All of the testing in phase 1, except for the shear beams (tested April 21 2010), was carried out during the period of March 17-19, 2010 in the laboratory at The Department of Structural Engineering at NTNU.
The following tests were performed:
• Compressive strength; compression of standard cylinders and cubes.
• Flexural tensile strength; 3-point bending of small scale bending prisms.
• Uniaxial tensile strength; tensile test of small scale tension prisms.
• Shear strength; 4-point bending of shear beams.
• Flexural toughness; centric point loaded round panels supported on three pivots.
When unpacking all the test specimens the storage conditions was been found to be adequate according to the requirements set by the governing standards, i.e. ≥95% humidity.
All the results from test phase 1 is summarized and discussed further in Chapter 6.8.
6.7.1 Compressive Strength
A total of 12 cubes and 9 cylinders were tested March 17-19 in order to establish the compressive strength of the different concrete recipes. A secondary objective was to compare the correlation between cylinder and cube compression strength for the W900 and W1150 with the LWC correlations in Eurocode 2 [2]. The tests were performed in accordance with the European Standard NS-EN 12390-3 [20] in a uniaxial compression testing machine. The testing rig is made by Galdabini and is shown in Fig. 31. This is an analog machine so no other logging than the actual failure load and visual observation was done.
The rest of the cube specimens which had not been tested were cured until the day of the shear beam testing (April 21) in order to have reference data on the compression strength development for the W900 and W1150 concrete. In this second curing phase from 28 to 62 days of curing, the cubes were not stored submerged in water. The cubes were stored in wet cloths and wrapped in plastic to ensure sufficient humidity, i.e. ≥95% humidity. During these compression test, the Galdabini machine stopped working. The rest of the compression tests were then performed with another equivalent analog uniaxial compression machine. More specifically a Mohr Federhaff Losenhausen with a maximum capacity of 300 000 kilopond.
6. Test Phase 1: Test Program for Material Data Determination
40
Fig. 31: Galdabini analog uniaxial compression testing machine.
6.7.2 Flexural Tensile Strength
A total of 9 small scale beams for testing of flexural tensile strength were tested in test phase 1.
The main objective of these tests was to determine the residual tensile strength of the LWAC with different fiber volume and density. A sketch of the testing arrangement and specimen geometry is shown in Fig. 32. A photo of the arrangement which was used in the laboratory at NTNU is shown in Fig. 33.
Fig. 32: Sketch of the testing arrangement for flexural tensile capacity of small scale beams [23].
41 Fig. 33: Photo of the flexural tensile test arrangement in the laboratory at NTNU.
The bending specimens were tested with an Instron 1126 multipurpose testing machine with a maximum load capacity of 250kN (hydro mechanical drive) together with an Instron 8800 controller for logging purposes. A universal bearing rig with sufficient stiffness especially made for these kinds of experiments were used to ensure a simply supported boundary condition for the beams. The bearing rig fulfills the requirements set by the governing standard NS-EN 14651[23].
The test was performed by applying the load indirectly by displacing the specimen at a constant rate. The load was measured by a load cell mounted behind the loading piston. The displacement was measured with two Linear Variable Differential Transformers (LVDT) mounted at a bracket at each side of the specimen in the longitudinal center over the notch. The vertical displacement is then measured as illustrated in Fig. 33 by a rigid steel plate mounted at the bottom the specimen, across the notch.
The tests were performed in accordance with the European Standard NS-EN 14651 [23], but with the exceptions shown in Table 8. The modifications were done in order to reduce testing time and reduce the number of sampling data points. This has been done since SINTEF researchers claimed that the specified modifications had a small/no influence on the test results, based on earlier experience [30].
Table 8: Exceptions made when testing the small scale flexural tensile beams.
Control Parameter
Governing method Method used
Operating speed 0-0.13mm deflection: 0.08mm/min 0.13–3.44mm deflection: 0.21mm/min
constant 0.21mm/min Sampling rate 0-0.13mm deflection: 5 Hz
0.13–3.44mm deflection: ≥ 1 Hz
constant 2 Hz
6. Test Phase 1: Test Program for Material Data Determination
42
6.7.3 Uniaxial Tensile Strength
A total of 9 uniaxial tensile prisms were tested in test phase 1 for determination of tensile strength and Young’s Modulus. The test was performed in accordance to a procedure developed by SINTEF at NTNU [22] mainly because of good experience gained with this testing procedure and the available rig equipment at the NTNU laboratory. This test method does not suggest a notch to be cut in the specimen, even though this is common in more well known testing methods such as RILEM TC 162-TDF [31].
To be able to measure the displacements in the cracked region it is decided to make an exception from the SINTEF method and cut a notch as described in Section 6.5.2. Previous experiments using the same exception have been carried out at NTNU with good results. No negative effects of the notch have been observed [32].
Other exceptions from the SINTEF method used in this report are summarized in Table 9.
Table 9: Exceptions made when testing uniaxial tension prisms.
Control Parameter Governing method Method used
Operating Speed SINTEF: 5mm/min
RILEM: 0-0.1mm deflection: 0.005mm/min 0.1mm→ deflection: 0.1mm/min
0.5mm/min
Sampling Rate RILEM: 0.5Hz 2 Hz
The uniaxial tensile specimens were tested with the same Instron testing machine and logging equipment as described in Section 0, but with another testing rig especially made for uniaxial tension testing. The bearing rig is made for this particular type of test and has been thoroughly tested at NTNU. The tension specimen is held in the rig by rubber covered steel plates with applied pressure by hydraulic jacks. No sliding was observed or recorded during the testing. A sketch of the testing arrangement and specimen geometry is shown in Fig. 34 together with the arrangement used at NTNU.
43 Fig. 34: Left: Sketch of tension test arrangement [13]. Right: Photo of the tension rig used in the
laboratory at NTNU.
The test was performed by applying the load indirectly by displacing the specimen at a constant rate. The load was measured by a load cell mounted behind the load piston while the displacement was measured with two LVDT’s mounted at a bracket at two of the specimen sides over a distance of 100mm over the notch, see Fig. 35. The measuring rig was removed when the LVDT measuring devices were outside their measuring range, approximately at a displacement of 6-7mm. After the LVDT’s had been removed the displacement was measured directly by the machine.
6. Test Phase 1: Test Program for Material Data Determination
44
Fig. 35: Measuring bracket mounted on the uniaxial tensile specimen within the test rig.
6.7.4 Flexural Toughness
A total of 9 round panels were tested for determination of flexural toughness, expressed through the energy absorption in the post crack phase of the fiber reinforced concrete. The tests were performed in accordance with the ASTM standard C1550-08 [24] with a minor exception related to the data sampling rate. The control parameters used during the tests are summarized in Table 10.
Table 10: Machine properties used during tests of round panels.
Control Parameter Governing method Method used
Operating Speed ASTM: 4.0±1.0 mm/min 4mm/min
Sampling Rate ASTM: 1.33Hz 2 Hz
The round panels are centrally loaded by a point load while being supported on three symmetrically placed pivots. The testing arrangement is shown in a sketch in Fig. 36.1. A photo of the rig used in the laboratory at NTNU is shown in Fig. 36.2.
Fig. 36: 1: Recommended testing arrangement ASTM [24]. 2: Testing arrangement used at NTNU.
3: Deflection recorded by use of a laser pointed to a piece of latex fabric.
45 The machine used during the tests was a Dartec RE500 multipurpose testing machine (hydraulic drive) with a maximum load capacity of 500kN. An Instron 8800 controller was used for logging purposes. The load was applied indirectly through a loading piston with a hemispherical end which was displaced at a constant speed.
The displacement of the round panels were not recorded using a LVDT, as indicated in Fig. 36.1.
Instead the displacement was measured with laser equipment, measuring the displacement at the specimen center.
Since the development of cracks could interfere with the laser, a piece of latex fabric was glued to the base of the round panel. In this way the measuring surface was kept flat through the whole laboratory test. The latex fabric is mounted and hit by the laser as shown in Fig. 36.3.
6.7.5 Shear Strength
A total of three beams, cast with the W900 concrete with 0, 0.5% and 1% fiber content, were tested. The purpose for performing the shear beam tests were primarily to test the shear capacity of the W900 concrete with varying steel fiber reinforcement volume.
The shear beams were initially to be run in the end of the same testing period as the rest of the testing done in phase 1. However, a mishap in the laboratory with the rig controller resulted in a delay. An error in the rig controller software, led to unintentional crushing of beam B0 and no data was recorded for this beam. The error was later corrected and the whole testing rig was calibrated and controlled before the two remaining beams were tested. The testing of these two beams was carried out April 21.
6.7.5.1 Loading, Boundary Conditions and Data Logging
The tests were performed using an Alfred J. Amsler & CO. 100kN hydraulic jack together with an Instron 8800 controller for logging purposes. The testing rig is shown in Fig. 37.
Fig. 37: Left: Testing rig used for testing of the shear beams at NTNU. Right: Arrangement of loading and LVDT placement.
6. Test Phase 1: Test Program for Material Data Determination
46
The calculations performed
to 3 should be used in order to assure combinati
A total of 5 LVDT logging purpose
were placed parallel to the longitudinal reinforcement and side of the beam.
the beam center
Fig.
The load level was measured by a load cell in the hydraul displacing
Between the rollers and the concrete specimen, a 10mm thick steel plate an wood fiber plate was placed, in order
the risk of local deformations and unwanted failure. A
boundary condition arrangement can be seen in the test setup for the CSS beams i where a similar test
are summarized in
Table 11: Control parameters used for testing of Control Parameter
Operating Speed Sampling Rate
During testing the beams were inspected constantly in order to determine the crack load. Once the first crack was observed the test was paused and crack bandwidth was re
crack binocular. The load was then applied in adequate intervals in order to record the crack bandwidth an
Test Phase 1: Test Program for Material Data Determination
calculations performed
to 3 should be used in order to assure combination failure. This resulted in load A total of 5 LVDT’s were
logging purposes. The LVTD’s were placed as shown in were placed parallel to the longitudinal reinforcement and side of the beam. Confer
the beam center beneath the beam to measure the vertical displacement
Fig. 38: Sketch of load placing and placing of LVDT's during laboratory testing on shear beams.
The load level was measured by a load cell in the hydraul displacing the specimen at a constant rate,
Between the rollers and the concrete specimen, a 10mm thick steel plate an wood fiber plate was placed, in order
the risk of local deformations and unwanted failure. A
boundary condition arrangement can be seen in the test setup for the CSS beams i a similar test
are summarized in Table
: Control parameters used for testing of Control Parameter
Operating Speed Sampling Rate
During testing the beams were inspected constantly in order to determine the crack load. Once the first crack was observed the test was paused and crack bandwidth was re
crack binocular. The load was then applied in adequate intervals in order to record the crack bandwidth and to draw the crack development.
Test Phase 1: Test Program for Material Data Determination
calculations performed prior to testing to 3 should be used in order to assure
. This resulted in load s were mounted
The LVTD’s were placed as shown in were placed parallel to the longitudinal reinforcement and
Confer Fig. 15
beneath the beam to measure the vertical displacement
: Sketch of load placing and placing of LVDT's during laboratory testing on shear beams.
The load level was measured by a load cell in the hydraul the specimen at a constant rate,
Between the rollers and the concrete specimen, a 10mm thick steel plate an wood fiber plate was placed, in order
the risk of local deformations and unwanted failure. A
boundary condition arrangement can be seen in the test setup for the CSS beams i a similar test arrangement has been used.
Table 11.
: Control parameters used for testing of Control Parameter
Operating Speed
During testing the beams were inspected constantly in order to determine the crack load. Once the first crack was observed the test was paused and crack bandwidth was re
crack binocular. The load was then applied in adequate intervals in order to record the crack d to draw the crack development.
Test Phase 1: Test Program for Material Data Determination
prior to testing
to 3 should be used in order to assure pure shear failure . This resulted in load positions
mounted on the beams during testing The LVTD’s were placed as shown in
were placed parallel to the longitudinal reinforcement and 15 for reinforcement placement.
beneath the beam to measure the vertical displacement
: Sketch of load placing and placing of LVDT's during laboratory testing on shear beams.
The load level was measured by a load cell in the hydraul the specimen at a constant rate,
Between the rollers and the concrete specimen, a 10mm thick steel plate an wood fiber plate was placed, in order to distribute the
the risk of local deformations and unwanted failure. A
boundary condition arrangement can be seen in the test setup for the CSS beams i arrangement has been used.
: Control parameters used for testing of
During testing the beams were inspected constantly in order to determine the crack load. Once the first crack was observed the test was paused and crack bandwidth was re
crack binocular. The load was then applied in adequate intervals in order to record the crack d to draw the crack development.
Test Phase 1: Test Program for Material Data Determination
prior to testing in Section 6.6 pure shear failure
positions as shown in the beams during testing The LVTD’s were placed as shown in
were placed parallel to the longitudinal reinforcement and for reinforcement placement.
beneath the beam to measure the vertical displacement
: Sketch of load placing and placing of LVDT's during laboratory testing on shear beams.
The load level was measured by a load cell in the hydraul
the specimen at a constant rate, using two symmetrically placed steel rollers.
Between the rollers and the concrete specimen, a 10mm thick steel plate an to distribute the load, see
the risk of local deformations and unwanted failure. A
boundary condition arrangement can be seen in the test setup for the CSS beams i arrangement has been used. Control parameters
: Control parameters used for testing of shear beams.
During testing the beams were inspected constantly in order to determine the crack load. Once the first crack was observed the test was paused and crack bandwidth was re
crack binocular. The load was then applied in adequate intervals in order to record the crack d to draw the crack development.
Test Phase 1: Test Program for Material Data Determination
6.6 concluded that a
pure shear failure instead of a flexural tensile failure or a as shown in Fig. 38
the beams during testing for displacement The LVTD’s were placed as shown in Fig. 38. The
were placed parallel to the longitudinal reinforcement and had a matching for reinforcement placement. The vertical LV beneath the beam to measure the vertical displacement
: Sketch of load placing and placing of LVDT's during laboratory testing on shear beams.
The load level was measured by a load cell in the hydraulic jack piston
using two symmetrically placed steel rollers.
Between the rollers and the concrete specimen, a 10mm thick steel plate an
During testing the beams were inspected constantly in order to determine the crack load. Once the first crack was observed the test was paused and crack bandwidth was re
crack binocular. The load was then applied in adequate intervals in order to record the crack concluded that an a/d relation equal instead of a flexural tensile failure or a
38.
for displacement he horizontally placed
a matching pair on the opposite The vertical LVDT was placed beneath the beam to measure the vertical displacement.
: Sketch of load placing and placing of LVDT's during laboratory testing on shear beams.
ic jack piston. The load was applied by using two symmetrically placed steel rollers.
Between the rollers and the concrete specimen, a 10mm thick steel plate and a 10mm thick Fig. 37. This somewhat reduced detailed sketch of the loadin boundary condition arrangement can be seen in the test setup for the CSS beams i
Control parameters used during
Value 2mm/min
1 Hz
During testing the beams were inspected constantly in order to determine the crack load. Once the first crack was observed the test was paused and crack bandwidth was re
crack binocular. The load was then applied in adequate intervals in order to record the crack a/d relation equal instead of a flexural tensile failure or a
for displacement and strain horizontally placed LVDT’s
air on the opposite DT was placed
: Sketch of load placing and placing of LVDT's during laboratory testing on shear beams.
The load was applied by using two symmetrically placed steel rollers.
d a 10mm thick
During testing the beams were inspected constantly in order to determine the crack load. Once the first crack was observed the test was paused and crack bandwidth was recorded using a crack binocular. The load was then applied in adequate intervals in order to record the crack a/d relation equal instead of a flexural tensile failure or a
and strain LVDT’s air on the opposite DT was placed at
The load was applied by using two symmetrically placed steel rollers.
d a 10mm thick This somewhat reduced g and Fig. 86, testing
During testing the beams were inspected constantly in order to determine the crack load. Once corded using a crack binocular. The load was then applied in adequate intervals in order to record the crack
47 At 75-80% of the calculated failure load, recording of the crack development was stopped and the specimen was displaced non-stop until failure occurred. It is assumed in this report that these intermissions did not influence the capacity or behavior of the beam in any negative way.