The galvanic couple effect decreases a few weeks after performing local repairs. Nonetheless, there is no information on the effect the anodic/cathodic area (aA/aC) ratio has on the magnitude of the galvanic couple. The selective use of stainless steel represents an alternative to repair of concrete structures, but it remains understudied, particularly in the tropical marine environments of the Gulf of Mexico. In this paper, we analyze and discuss the infl uence of the anodic/cathodic area ratio on the galvanic behavior of local repairs conducted on small beams made of low-quality concrete and 304 stainless steel (SS) bars. Results from this experiment indicate that an aA/aC ratio of more than 5 causes a signifi cant decrease in the galvanic couple of the adjacent areas.

Due to the different characteristics of higher strength concrete, some procedures traditionally used in the design of structures made of lower-strength concrete have to be changed. To evaluate the behavior of high-strength concrete (HSC) elements (fc > 50 MPa) with reasonable accuracy, an adequate compressive stress-strain relationship of concrete should be adopted. This is particularly important for predicting the behavior of columns - elements where the use of HSC is most advantageous. Different types of stress-strain relationships for HSC have been proposed for the nonlinear analysis of member behavior and for the ultimate state analysis of cross sections of elements under combined fl exure and axial load. In this work, simplifi ed rectangular stress blocks for the design of cross sections by different codes applicable to HSC structures are presented. It is shown that those concrete stress blocks can lead to quite different bending moment-axial load interaction diagrams and comparisons between experimental and calculated strengths of 403 tested columns give an idea of the level of safety related to the use of various concrete stress blocks.

This paper presents a comparative analysis of the predicted shear capacities of beams obtained by using several design criteria with respect to test results of reinforced concrete beams built with high-performance concrete (fc > 50 Mpa). The database contains a total of 234 test beams with and without web reinforcement. The employed design criteria are EUROCODE 2 and the simplified methods of ACI 318 and Canadian CSA A23.3. The Brazilian code (NBR 6118) procedures and Zsutty’s method are also included in the study. Statistics of the ratio of test-to-predicted shear capacity are used to evaluate the adequacy of these design models in terms of safety, precision, and economy. The effects of the depth of the beams, concrete compressive strength, and the amount of longitudinal and web reinforcement are also investigated. The results show that for the beams without web reinforcement, EUROCODE 2, and Zsutty’s method are the most suitable procedures; NBR 6118 provisions, on the other hand, need adjustments because they can have inadequate margins of safety. The performance of the shear predicting models of ACI 318, the CSA A23.3 and NBR 6118 (? = 45°) for beams with web reinforcement are similar but significantly biased; EUROCODE 2, in this case, is extremely conservative and consequently not economical. Overall, Zsutty’s method was the best predicting model among those included in this study.

A previous research presented a model to forecast chloride ion penetration over time in samples where chloride profiles form a peak, i.e. the concentration of chloride ions first increases as we move from the surface to the interior of the structure and then show a decrease after a specific depth. This study presents the variation of this profile over time through measurements at different ages and compares these results with the values forecast by the model of Guimarães and Helene using the first profile measured in the structure. The model showed good accuracy in this case study and should be confirmed in other structures in use.

The heat of hydration in massive concrete structures can raise the temperature to a level where thermal cracks can pose a problem. Hardening retarders are admixtures that lower the rate of hydration, distribute the heat release over time, and lower maximum temperature in concrete. Such admixtures will inherently lead to lower early strength, but should lead to comparable 28-day strength to reference concrete. Relative large amounts of urea works, in particular when the additional retardation of setting (not hardening) is counteracted by the set accelerator calcium nitrate. However, these dosages are high, and urea will also slowly decompose to ammonia that may limit the urea application to outdoor use, if any. The latest potential admixtures are combinations of minor amounts of strong setting retarders like organic acids (0.1-0.3 %) with the setting accelerator calcium nitrate (1-3%), where a true synergy between the two leads to hardening retardation.