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GFRP Bars in Concrete toward Corrosion-free RC Structures: Bond Behavior, Characterization, and Long-term Durability PredictionYan, Fei January 2016 (has links)
Corrosion of steel reinforcements is the leading causes of malfunction or even failures of reinforced concrete (RC) structures nationwide and worldwide for many decades. This arises up to substantial economic burden on repairs and rehabilitations to maintain and extend their service life of those RC public projects. The inherent natures of glass fiber-reinforced polymers (GFRP) bars, from their superior corrosion resistance to high strength-to-weight ratio, have promoted their acceptance as a viable alternative for steel reinforcement in civil infrastructures. Comprehensive understanding of the bond between GFRP bars and concrete, in particular under in-service conditions or extremely severe events, enables scientists and engineers to provide their proper design, assessment and long-term predictions, and ultimately to implement them toward the corrosion-free concrete products. This research aims to develop a holistic framework through an experimental, analytical and numerical study to gain deep understanding of the bond mechanism, behavior, and its long-term durability under harsh environments. The bond behavior and failure modes of GFRP bar to concrete are investigated through the accelerated aging tests with various environmental conditions, including alkaline and/or saline solutions, freezing-thawing cycles. The damage evolution of the bond is formulated from Damage Mechanics, while detailed procedures using the Arrhenius law and time shift factor approach are developed to predict the long-term bond degradation over time. Besides, the machine learning techniques of the artificial neural network integrated with the genetic algorithm are used for bond strength prediction and anchorage reliability assessment. Clearly, test data allow further calibration and verification of the analytical models and the finite element simulation. Bond damage evolution using the secant modulus of the bond-slip curves could effectively evaluate the interface degradation against slip and further identify critical factors that affect the bond design and assessment under the limit states. Long-term prediction reveals that the moisture content and elevated temperature could impact the material degradation of GFRP bars, thereby affecting their service life. In addition, the new attempt of the Data-to-Information concept using the machine learning techniques could yield valuable insight into the bond strength prediction and anchorage reliability analysis for their applications in RC structures. / ND NASA EPCoR (FAR0023941) / ND NSF EPSCoR (FAR0022364) / US DOT (FAR0025913)
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STRENGTH REDUCTION OF REINFORCED CONCRETE COLUMNS SUBJECTED TO CORROSION RELATED COVER SPALLINGKhalid, Nibras Nizar 23 May 2018 (has links)
No description available.
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Effects of concrete quality and cover depth on carbonation-induced reinforcement corrosion and initiation of concrete cover cracking in reinforced concrete structuresIkotum, Jacob Olumuyiwa January 2017 (has links)
A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy, Johannesburg, 2017 / Many reinforced concrete (RC) structures in inland environment deteriorate early due to carbonation-induced corrosion of their reinforcement. In some cases, the deterioration is visible within a few years of construction in the form of cover concrete cracking. This is widely accepted as one of the limit state indicators in defining the end of functional service life for existing RC structures undergoing corrosion. Many of the currently available service life prediction models are incapable of providing realistic service life estimates of RC structures beyond the corrosion initiation stage. Therefore, the need to incorporate the corrosion initiation and propagation stages in a comprehensive durability prediction approach has been receiving much research attention.
In this research, empirical models were developed for predicting carbonation rate and the amount of steel radius loss required to initiate a first visible crack in concretes exposed to Johannesburg environment. The experimental data for the models were obtained from investigations of carbonation-induced reinforcement corrosion, which were explored in three phases; (i) concrete early-age durability and strength characteristics (ii) carbonation rate of different concrete mixes exposed to the natural inland environment (iii) amount of steel radius loss required to initiate the first visible crack on the pre-carbonated cover concretes exposed to an unsheltered environment. The experimental variables for the earlyage durability and strength tests were; water/binder ratio (w/b) and binder type; w/b, binder type, initial moist curing duration and exposure conditions are the experimental variables for the carbonation rate test. Cover depth, reinforcement diameter, binder type and w/b variables were considered for the corrosion cracking test.
The results showed that an improvement in concrete quality (binder type, w/b ratio and extending the initial moist curing duration) and increment in cover thickness improved the durability of the RC structures exposed to the natural inland environment. Based on the trends in the observed experimental results, models to predict carbonation rate and the amount of steel radius loss required to initiate cover cracking in concrete were developed. The proposed models’ predictions are more closer to the measured values and compared well with the predictions of some previous models which indicate their respective predictive applications. They provide a general basis for durability analysis of RC structures in inland environment and can serve as basis for condition assessment of existing structures in the inland environment. Engineers can appreciate the consequences of design options on the service life of RC structures, while owners of RC structures can have information about how long their RC structures may last before any repair is envisaged / XL2018
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Accelerated curing of concrete with high volume pozzolans - resistivity, diffusivity and compressive strengthUnknown Date (has links)
This investigation presents results of the temperature effect on durability properties (resistivity and diffusivity) and compressive strength of concrete with pozzolans, and the effect of pozzolanic admixtures on microstructure and chemical compositions of concrete pore solution. ... Temperature dependence of electrical resistivity and chloride diffusivity was studied by dynamic temperature tests. Accelerated curing regimes involving curing concrete specimens in 35À C lime water with different durations were tested. Compressive strength test, resisivity measurement and rapid chloride migration (RCM) tests were performed. A leaching method was used to measure pH and conductivity of concrete pore solution. ... The accelerated curing regimes were found to increase the compressive strength and resistance to chloride ion penetration at short-term and long-term. With the developed correlation between resistivity and migration coefficients, it is possible to employ the resistivity measurement as an alternative or replacement of the RCM test to evaluate resistance of chloride ion penetration of concrete. Pozzolanic admixtures were found to decrease both pH and conductivity of concrete pore solution as the replacement ratio increased. Moreover, the migration coefficients were found to be greatly correlated to the microstructure properties of concrete, such as porosity, formation factor and tortuosity. / by Yanbo Liu. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
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Concrete surface resistivity profiles along the splash zone on bridge piles exposed to sea waterUnknown Date (has links)
Prevention of the corrosion of steel reinforcement embedded in concrete is a constant challenge in engineering. A study of concrete surface resistivity versus elevation of partially immersed reinforced concrete structures in a marine splash zone has been developed and correlations made between concrete quality and chloride diffusion, i.e., aggressive ion permeability. A conditioning procedure was developed in which the concrete moisture content is increased by direct contact with fresh water for several days. The electrical resistivity of concrete is known to be primarily a function of the degree of water saturation. Correlations between field obtained concrete surface resistivity values versus chloride diffusivity, and between normalized resistivity measured on cores obtained from the field versus chloride diffusivity has been established. The resistivity values were measured on structures with different concrete mixes and various ages. / by Andres M. Suarez-Solano. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.
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Corrosion Propagation of Rebar Embedded in High Performance ConcreteUnknown Date (has links)
The FDOT has been using supplementary cementitious materials while constructing steel reinforced concrete marine bridge structures for over 3 decades. Previous findings indicated that such additions in concrete mix makes the concrete more durable. To better understand corrosion propagation of rebar in high performance concrete: mature concrete samples that were made (2008/2009) with Portland cement, a binary mix, a ternary mix and recently prepared (April 2016 with 50% OPC + 50% slag and 80% OPC + 20% Fly ash) concrete samples were considered. None of these concretes had any admixed chloride to start with. An accelerated chloride transport process was used to drive chloride ions into the concrete so that chlorides reach and exceed thechloride threshold at the rebar surface and initiate corrosion. Electrochemical measurements were taken at regular intervals (during and after the electro-migration process) to observe the corrosion propagation in each sample. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
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Strength and durability of fly ash-based fiber-reinforced geopolymer concrete in a simulated marine environmentUnknown Date (has links)
This research is aimed at investigating the corrosion durability of polyolefin fiber-reinforced
fly ash-based geopolymer structural concrete (hereafter referred to as GPC, in
contradistinction to unreinforced geopolymer concrete referred to as simply geopolymer
concrete), where cement is completely replaced by fly ash, that is activated by alkalis,
sodium hydroxide and sodium silicate. The durability in a marine environment is tested
through an electrochemical method for accelerated corrosion. The GPC achieved
compressive strengths in excess of 6,000 psi. Fiber reinforced beams contained
polyolefin fibers in the amounts of 0.1%, 0.3%, and 0.5% by volume. After being
subjected to corrosion damage, the GPC beams were analyzed through a method of crack
scoring, steel mass loss, and residual flexural strength testing. Fiber reinforced GPC
beams showed greater resistance to corrosion damage with higher residual flexural
strength. This makes GPC an attractive material for use in submerged marine structures. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2013.
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Diffusion and protection mechanisms of migratory corrosion inhibitors in reinforced concretePhanasgaonkar, Alka, 1956- January 2000 (has links)
Abstract not available
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Shear capacity assessment of corrosion-damaged reinforced concrete beamsFarrow, William C. 19 November 2002 (has links)
The research presented here is a study to determine the effect of shear
reinforcement corrosion on the shear capacity in conventionally reinforced
concrete (CRC) bridge elements. A total of 14 CRC beams were tested using
three stirrup spacings (8, 10, and 12-inch). Six of the beams included the
influence of a 4-inch thick deck, and both positive and negative moment
regions were considered. The CRC beams were subjected to an accelerated
corrosion process to produce the damage states. Inspection techniques were
used to visually correlate corrosion damage with actual structural performance.
Severe corrosion damage was shown to have significant effect on the shear
performance of the CRC beams. Findings indicate that current inspection
ratings for corrosion damage may not adequately identify the extent of
structural deterioration. / Graduation date: 2003
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Unpowered wireless sensors for structural health monitoringAndringa, Matthew 28 August 2008 (has links)
Not available / text
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