The use of fiber-reinforced polymers (FRPs) for the strengthening and repair of existing concrete structures is a field with tremendous potential. The materials are very durable and, hence, ideally suited for use as external reinforcement. Although extensive work has been carried out investigating the use of FRPs for flexural strengthening, a fairly recent development is the use of these materials for the shear strength enhancement of concrete. The current system investigates the use of posttensioned, nonlaminated, carbon fiber-reinforced polymer (CFRP) straps as external shear reinforcement for concrete. Experiments were carried out on an unstrengthened control beam and beams strengthened with external CFRP straps. It was found that the ultimate load capacity of the strengthened beams was significantly higher than that of the control specimen. Existing design codes and analysis methods were found to underestimate the ultimate resistance of the control specimen and the strengthened beams. Nevertheless, th...

Carbonation is a key mechanism for deterioration of reinforced concrete structures. In design for resistance to carbonation, the performance of mixes is often specified and measured in laboratory carbonation tests where initial carbonation is sometimes present in specimens. The coherent interpretation of results from carbonation tests is vital as they enable a more accurate prediction of the performance of concrete structures in situ. This paper assesses two different approaches to considering the initial carbonation depth when extracting the carbonation coefficient from results of carbonation testing. Experimental data is compared to models for either approach using least squares regression. Both linear and non-linear representations of the initial carbonation depth are shown to fit the data well. The non-linear approach gives a larger estimate of carbonation coefficient than the linear approach, and is more consistent with the mathematical derivation of the carbonation equation. The ramifications of this difference will be most significant when the initial carbonation depth is large relative to the depth of the carbonation front. The accurate modelling of carbonation progression underpins performance-based design of new concrete structures and the assessment of existing concrete infrastructure.