This was a final year undergraduate civil engineering degree project which undertook testing to determine the remaining strength in old railway sleepers. Testing was done on concrete compressive strength and static bending test.

1. Testing of 50
year old
prestressed
concrete railway
sleepers
Daniel Dwyer
June, 2016

2. What are they?
 12 x narrow gauge sugar
cane railway sleepers
 Length = 1220 mm
Mass = 40 kg

3. What did we do?
1. Tested the concrete
compressive strength
Using a Schmidt hammer

4. 2. Tested the sleepers in
static bending
Displacement control test
Loading rate = 0.5 mm per minute

5. What did we aim to find?
 How much strength remained in the aged sleepers?
 Could they be safely put back into service?
 What was the concrete compressive strength after 50
years in service?
 What can we interpret from these findings in relation
to concrete structures in general?

6. How did we structure the test?
 Categorised the sleepers into three groups
Bad, Average and Good
Based on visual assessment
 Marked the sleepers at specified locations
1 2 3 4 5 6 7
G stands for Good

7. The marked sleepers provided…
 Consistent Schmidt hammer test point locations
&
 Reference points to monitor cracking during static
bending tests
345

8. What did we find?
 The compressive strength was highest at the rail seat
locations and visual assessment did prove to be an
effective method for the top of sleeper
25
30
35
40
45
50
55
60
65
0 1 2 3 4 5 6 7
Strength
(MPa)
Point number
Top of sleeper compressive strengths
Good
Average
Bad
Design strength

9.  It was believed that the rails had protected the top
concrete surface from environmental exposure which
helped maintained strength

10.  The compressive strength was considerably lower for
the side of sleeper
25
30
35
40
45
50
55
60
65
0 1 2 3 4 5 6 7
Strength
(MPa)
Point number
Side of sleeper compressive strengths
Good
Average
Bad
Design strength

11.  Static bending test results were not predictable from
the visual assessment method
0
10
20
30
40
50
60
70
80
0 300 600 900 1200 1500 1800 2100
Load(kN)
Time (s)
BA
BB
AA
AB
GB
GD

12.  However, all sleepers easily exceeded the proof
bending test requirement of,
“no cracking visible to the naked eye at 32.5 kN”
Sleeper code Cracking load (kN) Ultimate load (kN)
BA 72 73.1
BB 61 61.2
AA 52 53.4
AB 60 61.9
GB 65 65.7
GD 72 72.8
Bad
Average
Good

13. 0
10
20
30
40
50
60
70
80
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Load(kN)
Deflection (mm)
BA
BB
AA
AB
GB
GD

14. Sleeper AB failure video

15. How did they fail?
 All sleepers exhibited the same failure method -
believed to be shear
Diagonal cracking
initiated at the
bottom

16.  Although cracking did not initiate at the supports,
there was no sign of flexural cracking at the centre
span
Flexural cracking was
not present
There was only one
major crack in
each specimen

17. What did we learn?
 The prestressing strands were
still in very good condition
visually but were not tested

18.  Even after 50 years, the sleepers’ strength was high
 They could potentially be put back into service safely