Page 18 - Harbour Sludge Stabilisation.pdf

On 23-6-2008 breaking strength tests with 4-points load cell were carried out on test piece 3 of the
ImmoCem 35/3,0 material. Similarly as before the rate of increase of the strain at the bottom of the test
piece of 0.038 MPa per second was applied corresponding to the rate of load increase of 9.94 N per second.
Appendix 5 contains the results of the tests carried out as well as the photograph of the test piece at
failure. The test piece failed at the load of 464 N which resulted in the vertical displacement 0.62 mm.

The calculated stress at failure using equation 4 was 1.77 MPa and the strain at failure (equation 5) was 985
um/m. The stiffness modulus at failure (equation 6) was calculated as 1795 MPa. The observed breaking
tension stress was therefore smaller than that measured for the samples with ImmoCem 35/0,3

However, this time the failure occurred on the top of the test piece in the proximity of 80% of the breadth of
the sample and the failure was more or less horizontal (see appendix 5). This in effect reduced the effective
height of the test piece from 47.07 mm to only 40 mm.

Taking this into consideration and correcting for it results in tension stress at failure of 2.46 MPa and strain
at failure of 837 um/m with the corresponding stiffness modulus of 2940 MPa. These corrected values are
used in determining the test condition for the fatigue tests of the remaining 3 test pieces.

On 23-6-2008 the 1st fatigue test in 4-points load cell was carried out on test piece 2. Rather high tensile
stresses at the bottom of the test piece of 1.8424 MPa have been applied corresponding to 75% of the
measured and corrected tensile stress at failure. Test piece 2 failed rapidly after only 25 load applications
(cycles). The progression of the dynamic stiffness modulus during the fatigue is shown graphically in
appendix 6 as is a photograph of the failure plane of the test piece. It should be noted that a large number
of clean stones in the failure plain have been observed indicating that these were not attached to the binder
and this has obviously contributed to the poor fatigue behaviour of this test piece. The initial stiffness
modulus (at 10th load cycle) was 4530 MPa. This was reduced to 4370 MPa at failure (20th the load cycle).
The initial strain observed 816 um/m and the strain at failure was 841 um/m.

On the 23-6-2008 a 2nd fatigue test in 4-points load cell was carried out on test piece 1. The applied tensile
stress (to the base of the beam) was reduced to 1,23 MPa, 50% of the value for test piece 3. Test piece 1
failed after 59360 load cycles. The progression of the dynamic stiffness modulus S with the cyclic load
application is shown graphically in appendix 7 which also shows a photograph of the failed test piece. The
initial stiffness modulus was 5243 MPa. The stiffness modulus at failure was 3440 MPa. The initial strain was
471 um/m and the strain at failure was observed as 715 um/m.

rd
The 3 fatigue test in 4-points load cell was carried out on test piece 4 was carried out on 24-6-2008. Same
nd
loading conditions as for the 2 fatigue test were used (tensile stress of 1,23 MPa). Test piece 4 failed after
7050 load cycles. The progression of the dynamic stiffness modulus S with the cyclic load application is
shown graphically in appendix 8 which also shows a photograph of the failed test piece. The initial stiffness
modulus was 4016 MPa. The stiffness modulus at failure was 2850 MPa. The initial strain was 611 um/m
and the strain at failure was observed as 858 um/m.

Sample Length, mm Width, mm Height, mm As observed on 8.07.2008
Weight, g Density, kg/m3
2a 159.4 47.40 47.50 501.80 1398
2b 159.3 48.80 47.80 513.1 1404
Table 5. Dimensions and density of the test pieces of beam 2 used for 2 point load cell tests

Following the completion of the fatigue tests with 4 point load cell the pieces of the beams that remained
after the tests were used for the tests with 2 point load cell. These tests were first carried on the remainder
of the test piece number 2 on 24-6-2008. Test pieces with a length of approximately 160 mm were prepared
The edges at which failure occurred in the previous tests were removed in the process. When the samples
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