The aim of this paper is to explain the chloride concentration profiles obtained experimentally from control\ud samples of an offshore platform after 25 years of service life. The platform is located 12 km off the\ud coast of the Brazilian province Rio Grande do Norte, in the north-east of Brazil. The samples were\ud extracted at different orientations and heights above mean sea level. A simple model based on Fick’s second\ud law is considered and compared with a finite element model which takes into account transport of\ud chloride ions by diffusion and convection. Results show that convective flows significantly affect the\ud studied chloride penetrations. The convection velocity is obtained by fitting the finite element solution\ud to the experimental data and seems to be directly proportional to the height above mean sea level and\ud also seems to depend on the orientation of the face of the platform. This work shows that considering\ud solely diffusion as transport mechanism does not allow a good prediction of the chloride profiles.\ud Accounting for capillary suction due to moisture gradients permits a better interpretation of the material’s\ud behaviour

Spike anchors are a promising way to enhance the maximum capacity and post-peak load-strain response of externally-bonded fibre-reinforced polymer (FRP) materials for retrofitting of concrete structures. Although laboratory testing has proven the effectiveness of these spike anchors (also known as fan anchors), little work has been conducted to provide an analytical basis on which to rely on such anchorage systems. For instance, which parameters govern the behaviour of these anchors? Without an analytical or predictive basis for the behaviour of such anchors, their use will be limited. Therefore, this paper presents an analytical model to be able to predict the behaviour of such anchors, by including important geometrical and installation parameters. This model will, for the first time, allow engineers to specify, with confidence, the use of spike anchors as a method to anchor FRP sheets and plates to structural concrete members

The use of fiber-reinforced polymer (FRP) composites for strengthening, repairing, or rehabilitating concrete structures has become more and more popular in the last 10 years. Irrespective of the type of strengthening used, design is conditioned, among others, by concrete-composite bond failure, normally attributed to stress at the interface between these two materials. Single shear, double shear, and notched beam tests are the bond tests most commonly used by the scientific community to estimate bond strength, effective length, and the bond stress-slip relationship. The present paper discusses the effect of concrete strength and adhesive thickness on the results of beam tests, which reproduce debonding conditions around bending cracks much more accurately. The bond stress-slip relationship was analyzed in a cross section near the inner edge, where stress was observed to concentrate. The ultimate load and the bond stress-slip relationship were\ud visibly affected by concrete strength. Adhesive thickness, in turn, was found to have no significant impact on low-strength concrete but a somewhat greater effect on higher strength materials

Ultra-high-performance concrete (UHPC) is the essential innovation in concrete research of the recent decades. However, because of the high contents of cement and silica fume used, the cost and environmental impact of UHPC is considerably higher than conventional concrete. The use of industrial byproducts as supplementary cementitious materials, in the case of recycled glass powder and fluid catalytic cracking catalyst residue (FCC), the partial substitution of cement and silica fume allows to create a more ecological and cost-efficient UHPC. This research presents a study to determine the possibility of partial substitution of cement by FCC in a previously optimized mixture of ultra-high-performance concrete with recycled glass. The results demonstrate that compressive strength values of 150 and 151 MPa without any heat treatment can be achieved, respectively, when replacing 11% and 15% of the cement with FCC, for a determined amount of water and superplasticizer, compared to 158 MPa obtained for the reference UHPC without any FCC content. The rheology of fresh UHPC is highly decreased by replacing cement particles with FCC.

Ultra-high-performance concrete (UHPC) is a kind of high-tech cementitious material with superb mechanical and durability properties compared to other types of concrete. However, due to the high content of cement and silica fume used, the cost and environmental impact of UHPC is considerably higher than conventional concrete. For this reason, several efforts around the world have been made to develop UHPC with greener and less expensive local pozzolans. This study aimed to design and produce UHPC using local fly ash available in Colombia. A numerical optimization, based on Design of Experiments (DoE) and multi-objective criteria, was performed to obtain a mixture with the proper flow and highest compressive strength, while simultaneously having the minimum content of cement. The results showed that, despite the low quality of local fly ashes in Colombia, compressive strength values of 150 MPa without any heat treatment can be achieved.