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Testing of concrete sleepers
In addition to the control checks exercised on the material and manufacturing process, the concrete and the finished sleepers are subjected to the following periodical checks and tests.
(a) The minimum 28-day compressive strength of the test cube should not be less than 525 kg/cm2. Sleepers from occasional batches in which the minimum crushing strength falls below 525 kg/cm2 but not below 490 kg/cm2 may be accepted subject to their passing the increased frequency of testing for static bending strength.
(b) The minimum compressive strength of the test cube of concrete at detensioning should not be less than 370 kg/cm2.
(c) The modulus of rupture should be as specified in the Concrete Bridge Code.
(d) The dimensional tolerance and surface finish of the sleepers should be checked using suitable templates and gauges.
(e) The cracking and failure moments of the sleepers should be tested at the following sections by applying suitable loads:
(a) Positive cracking moment at rail seat bottom
(b) Negative cracking moment at centre section top
(c) Positive cracking moment at centre section bottom
(d) Failure moment at rail seat bottom
(f) For the abrasion resistance test, the concrete sleeper is subjected to a vibrating load under specified conditions. After 300 hours of operating time, the loss in weight due to abrasion should not be more than 3%.
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