54 CHAPTER 5 EXPERIMENTAL SETUP AND PROCEDURES 5.1 GENERAL The experimental setup and procedures for conducting various tests on concrete and RCC elements are discussed here. 5.2 EXPERIMENTAL SETUP FOR CONCRETE SPECIMENS 5.2.1 Concrete and Mortar Cubes The size of mortar cubes used for this investigation was 70.6 x 70.6 x 70.6 mm confirming to IS 10080-1982. Compressive strength of mortar cubes were found according to IS: 4031-1982 (Part 6). Similarly, to determine the compressive strength and durability effects of concrete, 150 mm × 150 mm × 150 mm size concrete cubes were cast and tested in accordance with IS: 516-1959. All strength tests were conducted using 2000kN compression testing machine. Cube moulds of size 150x150x150 mm were used. They were cleaned thoroughly using a waste cloth and then properly oiled along its faces. Concrete was then filled in mould and then compacted using a standard tamping rod of 60 cm length having a cross sectional area of 25mm 2 . Concrete mixtures with different proportions of copper slag ranging from 0% to 60% replacement for sand and 0% to 20% for cement were prepared and tested.
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54
CHAPTER 5
EXPERIMENTAL SETUP AND PROCEDURES
5.1 GENERAL
The experimental setup and procedures for conducting various tests
on concrete and RCC elements are discussed here.
5.2 EXPERIMENTAL SETUP FOR CONCRETE SPECIMENS
5.2.1 Concrete and Mortar Cubes
The size of mortar cubes used for this investigation was 70.6 x 70.6
x 70.6 mm confirming to IS 10080-1982. Compressive strength of mortar
cubes were found according to IS: 4031-1982 (Part 6). Similarly, to determine
the compressive strength and durability effects of concrete,
150 mm × 150 mm × 150 mm size concrete cubes were cast and tested in
accordance with IS: 516-1959. All strength tests were conducted using
2000kN compression testing machine. Cube moulds of size 150x150x150 mm
were used. They were cleaned thoroughly using a waste cloth and then
properly oiled along its faces. Concrete was then filled in mould and then
compacted using a standard tamping rod of 60 cm length having a cross
sectional area of 25mm2. Concrete mixtures with different proportions of
copper slag ranging from 0% to 60% replacement for sand and 0% to 20% for
cement were prepared and tested.
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5.2.2 Concrete Cylinders
The size of cylinder used for split tensile strength and durability
studies was 150mm diameter and 300mm height. This test was conducted in
accordance with IS: 5816-1999. The crude oil was applied along the inner
surfaces of the mould for the easy removal of specimens from the mould.
Concrete was poured throughout its length and compacted well.
For corrosion test, 12mm diameter bars of Fe 250 grade of steel
were embedded at the centre of the specimens with 70mm cover thickness.
5.2.3 Concrete Discs
Disc shaped specimens of nominal size 100mm diameter x 50mm
thickness was used to carry out RCPT test in concrete in accordance with
ASTM C-1202. Moulds are made by using PVC. The crude oil was applied
earlier along the inner surfaces of the mould for the easy removal of
specimens from the mould.
5.2.4 Concrete Beams
Concrete beams of standard size 750 x 150 x 150 mm confirming to
IS: 516-1959 was used for this study. A total number of 21 specimens were
cast for different proportions of copper slag with sand in each series. Out of
which, three specimens were treated as controlled specimens. Seven test groups
were constituted with replacement of 0% (control specimen), 10%, 20%, 30%,
40%, 50% and 60% copper slag with sand in each series. Three specimens
were prepared for every replacement percentage and these beams were tested
for flexural strength in Universal Testing Machine of capacity 100 tonnes.
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5.3 EXPERIMENTAL SETUP FOR RCC SPECIMENS
5.3.1 RCC Beams
Two types of RCC structural elements have been considered for
study.
They are:
• Flexural behaviour of RCC beams incorporating copper slag
as partial replacement of sand. (Replacement – 0 to 60%)
• Flexural behaviour of RCC beams incorporating copper slag
as partial replacement of cement (Replacement - 0 to 20%)
Simply supported RCC beams were subjected to pure flexural
failure by subjecting them to two point loading test. The beams used in this
study were 150mm x 150mm in cross section and 1500mm in length. Two
10 mm diameter bars were used for flexural reinforcement at bottom and two
8 mm rods were provided for top reinforcement. For each beam, 6 mm
diameter mild steel bars are used as stirrups, spaced 100 mm c/c for shear
reinforcement. Typical beam reinforcement details are illustrated in
Figure 5.1. For this investigation, a total number of 36 beam specimens were
cast and tested for sand and cement replacement (18Nos. - sand replacement,
12Nos.-cement replacement, 3Nos. - combined replacement and 3Nos.-
controlled specimens). All beams were cast by using M20 grade concrete with
20 mm size of CA, locally available sand and OPC 43 grade cement.
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Figure 5.1 Beam reinforcement details
5.3.1.1 Experimental set up of RCC beam
All beams (150mm x 150mm in cross section and 1500mm in
length) were tested as simply supported beams under two point loading over
an effective span of 1400mm. The loads were applied at a distance of 470mm
on either side of the mid span of the beams of 1500mm length, as shown in
Figure 5.2. To study the performance of copper, slag replaced specimens.
These beams were tested in a loading frame of 500 kN capacity. The loads
were monitored through a high accuracy load cell with a load sensitive of 0.1
tonnes. For this case, mid span deflection was measured using dial gauges of
least count 0.01mm. The parameters such as initial cracking load, ultimate
load and the deflected shape of the specimens were noted.
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Figure 5.2 Experimental set up of RCC beams
5.3.2 RCC Short Columns
To find axial compressive strength, columns with square cross
section of size 100mm x 100mm cross section and 1000mm long were used.
The head was provided at each end of columns with the size of 140mm x
100mm x100mm to avoid crushing failure. All the columns were provided
with four 8mm diameter Tar steel Fe 415 as longitudinal and 6mm diameter
mild steel rods Fe 250 as transverse reinforcement with spacing of 100mm
centre-to-centre distance. A 20mm effective cover for reinforcements was
provided. L/D ratio maintained for this type of column was 10. A total
number of 21 specimens were cast for different proportions of copper slag
with sand in each series. Three specimens were treated as controlled
specimens. The reinforcement details of the columns are shown in Figure 5.3.
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Figure 5.3 Reinforcement details of short columns
5.3.2.1 Experimental set up of RCC short columns
All the columns were tested under pure axial compressive load. The
columns were tested in a column tester of 2000 kN capacity. The load was
applied gradually in a controlled manner in increments of 2kN by hand
pumping of the manually operated hydraulic jack. The loading was monitored
through a high accuracy load cell with a sensitivity of 1kN. The axial strain
values were measured from the compressometer positioned at mid height of
column for various loads taken from the proving ring. The lateral
deformations were measured by dial gauges of least count 0.01mm fixed at
adjacent faces of the columns as shown in Figure 5.4. The parameters such as
initial cracking load, ultimate load and the deflected shape of the specimens
were noted.
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Figure 5.4 Experimental set up of RCC short columns
5.3.3 RCC Long Columns
The following types of columns have been considered for
investigation of failure due to buckling.
• Buckling behaviour of RCC long columns incorporating
copper slag as partial replacement of sand. (Replacement - 0
to 60%)
• Buckling behaviour of RCC long columns incorporating
copper slag as partial replacement of cement (Replacement - 0
to 20%)
To find axial compressive strength, columns with square cross
section of size 150mm x 150mm cross section and 1900mm long were used.
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The head was provided at each end of columns with the size of 240mm x
200mm x175mm to avoid crushing failure. L/D ratio maintained for this
column was 12.67. Therefore, this column is otherwise called long columns.
All the columns were provided with four 10mm diameter Tar steel Fe 415 as
longitudinal and 6mm diameter mild steel rods Fe 250 as lateral ties for
transverse reinforcement with spacing of 100mm centre-to-centre distance.
These column specimens were cast by using specially fabricated steel moulds.
The details of the geometry of the column specimens and details of
reinforcement used for the specimens are shown in Figure 5.5. For this
investigation, a total number of 36 column specimens were cast and tested for
sand and cement replacement (18Nos. - sand replacement, 12Nos.-cement
replacement, 3Nos. - combined replacement and 3Nos.-controlled specimens).
Figure 5.5 Reinforcement details of RCC long columns
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5.3.3.1 Experimental set up of RCC short columns
All the columns were tested under pure axial compressive load. The
columns were tested in a column tester of 2000 kN capacity. The load was
applied gradually in a controlled manner in increments of 2kN by hand
pumping of the manually operated hydraulic jack. The loading was monitored
through a high accuracy load cell with a sensitivity of 1kN. The lateral
buckling deformations were measured by LVDTs of least count 0.01mm fixed
at adjacent faces of the columns at mid span as shown in Figure 5.6. The
parameters such as initial cracking load, ultimate load and the deflected shape
of the specimens were noted. Cracks formed on the surfaces were marked and
identified. The load and deflection characteristics were studied.
Figure 5.6 Experimental up of RCC long set columns
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5.4 EXPERIMENTAL PROCEDURES
5.4.1 Compressive Strength Test
Concrete cubes of size 150mm×150mm×150mm were cast with
and without copper slag. During casting, the cubes were mechanically
vibrated using a table vibrator. After 24 hours, the specimens were demoulded
and subjected to curing for 28 days in portable water. After curing, the
specimens were tested for compressive strength using compression testing
machine of 2000KN capacity. The maximum load at failure was taken. The
average compressive strength of concrete and mortar specimens was
calculated by using the following equation 5.1.
Ultimate compressive load (N)
Compressive strength (N/mm2) = (5.1)
Area of cross section of specimen (mm2)
The tests were carried out on a set of triplicate specimens and the
average compressive strength values were taken.
5.4.2 Split Tensile Strength Test
Concrete cylinders of size 150 mm diameter and 300mm length
were cast with incorporating copper slag as partial replacement of sand and
cement. During casting, the cylinders were mechanically vibrated using a
table vibrator. After 24 hours, the specimens were demoulded and subjected
to curing for 28 days in portable water. After curing, the cylindrical
specimens were tested for split tensile strength using compression testing
machine of 2000kN capacity. The ultimate load was taken and the average
split tensile strength was calculated using the equation 5.2.
2P
Split tensile strength (N/mm2) = (5.2)
Π LD
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where,
P=Ultimate load at failure (N),
L=Length of cylindrical specimen (mm),
D=Diameter of cylindrical specimen (mm).
The tests were carried out on a set of triplicate specimens and the
average tensile strength values were taken.
5.4.3 Ultrasonic Pulse Velocity Test
This test was conducted as per the procedure given in IS:
13311:1992. Ultrasonic Pulse Velocity (UPV) is a non-destructive technique
that measures involves measuring the speed of sound through materials in
order to predict material strength, to detect the presence of internal flaws such
as cracking, voids, honeycomb, decay and other damage. The instrument
consists of a transmitter and a receiver (two probes). The time of travel for the
wave to pass from the transmitter to the receiver when kept opposite to each
other is recorded in the ultrasonic instrument (Limaye 2002). The distance
between the two probes (path length) was physically measured. Hence,
Ultrasonic Pulse Velocity = Path length / Transit time (5.3)
This velocity is related to its compressive strength. The quality and
approximate compressive strength of concrete was determined by using
Table 5.1 which gives the relationship between ultrasonic pulse velocity and
quality of concrete as per IS: 13311:1992.
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Table 5.1 Relationship between ultrasonic pulse velocity and quality of
concrete as per IS: 13311:1992
Longitudinal pulse
velocity km/sec
Approximate
compressive strength
N/mm2
Quality of
concrete
Below 2.0 --- Very poor
2.0 to 3.0 4.0 poor
3.0 to 3.5 Upto 10 Fairly good
3.5 to 4.0 Upto 25 good
4.0 to 4.5 Upto 40 Very good
Above 4.5 > 40 Excellent
5.4.4 Open Circuit Potential (OCP) Test
The standard test is given in ASTM C 876 and is illustrated in
Figure 5.7. The apparatus includes a copper-copper sulphate half-cell,
connecting wires and a high impedance voltmeter. The positive terminal of
the voltmeter is attached to the reinforcement and the negative terminal is
attached to the half-cell. A high impedance voltmeter is used so that very little
current runs through the circuit. The half-cell makes electrical contact with
the concrete by means of a porous plug and a sponge moistened with a wet
solution (such as liquid detergent). Cylindrical reinforced concrete specimens
of size 100mm diameter and 300 mm height were cast in triplicate with
various replacement percentages of copper slag with sand and cement. For
this investigation, 12mm diameter of Fe 250 TMT bars are embedded into the
concrete with cover thickness of 60mm. All the triplicate specimens were
taken out and then dried. The potential of the embedded rebar was measured
against saturated calomel electrode (SCE) using a high impedance voltmeter
before keeping the specimens in 3.5% of NaCl solutions. Then, the specimens
were subjected to alternate wetting (5 days) and drying (5 days) in 3% NaCl
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solutions in order to induce accelerate corrosion. The potential readings were
measured periodically (Nicholas 1999). The experiment is continued for a
period of 90 days. Potential measurements were carried out at an ambient
temperature of 32+1°C. Table 5.2 shows the relationship between potential
values and probability of corrosion.
Figure 5.7 OCPT test apparatus
Table 5.2 Relationship between for OCP values and probability of
corrosion
OCP values
(mV vs. SCE)
Corrosion condition as per
ASTM C876-1995
< -426 Severe corrosion
< -276 High (90% risk of corrosion)
-126 to -275 Intermediate corrosion risk
> -125 Low(10% risk of corrosion)
5.4.5 Accelerated Corrosion Process: Gravimetric Weight Loss Method
This investigation was carried out as per ASTM G1-90. The weighed
TMT steel specimens were embedded in concrete cylinder of size 150mm
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diameter and 300 mm height. The reinforced concrete samples (Figure 5.8) were
subjected to alternate wetting and drying exposure in 3.5% NaCl solution.
Regular D.C power supply of 12V is supplied continuously throughout the
corrosion period of 15 days. Positive terminal of voltmeter is connected with
soldered wires and negative terminal is connected with copper plate (cathode).
After the process of accelerated corrosion, all the specimens were disconnected
and removed from tank. After the corrosion period, the rod was taken out and
weighed. The loss in weight was calculated. From the weight loss values,
(ASTM G-1) the corrosion rates were obtained from the relationship
(K * W )
Corrosion rate = mm/yr (5.4)
(A*T*D)
where K is a constant, K =87.6 in case of expressing corrosion rate in mm/yr
T is the exposure time expressed in hours,
A is the surface area in cm2, W is the mass loss in milligram and
D is the density of the corroding metal (7.85g/cm3)
Figure 5.8 Reinforced concrete samples for corrosion test
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5.4.6 Rapid Chloride Penetration Test
Concrete disc specimens of size 100mm diameter and 50mm thick
(Figure 5.9) were cast for various replacement percentages of sand and
cement with copper slag in concrete. After 24 hours, the disc specimens were
removed from the mould and subjected to curing for 90 days in chloride free
distilled water. After curing, the specimens were tested for chloride
permeability. All the specimens were dried free of moisture before testing.
Figure 5.9 Concrete disc specimen for RCPT test
The test set up is called Rapid Chloride Penetration Test (RCPT)
assembly. This is two-compartment cell assembly. Disk specimen is
assembled between the two compartments cell assembly and checked for air
and watertight. The cathode compartment is filled with 3%NaCl solution and
anode compartment is filled with 0.3 normality NaOH solutions. Then, the
concrete specimens were subjected to RCPT by impressing a 60V from a DC
power source between anode and cathode. Current recorded over a period of 6
hours at an interval of 30 minutes as per the procedure given in ASTM C1202
(Table 5.3). This test was conducted at CECRI, Karaikudi, Tamil Nadu.
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Table 5.3 Charge passed through RCPT test as per ASTM C1202
S.No Charge passed
coulombs
Chloride ion
penetrability
1 >4000 High
2 2000-4000 Moderate
3 1000-2000 Low
4 100-1000 Very low
5 <100 Negligible
From the current values, the chloride permeability is calculated in
terms of coulombs at the end of 6 hours by using the following equation 5.5.