Like most back-stage technicians, off-camera artists, support staff, Railway Sleepers has never been given its due recognition and importance. Laying on the railway tracks, at the precise gauge positions, one can safely claim that they form the backbone of the railway industry. Choosing the material for railways sleepers is hence of supreme importance. Perhaps, except for the earliest experiments of using stone block sleepers, timber or wood has always dominated the railway sleeper industry. Now, of course with evolving technology, faster train speeds and increased axle loads new materials are being tried and tested. You may want to check out railway sleepers for more.
Wood: There is a reason that wood has been ruling the sleeper industry from the time it was established. Wood is resilient, affordable, available and adaptable. Unfortunately, it is very much prone to wear and tear, the only reason why alternatives are being searched for. Although, the pros outweigh the cons, yet one can always try to look for that perfect material.
Concrete: Gaining ground since the Second World War, these are made from concrete slabs lined internally by steel wires. They are brittle and hence cannot sustain high loads. Pre-stressed concrete of course overcomes this fault, yet the technology and materials used to manufacture it increases the cost, hence it cannot be used for a bulk purpose of constructing railway sleepers. It however would be a good option, if the cost is reduced in the near future.
Steel: Steel sleepers, stronger than timber and cheaper than pre-stressed concrete seemed an ideal solution, unfortunately susceptibility to corrosion, wearing out of rail seats and lack of insulation, and network faults due to high conductivity, steel sleepers provide more problems than advantages. Plastic Composite, many speculate that synthesized plastic could be the future of rail sleepers. Made from recycled raw materials such as plastic, fiberglass, rubber etc, they make an excellent ground for durability and reliability. As technology advances and acceptance increases, they could supersede wood, with the myriad advantages that they have to offer.