Experimental study of FRP-strengthened concrete beams with corroded reinforcement

Corrosion of steel reinforcement is the major cause of deterioration in reinforced concrete structures. Strengthening of concrete structures has been widely studied. However, most research was conducted on sound structures without considering the effects of corrosion. This paper presents an experimental study of the feasibility of using externally bonded FRP laminates combined with U-jackets, applied directly without repairing the deteriorated concrete cover, to strengthen beams with corroded reinforcement. Ten beams were tested in four-point bending. Two beams were not deteriorated and non-strengthened; these served as references. The other eight were pre-loaded to induce flexural cracks and then exposed to accelerated corrosion. Two of the deteriorated beams were not strengthened, three were strengthened with glass-FRP (GFRP) laminates and three with carbon-FRP (CFRP) plates on the beam soffits. On the six strengthened beams, CFRP U-jackets were installed along the span. Local corrosion levels were evaluated with a 3D-scanning technique. Pitting corrosion significantly reduced the load-carrying and deformation capacity of the deteriorated beams. Despite average corrosion levels of 20%, local corrosion levels up to 57% and corrosion-induced cracks up to 1.9\ua0mm wide, the FRP-strengthening method (applied directly to the beams without repairing the deteriorated concrete cover) was effective in upgrading the load-carrying capacity and flexural stiffness. The applied U-jackets effectively suppressed the delamination of the concrete cover and led to the rupture of GFRP laminates and a utilisation ratio of CFRP plates up to 64%. However, improvement in the deformation capacity was not noticeable; this requires further research

Ta h\ue4nsyn till korrosionsskador vid reparation och f\uf6rst\ue4rkning av betongkonstruktioner!

V\ue5r byggda milj\uf6 best\ue5r till stor del av armerade betongkonstruktioner, varav m\ue5nga har hunnit bli ganska gamla. Till exempel f\uf6rvaltar Trafikverket n\ue4stan 20 000 broar, och merparten \ue4r byggda i armerad betong.Av dessa har m\ue5nga skador i form av korroderad armering. Kommande klimatf\uf6r\ue4ndringar f\uf6rv\ue4ntas \uf6ka p\ue5 skadetakten. F\uf6r broar \uf6kar dessutom kraven p\ue5 lastkapacitet med tiden. Samh\ue4llet st\ue5r d\ue4rf\uf6r inf\uf6r en stor utmaning att kunna garantera s\ue4kerheten i det \ue5ldrande best\ue5ndet med begr\ue4nsade ekonomiska resurser. Att kunna reparera eller f\uf6rst\ue4rka konstruktioner g\uf6r att livsl\ue4ngden f\uf6r m\ue5nga gamla och kulturellt v\ue4rdefulla broar kan f\uf6rl\ue4ngas, vilket ger stora ekonomiska besparingar,minskade koldioxidutsl\ue4pp och mindre st\uf6rningar i trafiken. Vi kommer d\ue4rf\uf6r att i en \uf6kande omfattning beh\uf6va reparera och f\uf6rst\ue4rka konstruktioner med befintliga korrosionsskador. Vi har studerat l\ue4mpliga metoder f\uf6r slakarmerade balkar i ett doktorandprojekt och tv\ue5 examensarbeten p\ue5 Chalmers, se [9], [6], [3]. Resultaten fr\ue5n dessa arbeten presenteras kort i denna artikel