Current Search: info:fedora/fau:CurrentETDs (x) » Almost a woman. (x) » Hartt, William H. (x)
View All Items
Pages
- Title
- Effects of High Alkalinity Cements on the Control of Alkali-Silica Reaction for Reinforced Concrete.
- Creator
- Suarez, Jorge Alejandro, Hartt, William H., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
In previous research, cements with high alkali content (EqA 1.0-1.2 percent) extended the corrosion initiation time of reinforcing steel in concrete. During this study, laboratory tests were performed to determine the suitability of high alkalinity cements to improve concrete durability without modifying physical properties and to control the risk of alkali-aggregate reaction (AAR). A mix design for the FOOT-Class V concrete served as base material for this study. On a cubic meter basis the...
Show moreIn previous research, cements with high alkali content (EqA 1.0-1.2 percent) extended the corrosion initiation time of reinforcing steel in concrete. During this study, laboratory tests were performed to determine the suitability of high alkalinity cements to improve concrete durability without modifying physical properties and to control the risk of alkali-aggregate reaction (AAR). A mix design for the FOOT-Class V concrete served as base material for this study. On a cubic meter basis the cementitious material in this concrete included 363 kg of Type l/ll Portland cement and 83 kg of Class F fly ash. The water-to-cementitious material ratio of the concrete was 0.40. The fine aggregate used in the experimental concretes was quartz sand from a Florida source with no history of alkali-silica reactivity (ASR) susceptibility. A number of cement alkali contents were prepared by different additions of sodium hydroxide to the concrete mix (3.42 - 4.57 kglm\ in some cases, and by using different cements in others. Thus, effects on concrete susceptibility to ASR, electrical resistivity, and strength were studied. Pore water alkalinity was measured by ex-situ leaching and pore water extraction methods. It was concluded that leaching procedures were not appropriate to determine concrete pore water alkalinity in the presence of fly ash. Results suggested that it is feasible to use high alkali cement without the risk of ASR or the loss of strength for two of the seven coarse aggregates studied, given that supplementary cementitious materials and lithium nitrate admixtures are utilized. Criteria for qualification of a concrete as being ASR resistant was based on dimensional stability (less than 0.01% average specimen length change) and the absence of cracking over the one and two year exposure periods according to ASTM Cl293. Based on the fundamentals of the electric double layer theory, the incidence of bivalent cations adjacent to the surface of cement hydrates and reactive silica particles was proposed to provide an explanation for the effects of alkali addition on the electrical resistivity of concrete and the source of the expansive nature of the ASR gel.
Show less - Date Issued
- 2006
- PURL
- http://purl.flvc.org/fau/fd/FA00012578
- Subject Headings
- Reinforced con crete construction, Concrete--Deterioration, Alkali-aggregate reactions, Silica
- Format
- Document (PDF)
- Title
- Experimental and Modeling Study of Chloride Ingress into Concrete and Reinforcement Corrosion Initiation.
- Creator
- Yu, Hui, Hartt, William H., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Effects of reinforcement and coarse aggregate on chloride ingression into concrete and reinforcement corrosion initiation have been studied with experimental and modeling (finite element method) analyses. Once specimens were fabricated and exposed to a chloride solution, various experimental techniques were employed to determine the effect of reinforcement and coarse aggregate on time-to-corrosion and chloride ingress and concentration at corrosion locations. Model analyses were performed to...
Show moreEffects of reinforcement and coarse aggregate on chloride ingression into concrete and reinforcement corrosion initiation have been studied with experimental and modeling (finite element method) analyses. Once specimens were fabricated and exposed to a chloride solution, various experimental techniques were employed to determine the effect of reinforcement and coarse aggregate on time-to-corrosion and chloride ingress and concentration at corrosion locations. Model analyses were performed to verify and explain the experimental results. Based upon the results, it was determined that unexpectedly higher chloride concentrations were present on the top of the rebar trace than that to the side at the same depth and an inverse concentration gradient (increasing [Cl-] with increasing depth) occurred near the top of rebars. Also, coarse aggregate volume profile in close proximity to the rebar and spatial distribution of these aggregates, in conjunction with the physical obstruction afforded by reinforcement to chloride flow, complicates concrete sampling for Cl- intended to define the critical concentration of this species to initiate corrosion. Modeling analyses that considered cover thickness, chloride threshold concentration, reinforcement size and shape, and coarse aggregate type and percolation confirmed the experimental findings. The results, at least in part, account for the relatively wide spread in chloride corrosion threshold values reported in the literature and illustrate that more consistent chloride threshold concentrations can be acquired from mortar or paste specimens than from concrete ones.
Show less - Date Issued
- 2007
- PURL
- http://purl.flvc.org/fau/fd/FA00012582
- Subject Headings
- Reinforced concrete construction--Corrosion, Chlorides--Diffusion rate, Composite reinforced concrete, Concrete--Chemical resistance
- Format
- Document (PDF)
- Title
- Effect of Polarization on Steel Embedded in Simulated Piling Specimens Evaluated by Critical Chloride Threshold.
- Creator
- Tanner, Russell, Hartt, William H., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Critical chloride threshold, CT values for initiation of reinforced steel corrosion m mortar typical of Florida coastal bridge substructures were determined in laboratory tests. Previous research has reported CT values that vary by more than an order-of-magnitude, making design life estimation for structures difficult. On this basis, experiments on piling type specimens focused on [Cl-] contamination in the splash zone and coupling of this steel to a large surface area submerged anode. The...
Show moreCritical chloride threshold, CT values for initiation of reinforced steel corrosion m mortar typical of Florida coastal bridge substructures were determined in laboratory tests. Previous research has reported CT values that vary by more than an order-of-magnitude, making design life estimation for structures difficult. On this basis, experiments on piling type specimens focused on [Cl-] contamination in the splash zone and coupling of this steel to a large surface area submerged anode. The lower portion of simulated piling was immersed and the region above the waterline periodically sprayed with NaCI solution. Corrosion potential with respect to height above the waterline was monitored. A temporary depolarization method for determining as to whether or not corrosion had initiated is proposed. Chloride distribution at the reinforcement-concrete interface was determined in piling using energy dispersive x-ray analysis and related to height with respect to the waterline. Chloride threshold was related to corrosion potential.
Show less - Date Issued
- 2007
- PURL
- http://purl.flvc.org/fau/fd/FA00012560
- Subject Headings
- Reinforced concrete construction, Steel, Structural--Corrosion, Chlorides, Corrosion and anti-corrosives, Seawater corrosion
- Format
- Document (PDF)
- Title
- Evaluation of Corrosion Resistant Ferric-Alloys in Chloride Contaminated Concrete.
- Creator
- Himiob, Rodrigo J., Hartt, William H., Florida Atlantic University
- Abstract/Description
-
The penetration of chloride ions through concrete can compromise the integrity of a structure. The chloride concentration, [Cl-], at which the corrosion process initiates is termed the critical chloride concentration or chloride threshold, [Cl-]th. One of the purposes of this research was to determine the [Cl-]th for various reinforcing alloys. Furthermore, the time-to-corrosion (TIC) was measured to determine the time at which bars become active. Both parameters, [Cl-]th and TTC, were found...
Show moreThe penetration of chloride ions through concrete can compromise the integrity of a structure. The chloride concentration, [Cl-], at which the corrosion process initiates is termed the critical chloride concentration or chloride threshold, [Cl-]th. One of the purposes of this research was to determine the [Cl-]th for various reinforcing alloys. Furthermore, the time-to-corrosion (TIC) was measured to determine the time at which bars become active. Both parameters, [Cl-]th and TTC, were found to be distributed; therefore, statistical analyses were performed to forecast the probability of activity. A new experimental procedure was introduced to increase the TTC data set by electrically isolating the top bars as they became active. The research also compared the [Cl-] for core samples with those values obtained from along the top rebar trace. In general, this analysis demonstrated that core sample [Cr] was lower than at the rebar-trace.
Show less - Date Issued
- 2007
- PURL
- http://purl.flvc.org/fau/fd/FA00012527
- Subject Headings
- Steel--Corrosion, Reinforcing bars--Corrosion, Chlorides
- Format
- Document (PDF)
- Title
- Spectrum fatigue of welded structural steel in sea water.
- Creator
- Clark, A. M., Qian, D., Hartt, William H., Martin, P. E., Czarnecki, M. F., Harbor Branch Oceanographic Institute
- Date Issued
- 1983
- PURL
- http://purl.flvc.org/fau/fd/FA00007432
- Subject Headings
- Offshore structures--Welded joints--Fatigue, Steel, Structural--Fatigue, Seawater
- Format
- Document (PDF)
- Title
- Fatigue crack growth rate of short cracks for high strength steels in sea water.
- Creator
- Kim, Kijoon., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Experiments have been performed which determined the fatigue crack growth rate (FCGR) of short cracks (a > 0.1mm) for five high strength steels (yield stress 370-570 MPa) in air and in natural seawater with and without cathodic protection. Attention was focused upon Regions I and Il of the classical FCGR-stress intensity range(Delta K) curve with particular consideration of the near-threshold behavior for short cracks. Single edge notch (SEN) three-point bend specimens and a direct current...
Show moreExperiments have been performed which determined the fatigue crack growth rate (FCGR) of short cracks (a > 0.1mm) for five high strength steels (yield stress 370-570 MPa) in air and in natural seawater with and without cathodic protection. Attention was focused upon Regions I and Il of the classical FCGR-stress intensity range(Delta K) curve with particular consideration of the near-threshold behavior for short cracks. Single edge notch (SEN) three-point bend specimens and a direct current potential drop (DCPD) crack monitoring system were employed, and test parameters simulated offshore structure conditions. The results indicated enhanced FCGR for short cracks compared to macrocracks by 3-20 times in air and 2-6 in seawater free-corroding(FC). Also, the Delta Kth for short cracks was apparently lower than for long ones in both environments. The transition from short to long crack behavior occurred at constant $\Delta$K in each environment (15.6 MPa m in air and 10.0 MPa m in seawater(FC)) irrespective of initial Delta K (Delta K(0)). The transition crack length ranged from 0.25 to 1.6 mm and was inversely proportional to $\Delta$K(0). Scanning electron microscope fractography showed that the mechanism of enhanced crack growth rate was associated with secondary crack (SC) formation in air and SC or inter-granular cracking (or both) in seawater (FC). The enhanced FCGR for short cracks was minimized by polarization to -950 mV(SCE). Through an elastic-plastic fracture mechanics analysis using the J-integral parameter it was found that the influence of plastic deformation at the crack tip was approximately independent of crack length (short versus long), and the linear-elastic fracture mechanics analysis gave a realistic representation for fatigue behavior.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/12313
- Subject Headings
- Steel--Fatigue--Environmental aspects, Underwater acoustics, Seawater--Acoustic properties
- Format
- Document (PDF)
- Title
- Characterization of electrochemical properties of arc-sprayed zinc and zinc-aluminum alloy coatings for cathodic protection of reinforced concrete structures.
- Creator
- Sigonney, Yann Manuel., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The present research focused on the behavior of arc sprayed zinc and zinc-aluminum coatings on concrete specimens exposed to specific relative humidity environments (100, 85, 60 and 25% RH) and with specific chloride contents (0.0, 3.0, 5.9 and 11.8 kg/m^3). All specimens experienced a decline in current output with time. Anode wastage and formation of oxidation products were mainly responsible for this lack of protection in 100 and 85% RH, whereas for 60 and 25% RH, drying of the concrete...
Show moreThe present research focused on the behavior of arc sprayed zinc and zinc-aluminum coatings on concrete specimens exposed to specific relative humidity environments (100, 85, 60 and 25% RH) and with specific chloride contents (0.0, 3.0, 5.9 and 11.8 kg/m^3). All specimens experienced a decline in current output with time. Anode wastage and formation of oxidation products were mainly responsible for this lack of protection in 100 and 85% RH, whereas for 60 and 25% RH, drying of the concrete and long-term polarization of the anode were the key factors. Validity of the DC measurements was verified with slope parameter analysis on selected specimens. In addition, Electrochemical Impedance Spectroscopy was performed on the galvanic anode and an equivalent circuit model was obtained for the zinc-concrete interface.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15665
- Subject Headings
- Reinforced concrete--Corrosion, Cathodic protection, Zinc coating
- Format
- Document (PDF)
- Title
- Influence of pozzolanic admixtures on concrete pore water pH, chloride diffusion and chloride binding.
- Creator
- Charvin, Stephanie., Florida Atlantic University, Hartt, William H.
- Abstract/Description
-
This report describes the results obtained from reinforced concrete slabs having different fly ash and silica fume content. The specimens are submitted to periodic seawater ponding. PH measurements as well as free and total chloride analyses were achieved at 1213 days in order to study the alkalinity, resistance to chloride ingress and binding properties afforded by each mix design. Water absorption experiments were also conducted at different relative humidities and in water. Pore water pH...
Show moreThis report describes the results obtained from reinforced concrete slabs having different fly ash and silica fume content. The specimens are submitted to periodic seawater ponding. PH measurements as well as free and total chloride analyses were achieved at 1213 days in order to study the alkalinity, resistance to chloride ingress and binding properties afforded by each mix design. Water absorption experiments were also conducted at different relative humidities and in water. Pore water pH was found to decrease with increasing admixture content and increasing relative humidity. The permeability to chloride ions was significantly reduced in the fly ash blends whereas most of the silica fume blends exhibited effective diffusion coefficients and chloride concentrations at the depth of steel marginally better than the controls. Both the fly ash and silica fume blends showed similar binding capacity at a given replacement ratio, the percentage of bound chloride increasing with increasing admixture content.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15664
- Subject Headings
- Reinforced concrete construction--Corrosion, Concrete--Additives
- Format
- Document (PDF)
- Title
- Galvanic anode cathodic protection (CP) retrofit upon offshore pipelines: An analytical model for CP potential profiles.
- Creator
- Pierson, Patrick Robert., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
An analytical model for cathodic protection (CP) attenuation along a one-dimensional structure such as a pipeline is developed in terms of non-dimensional polarization and, alternately, cathode potential. The derivation is based upon the fundamental principle that (1) potential is, in fact, the potential difference across the metal/electrolyte interface, (2) an assumption of a linear potential and current density relationship, and (3) the treatment of Galvanic anodes as spherical current...
Show moreAn analytical model for cathodic protection (CP) attenuation along a one-dimensional structure such as a pipeline is developed in terms of non-dimensional polarization and, alternately, cathode potential. The derivation is based upon the fundamental principle that (1) potential is, in fact, the potential difference across the metal/electrolyte interface, (2) an assumption of a linear potential and current density relationship, and (3) the treatment of Galvanic anodes as spherical current sources. The resulting expression characterizes the distribution of protection in terms of physical design variables and electrochemical properties of the cathode. Polarization is presented graphically in terms of two parameters which are comprised of the aforementioned variables and make for a novel method of analysis. Two sample pipeline CP systems are analyzed by this method, one of which is an existing design and the other a hypothetical design used to illustrate the effect of the varying parameters. Some sample anode life calculations based upon the analytical model are performed, and a method for correcting the model for the existence of a non-spherical bracelet anode is proposed. It is concluded that electrolyte resistance (or alternately anode resistance) is of greater importance in all practical Galvanic CP attenuation calculations than is the metallic (Ohmic) resistance.
Show less - Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/15581
- Subject Headings
- Petroleum pipelines--Cathodic protection, Natural gas pipelines--Cathodic protection
- Format
- Document (PDF)
- Title
- Non-destructive evaluation of corrosion-damaged pre-stressing steel in jacketed concrete piles.
- Creator
- Rapa, Martin Tymon., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A study was performed for the purpose of developing a non-destructive method to evaluate corrosion damaged pre-stressing steel in jacketed concrete piles by using a cover meter. The procedure first involved taking cover meter readings with the pile jacket in place. Subsequently, a portion of the jacket was removed and tendon diameter measurements were taken. A relation for normalized tendon diameter as a function of normalized cover was determined, where normalized cover increased with a...
Show moreA study was performed for the purpose of developing a non-destructive method to evaluate corrosion damaged pre-stressing steel in jacketed concrete piles by using a cover meter. The procedure first involved taking cover meter readings with the pile jacket in place. Subsequently, a portion of the jacket was removed and tendon diameter measurements were taken. A relation for normalized tendon diameter as a function of normalized cover was determined, where normalized cover increased with a decrease in normalized tendon diameter. Finally, it is projected that the cover meter is a useful non-destructive tool to estimate the remaining tendon diameter in the inspection of jacketed, prestressed concrete piles and to this end to characterize the residual structural integrity of piles.
Show less - Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/15563
- Subject Headings
- Concrete piling, Prestressed concrete constuction--Corrosion, Prestressed steel constuction--Corrosion
- Format
- Document (PDF)
- Title
- The assessment of bond for cathodically polarized pretensioning steel in concrete.
- Creator
- Dohlen, Knut Herman., Florida Atlantic University, Hartt, William H.
- Abstract/Description
-
Pretensioned concrete members require a certain bond strength between the steel and concrete to maintain prestress force. Previous studies have indicated that when reinforcing steel in concrete is cathodically polarized, a chemical change of the cement near the steel-concrete interface occurs; and this can reduce the bond strength. In the present research experiments were conducted with concrete specimens that contained either a non-stressed seven wire steel tendon or a single strand through...
Show morePretensioned concrete members require a certain bond strength between the steel and concrete to maintain prestress force. Previous studies have indicated that when reinforcing steel in concrete is cathodically polarized, a chemical change of the cement near the steel-concrete interface occurs; and this can reduce the bond strength. In the present research experiments were conducted with concrete specimens that contained either a non-stressed seven wire steel tendon or a single strand through the longitudinal direction. The specimens were cathodically polarized with current densities ranging between 50 and 2500 mA/m^2 of steel. Upon achieving a pre-determined charge density transfer, the steel was pulled relative to the concrete until the bond was broken. Results indicate that a total charge density transfer of up to 14000 A*h/m^2 of steel, may introduce an average 16 percent decrease in ultimate bond strength. This and other data were evaluated in order to assess if cathodic protection, as utilized for corrosion control, is likely to compromise structural integrity of pretensioned concrete members and structures.
Show less - Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/15543
- Subject Headings
- Cathodic protection, Reinforced concrete--Corrosion
- Format
- Document (PDF)
- Title
- Evaluation of carbon fiber/polyetheretherketone composites exposed to marine microbial communities in laboratory media and natural seawater.
- Creator
- Sheetz, Andrew Douglas., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This research proposed to characterize any microbial induced degradation of carbon fiber/polyetheretherketone (PEEK) composites from acid-producing bacteria (APB) and sulfate-reducing bacteria (SRB). Electrochemical impedance spectroscopy (EIS) was used to provide a measure of degradation of the composite system as a function of exposure time. In addition, mechanical testing and microscopic evaluation of the specimens were utilized to determine if changes in the EIS spectra as a function of...
Show moreThis research proposed to characterize any microbial induced degradation of carbon fiber/polyetheretherketone (PEEK) composites from acid-producing bacteria (APB) and sulfate-reducing bacteria (SRB). Electrochemical impedance spectroscopy (EIS) was used to provide a measure of degradation of the composite system as a function of exposure time. In addition, mechanical testing and microscopic evaluation of the specimens were utilized to determine if changes in the EIS spectra as a function of exposure time correlated to changes in the mechanical properties. Results from most EIS scans were consistent with a well-consolidated and undamaged composite system. Changes in the EIS response of specimens exposed to the SRB environment were not matched by a reduction in the flexural strength. Mechanical testing also indicated no reduction in the flexural strength in any of the other exposure environments. Environmental scanning electron microscopy (ESEM)/energy dispersive x-ray spectroscopy (EDS) were inconclusive, though changes in the EDS spectra were seen. No definitive degradation was seen to occur in this composite system.
Show less - Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/15531
- Subject Headings
- Corrosion and anti-corrosives, Composite materials--Biodegradation
- Format
- Document (PDF)
- Title
- A critical evaluation of current demand determination methods for cathodic protection retrofits of offshore structures.
- Creator
- Lemieux, Edward John., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Development of a baseline design protocol for cathodic protection retrofits of offshore structures is becoming an increasingly important topic in light of the large number of structures operating beyond their original cp system design life. One of the critical steps in this development is determination of the total anode mass which is required to continue sufficient cathodic protection for which structure current demand must be established. Three current demand determination methods were...
Show moreDevelopment of a baseline design protocol for cathodic protection retrofits of offshore structures is becoming an increasingly important topic in light of the large number of structures operating beyond their original cp system design life. One of the critical steps in this development is determination of the total anode mass which is required to continue sufficient cathodic protection for which structure current demand must be established. Three current demand determination methods were investigated including the Gaussian ammeter, the Potential method, which utilizes the driving potential and anode resistance in its current calculation, and the IR Drop method. To this end, three anodes were deployed at the Naval Research Laboratory, Key West, Fl., and current output determinations were made upon these. Each of the three current measurement methods was evaluated on the basis of accuracy, reliability and feasibility in field use.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15503
- Subject Headings
- Cathodic protection, Offshore structures, Ocean currents
- Format
- Document (PDF)
- Title
- Cathodic polarization behavior of mild steel exposed to selected flow velocities and slope parameters in natural seawater.
- Creator
- Hugus, G. Dickson, IV., Florida Atlantic University, Hartt, William H.
- Abstract/Description
-
Twenty-four test cells arranged in a pipe flow setup were assembled to investigate the effect of seawater velocity on the polarization behavior of galvanically polarized mild steel. Each 1023 steel pipe specimen of 10.8 em ID was coupled via a current limiting resistor to a mercury activated aluminum anode and exposed to a velocity of either 0.03, 0.09 or 0.30 m/s. The resistors were sized such that polarization was controlled according to one of six slope parameters. Steady state potential...
Show moreTwenty-four test cells arranged in a pipe flow setup were assembled to investigate the effect of seawater velocity on the polarization behavior of galvanically polarized mild steel. Each 1023 steel pipe specimen of 10.8 em ID was coupled via a current limiting resistor to a mercury activated aluminum anode and exposed to a velocity of either 0.03, 0.09 or 0.30 m/s. The resistors were sized such that polarization was controlled according to one of six slope parameters. Steady state potential and maintenance current density values were determined, and a steady state potential vs. current density curve was established for specimens in each velocity. Some specimens experienced a rise in cathode potential and current density after an apparent steady state had been reached. This was probably related to the influence of velocity on the protectiveness of the calcareous deposit. Of the specimens that experienced a rise in steady state potential and current density, a few were later observed to decrease in potential and current density and reach steady state. Steady state current density vs. velocity plots of specimens at steady state potentials of -0.78, -0.88 and -0.98 V showed that current density was directly proportional to velocity as well as relatively insensitive to potential. Ficks' first law was utilized in conjunction with an empirically derived dimensionless correlation that characterizes the behavior between fluid velocity and mass transfer of molecular species from the bulk solution to the cathode surface in turbulent seawater pipe flow. Calcareous deposit porosity constants were calculated and it was surmised that as velocity increased by a factor of three, the porosity of the deposits near 0.78 and -0.89 V increased by multiples of about two on average. Porosity at the above potentials increased with decreasing potential by a factor of a little over two. SEM micrographs were made and EDX analyses were performed on the calcareous deposits of selected specimens.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15501
- Subject Headings
- Cathodic protection, Seawater corrosion, Marine steel
- Format
- Document (PDF)
- Title
- Brittle propensity of chromium microalloyed and corroded prestressing steel under cathodic protection.
- Creator
- Stauder, Anne-Laure T., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Qualification criteria for cathodic protection of pre-tensioned tendon wires in concrete were studied with regard to the risks of embrittlement due to chromium microalloying and existing corrosion damage. The selected materials included two microalloyed (with 0.23 and 0.24 w% chromium) and one non-microalloyed, high carbon prestressing steels. The slow strain rate testing technique was used to evaluate the effects of polarization to -0.90 and -1.30 VSCE upon strength and ductility of the...
Show moreQualification criteria for cathodic protection of pre-tensioned tendon wires in concrete were studied with regard to the risks of embrittlement due to chromium microalloying and existing corrosion damage. The selected materials included two microalloyed (with 0.23 and 0.24 w% chromium) and one non-microalloyed, high carbon prestressing steels. The slow strain rate testing technique was used to evaluate the effects of polarization to -0.90 and -1.30 VSCE upon strength and ductility of the steels. Fractographic analysis was performed using scanning electron microscopy. Based upon statistical analysis, an attempt was made to relate the remaining strength of the corroded wire to the extent of corrosion damage for different corrosion morphologies.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15475
- Subject Headings
- Cathodic protection, Tendons (Prestressed concrete), Steel--Corrosion, Steel--Embrittlement
- Format
- Document (PDF)
- Title
- Embrittlement susceptibility of corroded pre-stressing steel in concrete during cathodic polarization.
- Creator
- Poeydomenge, Arnaud., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Experiments and analyses were performed to better define the limits of concern regarding hydrogen embrittlement in association with application of cathodic protection to prestressed concrete. To accomplish this, prestressed concrete specimens were locally corroded to different levels by anodic polarization and then polarized to -1.30 V SCE. A procedure of examination was developed using strain gauges to determine the level of prestrain. Relatively few brittle failures of wires resulted due,...
Show moreExperiments and analyses were performed to better define the limits of concern regarding hydrogen embrittlement in association with application of cathodic protection to prestressed concrete. To accomplish this, prestressed concrete specimens were locally corroded to different levels by anodic polarization and then polarized to -1.30 V SCE. A procedure of examination was developed using strain gauges to determine the level of prestrain. Relatively few brittle failures of wires resulted due, at least in part, to a relatively low prestrain of the pretensioned tendons. A model was developed which, coupled with data from parallel research, permitted definition of the minimum cross section for brittle failure as a function of the magnitude of prestrain and corrosion morphology of the wire. These results were tabulated in a format that can be used during field inspection to identify structural elements for which fracture could occur upon application of cathodic protection.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15417
- Subject Headings
- Prestressed concrete--Corrosion, Cathodic protection, Prestressed concrete--Embrittlement, Prestressed steel construction
- Format
- Document (PDF)
- Title
- pH determination of concrete pore water by a leaching technique for various concrete mixtures.
- Creator
- Sitton, Izic., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A pH determination technique of concrete pore water by means of leaching OH- ions from powdered samples was developed. This method was then evaluated in terms of sample size, extent of dilution, leaching period, the type of leaching, calcium hydroxide error, and titration scatter. Based upon variations of the above parameters it was concluded that a maximum amount of hydroxide ions was released into solution for samples with the smallest particle size within a 24 hours static leaching period....
Show moreA pH determination technique of concrete pore water by means of leaching OH- ions from powdered samples was developed. This method was then evaluated in terms of sample size, extent of dilution, leaching period, the type of leaching, calcium hydroxide error, and titration scatter. Based upon variations of the above parameters it was concluded that a maximum amount of hydroxide ions was released into solution for samples with the smallest particle size within a 24 hours static leaching period. A 50ml dilution volume proved optimum with regard to filtration and titration. Under the above circumstances calcium hydroxide dissolution did not seem to pose a significant source of error. Furthermore, repeatability of the measurements was good and titration scatter was determined to be about 0.05 pH units. This method was used to determine the pH of samples containing different amounts of fly ash or silica fume additions as well as plain cement (control) samples. A drop in OH- concentration, that is pH, was detected with increasing pozzolanic addition. The results are discussed with the context of the degree of corrosion mitigation afforded by these pozzolans.
Show less - Date Issued
- 1996
- PURL
- http://purl.flvc.org/fcla/dt/15364
- Subject Headings
- Concrete--Corrosion, Seawater corrosion, Concrete--Testing, Leaching
- Format
- Document (PDF)
- Title
- Influence of direct electrical current upon specific volume of mortar in sea water.
- Creator
- Le Floch, Anne., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Hollow, cylindrical mortar specimens of 0.4 water-cement ratio were prepared without reinforcement and exposed to flowing natural sea water for periods up to one year. Direct currents of 2, 10 and 50 mA were impressed between a mixed metal-oxide titanium substrate electrode positioned within each of these two zones, with a different electrolyte supply and exhaust for the cylinder core and exterior surface. Linear expansion of the specimens was evaluated as a function of exposure duration from...
Show moreHollow, cylindrical mortar specimens of 0.4 water-cement ratio were prepared without reinforcement and exposed to flowing natural sea water for periods up to one year. Direct currents of 2, 10 and 50 mA were impressed between a mixed metal-oxide titanium substrate electrode positioned within each of these two zones, with a different electrolyte supply and exhaust for the cylinder core and exterior surface. Linear expansion of the specimens was evaluated as a function of exposure duration from the output of embedded strain gages and from dimensional measurement of cylinder length and diameter. It was found that expansion of specimens exposed to direct current exceeded baseline ones (no current). Also, the expansion was anisotropic in that different magnitudes and trends were apparent for the diameter versus length directions. The expansion under free exposure (no current) was determined to be a function of specimen size and of the direction of measurement relative to the cast specimen face.
Show less - Date Issued
- 1995
- PURL
- http://purl.flvc.org/fcla/dt/15214
- Subject Headings
- Concrete--Deterioration, Concrete--Corrosion, Seawater corrosion, Cathodic protection
- Format
- Document (PDF)
- Title
- Prestressing steel to concrete bond degradation due to cathodic polarization.
- Creator
- Joubert, Emmanuel., Florida Atlantic University, Hartt, William H.
- Abstract/Description
-
Experiments were conducted to evaluate occurrence of any deterioration of prestressing steel tendon to concrete bond as a consequence of cathodic polarization. Pretensionned concrete specimens were cathodically polarized with current densities ranging from 50 to 5000 m^2 of steel while exposed to a constant flow of natural sea water. The concrete and steel dimensional changes were monitored by strain gages mounted on the tendons and embedded in the concrete. Contractions of the steel of 25 to...
Show moreExperiments were conducted to evaluate occurrence of any deterioration of prestressing steel tendon to concrete bond as a consequence of cathodic polarization. Pretensionned concrete specimens were cathodically polarized with current densities ranging from 50 to 5000 m^2 of steel while exposed to a constant flow of natural sea water. The concrete and steel dimensional changes were monitored by strain gages mounted on the tendons and embedded in the concrete. Contractions of the steel of 25 to 50 percent of the initial tensioning were recorded after 17 to 36 MC/m^2 were transferred to the tendons on specimens polarized at the highest currents. This corresponds to 54 to 114 years of polarization at 10mA/m^2 if bond loss was solely dependent on the charge transfer. It was noticed that the smaller the current, the more the charge that was transferred before steel contraction began. These results imply that cathodic polarization should impose no threat to the prestressing steel-to-concrete bond on typical structures over their expected lifetime.
Show less - Date Issued
- 1995
- PURL
- http://purl.flvc.org/fcla/dt/15209
- Subject Headings
- Prestressed concrete, Steel--Corrosion, Cathodic protection
- Format
- Document (PDF)
- Title
- Hydrogen embrittlement of cathodically protected prestressing steel.
- Creator
- Kliszowski, Stanislas Henri., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Cathodic protection is currently recognized as the most practical mean for arresting corrosion of reinforcing steel tendons in existing concrete structures, however, its appropriateness in the case of prestressed concrete is questioned because prestressing steels are relatively susceptible to environmental cracking (hydrogen embrittlement). For the purpose of studying embrittlement tendencies a series of experiments using the slow strain rate technique were performed. The susceptibility to...
Show moreCathodic protection is currently recognized as the most practical mean for arresting corrosion of reinforcing steel tendons in existing concrete structures, however, its appropriateness in the case of prestressed concrete is questioned because prestressing steels are relatively susceptible to environmental cracking (hydrogen embrittlement). For the purpose of studying embrittlement tendencies a series of experiments using the slow strain rate technique were performed. The susceptibility to environmental cracking was compared for different steels corresponding to ASTM grades 270 and 250 polarized at $-$900 and $-1300$ mV (SCE) in deaerated saturated Ca(OH)$\sb2$ solutions. The influence of different notch and pit geometries was studied to simulate the behavior of corroded tendons and investigate the transition between smooth and severely notched specimen behavior. Also evaluated was the evolution of the mechanical properties of tendons after excessive polarization. The different cracking processes are discussed based on test data, fractography and exposures conditions associated with concrete structures.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/14999
- Subject Headings
- Cathodic protection, Metals--Hydrogen embrittlement, Tendons (Prestressed concrete), Prestressed concrete--Deterioration, Prestressed steel construction
- Format
- Document (PDF)