We were engaged by EMRAIL Sdn Bhd to undertake an investigation into the cause of cracking around the shoulders of pre-cast concrete railway sleepers which became evident during the installation. The sleepers were manufactured as part of a supply contract for the Rawang-Ipoh Electrified Double Track project and there was particular concern for 9,000 sleepers produced between 14th July to 10th August which followed a 1 month plant maintenance shut down at the Mastrack casting yard in Batang Benar, Mantin Negeri Sembilan.
At the time the sleepers were delivered for installation these were in compliance to clause 3.4 of AS 1085.14-2003 which states that the sleepers when removed from the moulds shall be free from cracks, chipped edges, honeycombing and surface defects which lead to inadequate cover. Following installation of the sleepers and prior to full service several of the sleepers were found to exhibit cracking in the vicinity of the sleeper shoulders. The investigation confirmed that the high incidence of defects on sleepers produced during this period was due to the following
It was concluded that the poor shoulder interface characteristics was broken down during the initial installation of the sleepers when a 1 tonne torque was applied to secure the rail position resulting in the characteristic semi-circular hairline concrete separation noted in the sleepers. The spalling at the surface was attributed to poorly formed concrete due to the loss of fine paste through the gaps in the mould during production.
It was recommended that the physically damaged sleepers could be accepted if remedial works are undertaken to the agreed approach and carried out to the required quality under strict supervision. JTK were not involved in overseeing the remedial works.