Durable design of reinforced concrete elements against corrosion. (15th September 2015) - Ali, M. Shafqat
Highlights: Design for durability of reinforced concrete elements in corrosive environment. Time-dependent correlation between rebar corrosion and its bond strength degradation. Prediction of reduction of ultimate flexural and shear strengths due to corrosion. Double development length needed for durability design at the end of 70 year service life. Decrease in flexural and shear strengths by about 80% and 52%, respectively. Abstract: This paper presents a practice-oriented method for design of flexural concrete members for a given service life in an aggressive environment. A time-dependent correlation between rebar corrosion level in terms of mass loss and its bond strength degradation at the steel–concrete interface, and the ultimate flexural and shear resistances of the reinforced concrete elements is evaluated using basic electrochemistry and empirical relationships. The design development length is determined based on the mass loss prediction and the equation depicting loss of bond strength with mass loss due to corrosion. The results show that the mass loss of rebars depends on several factors, such as the surface chloride concentration, cover thickness to rebar and concrete permeability, rebar size and ratio of the concrete cover thickness to the rebar diameter ( c/db ratio). The model results predict the required development length at the end of the service life of 70 years to be more than twice that obtained from conventional reinforced concrete design. The proposed durability design procedure is illustrated with the help of a detailed design example. Analysis results show that because of corrosion the flexural and shear strengths decrease by about 80% and 52%, respectively, after the service life of 70 years.