to achieve a watertight concretestructure or to act as a protectivebarrier in case of concrete attack,e.g. high sulphate concentrationsin soil/groundwater.COWI has specialist experienceand can support clients and contractorswith selecting the most appropriatemembrane type depending onthe aggressivity of the environment,the geometric conditions of thestructure and the construction procedure.Diaphragm walls and secantpilesHistorically, diaphragm walls andsecant piles have been used withsuccess in relatively benign environments.However, in more hostile oraggressive environments, e.g. in theMiddle East, and with extendedservice life expectancy, special measuresare necessary to secure the requireddurability of the structure.COWI has specialist experience inthis area and can support clientsand contractors by providing innovativedurability design solutions, asspecial reinforcement solutions and/or concrete mix-design requirementsto mitigate the effects of chlorideinduced reinforcement corrosion.Corrosion resistantreinforcementThe implementation of corrosionresistant steel reinforcement is thesimplest and most effective methodto eliminate the risk of reinforcementcorrosion. This method doesnot only solve the corrosion problemin an infallible way even in themost corrosive chloride environments,but it also leaves the siteactivities nearly unchanged. Theselective use of stainless steel reinforcementin zones exposed to highchloride concentrations is a highlyreliable solution. This solution ensuresvery long problem-free servicelife in that part of the structure, providedthe concrete itself is made sufficientlyresistant to avoid othertypes of deterioration. Of particularimportance is the often overlookedfact, that SSR can be coupled withcarbon steel reinforcement withoutcausing galvanic corrosion. Anotherbenefit is the added value, whichfollows from the possibility of acceptingthe use of locally availablematerials even with chloride contaminationand the possible lack ofspecial qualifications of the localwork force.COWI has expert knowledge inspecifying appropriate reinforcementsolutions to attain the requiredservice life in all possible environments.COWI’s durability specialists canalso offer services concerning theassessment of alternative corrosioncountermeasures for concrete reinforcementand for the evaluation ofcorrosion protection of exposedstructural steel. This is supported bya continuous cooperation with universitiesand COWI’s involvement invarious related ongoing and futureR&D projects.Testing of reinforcementcorrosion countermeasures