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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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Bulk diffusion of high performance concrete specimens exposed to different levels of sodium chloride and seawaterUnknown Date (has links)
The purpose of this study was to investigate the performance to chloride
penetration of specimens made with three base compositions (three different
supplementary cementitious materials) and water to cementitious ratios of 0.35, 0.41, or
0.47. The specimens were subjected to bulk diffusion test or full immersion. The mixes
were exposed to 0.1 M, 0.6 M, or 2.8 M sodium chloride solution for different periods of
time. Also, partially immersed specimens were exposed to indoor and outdoor exposures
(tidal, splash, barge). Chloride concentration profiles were obtained and the apparent
diffusion coefficient was calculated. The skin effect was found only on some chloride
profiles exposed to 0.1 M sodium chloride solution. The chloride binding capacity was
calculated; specimens with 20% Fly Ash and 8% Silica Fume had the highest binding
capacity (70.99%). The apparent diffusivity coefficient was found to be dependent on the
curing regime as well as the water to cement ratio. The correlation between effective
resistivity and apparent diffusion coefficient was determined. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / 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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Corrosion initiation and propagation on corrosion resistant alloys embedded in concrete by accelerated chloride transportUnknown Date (has links)
Two duplex stainless steels rebars: UNS32304SS and UNS32101SS, were selected to investigate the corrosion initiation and propagation in reinforced concrete specimens. The investigation is divided in two phases with two different methods to accelerate the transport of chlorides through the concrete and initiate corrosion in a short period of time. After corrosion had initiated and propagated for some time; selected specimens were terminated for visual examination. On specimens selected for autopsy, the rebars in the top row showed corrosion to various degrees. Corrosion had propagated to such extent on the terminated specimens that the specimen showed cracks. Stray current might have caused accelerated corrosion on rebars where corrosion had initiated. Based on chloride concentrations measured at the rebar trace, corrosion initiated: on S32101 rebars on average at 7.9 kg/m3, and S32101 rebars on average at 6.0 kg/m3. The findings suggest that S32304 rebars corroded at a slower than S32101. / by Francisco Gutierrez Tellez. / Thesis (M.S.C.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
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Centrally prestressed fiber reinforced concrete columnsUnknown Date (has links)
With the need to improve corrosion resistance in columns and piles, the innovative idea of Centrally Prestressed Fiber Reinforced Concrete (CPFRC) columns is a promising solution. The first step is to compare if the compressive strength of any mix is affected by the size, geometry, or even the inclusion of polyolefin fibers in a specimen. The results showed that the cylinder size of 4 in. x 8 in., which is the most common size used by the testing labs, has the highest compressive strength. There was no sign on compressive strength improvement with the use of polyolefin fibers, except for reduction in cracking size and concrete spalling. The second step compared the ultimate strength, ductility characteristics and failure mode of CPFRC columns to conventional columns. CPFRC showed adequate axial and flexural resistance, in addition to ductile behavior similar to regular reinforced concrete columns. / by Daniel A. Grijalba. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.
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Chloride penetration into concrete structures exposed to the marine atmosphereUnknown Date (has links)
Chloride ions present in the marine atmosphere contained in marine aerosols is
investigated for a relationship with chloride that accumulated into concrete. Chloride
profiles are conducted on several concrete mixes containing fly ash, silica fume, and slag,
with water to cementitious ratios of 0.35, 0.41, and 0.47. The chloride accumulation in
concrete samples exposed to the environment is investigated with relation to the chloride
deposition from the marine atmosphere measured via the wet candle test. Results indicate
a possible relationship for the total accumulated chloride in the concrete with the
accumulated chloride deposition (wet candle). Over the exposure periods, concrete
specimens with 50% slag addition and 0.47 w/cm had the lowest average rates of chloride
accumulation for deposition under 100 g/m2day. Chloride accumulation was lower in
concrete containing 20% fly ash and 8% silica fume with 0.35 w/cm for chloride deposition
rates over 200 g/m2day. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
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Initiation and propagation of corrosion in dry-cast reinforced concrete ring specimensUnknown Date (has links)
The corrosion propagation stage of D-CRP (types F and C) was tested under
immersion in water, high humidity, and covered with wet sand. The half-cell potential,
linear polarization test, and electrochemical impedance spectroscopy measurements were
performed. Selected specimens were terminated after 300 days of exposure and visually
inspected. Based on corrosion potential measurements obtained during the corrosion
propagation observation, and calculated corrosion rate based on LPR measurements: all
specimens were actively corroding. Additionally, EIS-Rc values were calculated for FS,
CS and CH specimens. The Rc_EIS were generally greater than Rc_LPR values. EIS
spectra for CI and FI specimens usually included mass transport limitations, as these
specimens were immersed. Both type of specimens immersed in water (FI and CI), appeared to have higher corrosion rate based on LPR-Rc. However, upon autopsy
it was revealed that a more modest amount of corrosion occurred on the reinforcing steel
of FI and CI terminated specimens. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
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Flexural Strength, Ductility, and Serviceability of Beams that Contain High-Strength Steel Reinforcement and High-Grade ConcreteYosefani, Anas 06 June 2018 (has links)
Utilizing the higher capacity steel in design can provide additional advantages to the concrete construction industry including a reduction of congestion, improved concrete placement, reduction in the required reinforcement and cross sections which would lead to savings in materials, shipping, and placement costs. Using high-strength reinforcement is expected to impact the design provisions of ACI 318 code and other related codes.
The Applied Technology Council (ATC-115) report "Roadmap for the Use of High-Strength Reinforcement in Reinforced Concrete Design" has identified key design issues that are affected by the use of high-strength reinforcement. Also, ACI ITG-6, "Design Guide for the Use of ASTM A1035 Grade 100 Steel Bars for Structural Concrete" and NCHRP Report 679, "Design of Concrete Structures Using High-Strength Steel Reinforcement" have made progress towards identifying how code provisions in ACI 318 and AASHTO could be changed to incorporate high-strength reinforcement.
The current research aims to provide a closer investigation of the behavior of beams reinforced with high-strength steel bars (including ASTM A615 Grade 100 and ASTM A1035 Grades 100 and 120) and high-strength concrete up to 12000 psi. Focus of the research is on key design issues including: ductility, stiffness, deflection, and cracking.
The research includes an extensive review of current literature, an analytical study and conforming experimental tests, and is directed to provide a number of recommendations and design guidelines for design of beams reinforced with high-strength concrete and high-strength steel. Topics investigated include: strain limits (tension-controlled and compression-controlled, and minimum strain in steel); possible change for strength reduction factor equation for transition zone (Φ); evaluation of the minimum reinforcement ratio (þmin); recommendations regarding limiting the maximum stress for the high-strength reinforcement; and prediction of deflection and crack width at service load levels. Moreover, this research includes long-term deflection test of a beam made with high grade concrete and high-strength steel under sustained load for twelve months to evaluate the creep deflection and to insure the appropriateness of the current ACI 318 time-dependent factor, λ, which does not consider the yield strength of reinforcement and the concrete grade.
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Procedures for diagnosis and assessment of concrete buildings / Wen-Gang HuaHua, Wen-Gang January 1993 (has links)
Bibliography: leaves 213-234 / xviii, 234, 13 leaves ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Faculty of Engineering (Civil), 1994?
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Prediction of low temperature cracking of asphalt concrete mixtures with thermal stress restrained specimen test resultsKanerva, Hannele K. 21 June 1993 (has links)
Low temperature cracking is attributed to tensile stresses induced in an
asphalt concrete pavement that develop when the pavement is subjected to a cold
temperature. Cracking results in poor ride quality and a reduction in service life of
the pavement. Low temperature cracking has been predicted by regression
equations, mechanistic approaches and by simulation measurements. The purpose of
the study reported herein is to (1) evaluate the Thermal Stress Restrained Specimen
Test (TSRST) as an accelerated performance test to simulate low temperature
cracking of asphalt concrete mixtures and (2) develop a deterministic and
probabilistic model to predict low temperature cracking with TSRST results.
Construction histories, cracking observations and temperature data were
collected for five test roads in Alaska, Pennsylvania and Finland. A full scale and
fully controlled low temperature cracking test program was conducted at the U.S.
Army Cold Regions Research and Engineering Laboratory (USACRREL).
Specimens were fabricated in the laboratory with original asphalt cements and
aggregates from the test roads. In addition, asphalt concrete pavement specimens
were cut from the test sections. The TSRST results obtained for these samples were
correlated with the field observations. Based on a statistical analysis of the data, the
TSRST fracture temperature is associated with the field cracking temperature and
crack frequency for the test roads where mixture properties dominated low
temperature cracking. It was concluded that the TSRST can be used to simulate low
temperature cracking of asphalt concrete mixtures.
A deterministic and a probabilistic model were developed to predict crack
spacing as a function of time using the TSRST results, pavement thickness and bulk
density, pavement restraint conditions and air temperature. The affect of aging on
pavement properties was incorporated in the models by predicting the field aging
with Long Term Oven Aging (LTOA) treatment in the laboratory. The calculation
of the crack spacing is based on the theory that the pavement slab cracks when the
pavement temperature reaches the cracking temperature of the mixture and the slab
is fully restrained. The deterministic model predicts crack spacing with time
whereas the probabilistic model predicts crack spacing and its variation with time
and yields the reliability of the design with regard to a minimum acceptable crack
spacing criterion defined by road authorities.
The models were verified by comparing the predicted crack spacings for the
five test roads to the observed crack spacings. The probabilistic model is
recommended for use in predicting the low temperature cracking of asphalt concrete
mixtures. / Graduation date: 1994
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