Exam (elaborations)
CIV1252 - Infrastructure Renewal Assignment 1
- Institution
- University Of Toronto (U Of T )
Exam of 7 pages for the course APS1252 - Infrastructure Renewal at U of T (N/A)
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CIV 1252H Infrastructural RenewalTerm Project#1 – Planning a Successful Condition Survey
Submission Date: Oct 13th,2022
General Physical Condition
The subjective bridge in Southern Ontario requires a condition performance assessment to identify its
potential structural defects and serviceability deficiency. The critical information of the study objective
will be briefly discussed below:
The bridge is in good condition, with a small portion of visible deterioration on the exposed
concrete surface. The latest corrosion repair for the epoxy-coating steel reinforcement of the
bridge deck was completed in 2005.
The fictional bridge location is based in Southern Ontario. Therefore, the highest and lowest
temperature is estimated as 30 degrees Celsius and -20 degrees Celsius, respectively.
The bridge is only 40 years old, so major components' life-cycle renewals are not yet expected.
The approximate area of the bridge deck is 95.2 square meters with a 41.2-meter perimeter.
The underside of the bridge deck does not have any visible delamination and spalling for the
concrete structure. Still, the rust stain is shown on the abutment's splash zone since it has
moisture and oxygen.
Corrosion Investigation – Cause & Severity
Cause of First, the leading corrosion cause in the subjective bridge is the corrosion of the steel
the reinforcement, which usually happens as electrolytic because of the migration of
corrosion chloride ions to concrete-enclosed steel rebar. The chloride ions(usually from deicing
material) can penetrate the concrete until they reach the embedded steel without
destroying the structure's integrity. Then the pH will drop below the threshold level for
initiative corrosion due to the presence of the chloride ions. Meanwhile, The nearby lake
water and oxygen can diffuse through the porous of the concrete and evaporate, which
accelerates aggressive electrochemical reactions in the concrete for rusting the steel.
Second, carbonation is another common cause of steel corrosion when hydrated
portland cement reacts with the CO2 in the air. It will decrease pH for the initiation of
the corrosion reaction and might lead to structural failure within the predicted service
life. In our case, CO2 absorbed by rain enters the nearby lake as carbonic acid, and
decaying vegetation releases carbon back into the atmosphere. These concentrations of
CO2 and high relative humidity will decrease the concrete structure's pH for the
initiation of steel corrosion.
Third, cement can act as a protective oxide coating for the steel reinforcement at a pH of
13-14. Steel corrosion only occurs when the pH is below 10, but the pH of fresh water is
usually between 6 to 8. The studied bridge is exposed to the lakewater, which is
evaluated as one of the scenarios for the longevity of the concrete bridge. The pH value,
purity, acidity, and conductivity of the lakewater define the extent of corrosion in the
reinforcing steel.
, Lastly, epoxy-reinforcement steel can protect these structures against corrosion damage,
but they are not immune the corrosion. The bridge has 40 years of service history. The
bridge deck surface is observed as visible deterioration, such as abrasion, scaling, and
cracking, which allows chloride-contaminated water to corrupt the coated steel. These
common deterioration problems are caused by repeated freeze/thaw cycles, deicing
salts, increased traffic load, and chemical reactions caused by sulfate action. The
corrosion of coated bars increased every 2 and 4.5 years of exposure to the
contaminated resource.
Destructiv Visual and tactile inspection: The presence of rust stains or efflorescence are evidence
e or Non- of possible reinforcement corrosion. The inspector should document the approximate
Destructiv location and severity of distress or deterioration, such as the bridge's spalling, cracking,
e and delamination. Also, he should observe and measure the embedded post-tension
Methods components. The final deliverable should contain the photos, location sketch,
for measurement, and video.
Corrosion
Half-cell test: Half-cell corrosion detection is not recommended for epoxy-coated
reinforcement because epoxy-coated bars are electrically insulated. Our studied bridge is
considered a more deteriorated model as the exception since most of the coating no
longer serves the original function. The half-cell test will be performed to identify the
reinforcement corrosion of the bridge deck by one of the inspectors.
Chloride Content & pH Testing: Inspector can use the field test kits to quickly test on-site
and determine the chloride and pH levels of the selected component immediately.
Suppose the half-cell test shows contradictory results against chloride content. In that
case, the sample should be collected for the laboratory test using wet chemical analysis
since it provides a more accurate result. Also, we can measure the reduction in steel
sectional area from the core sample and then verify the extent of corrosion.
Alkali-aggregate Resistivity
Destructive Visual and tactile inspection. Three common visual observations will be listed below to
or Non- identify the presence of Alkali-silica Reaction(ASR) and Alkali-carbonate Reaction(ACR).
Destructive Map or pattern cracking, the general appearance of swelling of concrete
Methods Map or pattern cracking expands freely; silica gel leaches from cracks and
for Alkali- calcium hydroxide-depleted paste
aggregate Map or pattern cracking, general disintegration of concrete
Resistivity
Ultrasonic Surface Wave(USW): One inspector will perform a USW test for the bridge
deck to assess the properties of concrete, including the changes in modulus caused by
mix design compaction, curing, and stress-related cracks. The measured acoustic
nonlinearity parameter is well-correlated with the reduction of the compressive
strength induced by ASR damage.
Electrical Charge Permeability Test: Low permeability concrete is less likely to
deteriorate caused of environmental factors such as corrosion, freeze-thawing, or ASR.
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