The Experts below are selected from a list of 38208 Experts worldwide ranked by ideXlab platform

Mohamed A Sultan - One of the best experts on this subject based on the ideXlab platform.

  • effect of strength and fiber Reinforcement on fire resistance of high strength concrete columns
    Journal of Structural Engineering-asce, 2003
    Co-Authors: Venkatesh Kodur, Fu Ping Cheng, Tien Chih Wang, Mohamed A Sultan
    Abstract:

    In this paper, results from fire resistance experiments on five types of reinforced concrete columns are presented. The variables considered in the study include concrete strength [normal-strength concrete (NSC) and high-strength concrete (HSC)], aggregate type (siliceous and carbonate aggregate), and fiber Reinforcement (Steel and polypropylene fibers). Data from the study is used to determine the structural behavior of HSC columns at elevated temperatures. A comparison is made of the fire resistance performance of HSC columns with that of NSC and fiber-reinforced HSC columns. The factors that influence the thermal and structural behavior of HSC concrete columns under fire conditions are discussed. The results show that the fire resistance of a NSC column is higher than that of a HSC column. Also, the addition of polypropylene fibers and the use of carbonate aggregate improve fire resistance.

Geoffrey Charles Mays - One of the best experts on this subject based on the ideXlab platform.

  • fatigue performance of concrete beams strengthened with cfrp plates
    Journal of Composites for Construction, 2000
    Co-Authors: Richard Andrew Barnes, Geoffrey Charles Mays
    Abstract:

    Recent increases in bridge design loading requirements have highlighted the need for fast, efficient, and durable strengthening methods. External Steel plate bonding provides a satisfactory solution, but carbon fiber reinforced plastic (CFRP) offers the added advantages of resistance to corrosion, low weight, and high mechanical strength. This paper examines the fatigue performance of CFRP-strengthened concrete beams as part of a project investigating the use of CFRP as an alternative to Steel. Five reinforced concrete beams were tested in fatigue: two control beams and three strengthened with externally bonded CFRP plates. Three loading options were used: (1) apply the same loads to both plated and unplated beams, (2) apply loads to give the same stress range in the rebar in both beams, and (3) apply the same percentage of the ultimate load capacity to each beam. Fatigue fracture of the internal Reinforcement Steel would appear to be the dominant factor governing failure, and it would appear reasonable to expect the same fatigue life for plated and unplated beams with comparable values of stress range in the Steel bar.

Donghui Yang - One of the best experts on this subject based on the ideXlab platform.

  • a performance based service life design method for reinforced concrete structures under chloride environment
    Construction and Building Materials, 2016
    Co-Authors: Donghui Yang
    Abstract:

    Abstract The chloride-induced Reinforcement Steel corrosion usually causes premature failure of performance in reinforced concrete structures subjected to chloride environment. However, conventional prescriptive design methods or fully probabilistic methods cannot ensure an explicit performance in design stage. The main objective of this study is to develop a performance-based service life design method, by which concrete structures such as bridges can be designed according to a predefined performance level to satisfy the target service life, reliability and deterioration level. The mechanism of chloride-induced Reinforcement Steel corrosion initiation was analyzed to deduce a time-varying limit state function, and the corresponding stochastic model was developed considering the effects of random factors. Through first-order reliability method, a partial factor formula was deduced to realize performance verification in performance-based design process. Finally, a case study of a concrete bridge deck exposed to marine environment was presented and the sensitivity analysis of Steel corrosion was carried out. The proposed performance-based design method can rationally deal with the uncertainties of random parameters and ensure the predefined target performance to be satisfied during design process instead of predicting performance after design.

Iris De Graeve - One of the best experts on this subject based on the ideXlab platform.

  • inhibitor evaluation in different simulated concrete pore solution for the protection of Steel rebars
    Construction and Building Materials, 2016
    Co-Authors: Hilke Verbruggen, H Terryn, Iris De Graeve
    Abstract:

    Abstract Corrosion of Reinforcement Steel forms a huge problem worldwide. A possible remedy for this problem is the application of corrosion inhibitors. The purpose of this research is to evaluate different inhibitors for both types of corrosion that can occur in reinforced concrete: pitting corrosion (by chloride attack), and uniform corrosion (by a drop in pH). Potentiodynamic polarization measurements in realistic concrete pore solutions (CPS) revealed three critical situations — representing pitting and uniform corrosion, and the combination — in which the inhibitor needs to act. According to polarization experiments and micrographs Na 2 MoO 4 is the best performing inhibitor for the three cases. Our XPS measurements are in line with the proposed inhibitor mechanism by Vukasovich (1986), which is very complex and depends on whether the surface is active or passive to start with. In conclusion Na 2 MoO 4 is a possible — and environmental-friendly — candidate to prevent corrosion of Reinforcement Steel.

O Vennesland - One of the best experts on this subject based on the ideXlab platform.

  • chloride induced Reinforcement corrosion rate limiting step of early pitting corrosion
    Electrochimica Acta, 2011
    Co-Authors: Ueli Angst, Bernhard Elsener, Claus K Larsen, O Vennesland
    Abstract:

    Transition from passive state to stable localised corrosion of Reinforcement Steel in concrete owing to chloride ingress takes place over a period of time rather than being a one-step-occurrence. The depassivation process was characterised by frequent measurements of corrosion potential, polarisation resistance, and macro-cell currents when short-circuiting the working electrode with additional cathode surface. In addition, the concrete resistivity was continuously monitored and cathodic and anodic polarisation curves were measured. The results are consistent and imply that the localised corrosion process is in the initial phase of pit growth under mixed anodic/ohmic control. With time, the anodic reaction kinetics become more limited and the corrosion rate gets almost entirely determined by anodic control. The observed relationship between achieved maximum corrosion current and concrete resistivity indicates that the extent to which the anodic reaction kinetics are restricted is determined by the concrete microstructure and its ability to retain ionic movement.

  • chloride induced Reinforcement corrosion electrochemical monitoring of initiation stage and chloride threshold values
    Corrosion Science, 2011
    Co-Authors: Ueli Angst, Bernhard Elsener, Claus K Larsen, O Vennesland
    Abstract:

    Abstract Reinforcement Steel embedded in six different concrete mixes was exposed to chloride by wetting/drying cycles. Various parameters were continuously monitored during more than 1 year. Cement replacement with fly ash had beneficial long-term effects regarding chloride penetration resistance. Concerning corrosion performance, by far the most dominant influencing parameter was the Steel/concrete interface since corrosion initiated on the lower side of the rebar (with respect to casting direction) regardless of binder type and w/b ratio. In many cases, after the first signs of depassivation, a marked increase in chloride content was required to prevent repassivation and to enable stable pit growth.