Presuel-Moreno, Francisco

An experiment was conducted to evaluate the durability, toughness, and strength
of Synthetic Fiber Reinforced Concrete after being immersed in five separate
environments for one year at FAU SeaTech. The specimens were molded and reinforced
with two-inch Polypropylene/Polyethylene Fibers in a concrete aggregate matrix and
were cut into identical sizes. Some of these environments had accelerated parameters
meant to increase degradation to simulate longevity and imitate harsh environments or
seawater conditions. The environments consisted of: a high humidity locker (ideal
conditions), submerged in the Intracoastal Waterway (FAU barge), seawater immersion,
a wet and dry seawater immersion simulating a splash/tidal zone, and another in low pH
seawater. The latter three were in an elevated temperature room (87-95°F) which
produced more degradative properties. The specimens were monitored and the
environments were controlled. The specimens were then evaluated using the IDT test
method using force to initiate first-cracking and post-cracking behaviors.

Dry-cast reinforced concrete pipes (D-C-RCP) have been used as drainage pipes by the
Florida Department of Transportation and other DOTs in the United States. Corrosion of the
steel reinforcement embedded in concrete is a major economic burden for bridges and other
structures subjected to de-icing salts, or harsh marine environments. This study investigates the
corrosion propagation of instrumented specimens obtained from segments of two types of D-CRCPs
(Types F and C). The objectives of this study are to better understand the mechanism of
corrosion propagation in D-C-RCPs and to identify the factors that affect the corrosion
propagation. Potential, depolarization, linear polarization resistance (LPR) and electrochemical
impedance spectroscopy (EIS) measurements were carried out to monitor the corrosion condition
and the mechanistic properties of the reinforcement. A galvanostatic approach was used to
accelerate the chloride transport to the steel surface until corrosion initiated. Once the specimen
was declared active, the electric field was suspended. For ~250 days, the corrosion was
monitored in the laboratory environment. The specimens were then transferred to a high
humidity chamber and anodically polarized with a galvanostat to accelerate the corrosion
propagation. The specimens were disconnected every two weeks to perform depolarization, LPR
and EIS measurements. In the high humidity environment, type F specimens are exhibiting a
higher corrosion rate most likely due to the smaller concrete cover allowing the chlorides to
reach the steel rebar surface quicker and reach a higher chloride concentration. Results will be
compared with conventional gravimetric weight loss measurements.

Flexible fillers has recently been implemented as corrosion protection for post-tensioning
tendons used in bridge structures in Florida. There are two different explanations why
corrosion could take place: 1. water is able to reach the steel 2. Microbiologica l ly
Influenced Corrosion.
The aim of this research is to evaluate corrosion protection effectiveness of five differe nt
microcrystalline waxes under different environmental conditions. Specimens tested ranged
from 7-wire steel strands to single wires (12-16 cm). Another aim is the appraisal of wax
degradation by fungi species. Single wires coated with each of the investigated protection
materials, were sprayed with suspensions of three different fungi species and a mix of them.
For single wires, independent of the environmental condition the specimen with more
corrosion was Nontribos, as well as the filler coated wires contaminated with Fungi. Fungi
species investigated were able to utilize the waxes as carbon source and caused differe nt
extents of MIC.

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.

Highway drainage pipes utilize concrete reinforced with steel wire to help mitigate water,
earth, and traffic loads. Drainage pipes reinforced with zinc electroplated steel fibers
offer a lower steel alternative to traditional steel wire cage reinforcements. The objective
of the thesis research was to determine the physical and electrochemical characteristics of
zinc electroplated steel fiber corrosion propagation. Experimental programs include:
Fracture analysis of zinc electroplated steel fibers embedded in dry-cast concrete pipes
exposed to varying chloride concentrations; Visual analysis of zinc electroplated steel
fibers embedded in concrete exposed to varying chloride concentrations; Electrochemical
analysis of zinc electroplated steel fibers embedded in concrete exposed to varying
chlorides; Chloride threshold determination for zinc electroplated steel fibers immersed
in simulated pore solution. Between the four experimental programs the most significant
conclusion is that oxygen, moisture, and chlorides past the chloride threshold must be
present for corrosion to propagate significantly on the zinc electroplated steel fibers.

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.

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.

Instrumented dry-cast reinforced concrete pipe (DC-RCP) specimens in which
corrosion of the reinforcing steel had initiated were selected to accelerate the corrosion.
Type C and type F DC-RCP were used. An anodic current density of various magnitudes
(0.5 μA/cm2, 1 μA/cm2 and 2.5 μA/cm2) was applied during the corrosion propagation
stage. The specimens were placed in high humidity and selected specimens were later
covered with wet sand. Selected specimens were terminated for visual examination and
gravimetric analysis. Typically, the reinforcement potentials during the accelerated
corrosion period were more negative for F specimens compared to C specimens. The C
specimens experienced ~2× more corrosion than the F specimens. The accumulated
corrosion products did not cause cracks. A method was developed that allows for modest
corrosion acceleration during the corrosion propagation stage of DC-RCP.

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.