Is joint filler essential in concrete expansion joints?

The presence of joint filler is essential to the proper functioning of concrete joints though some may doubt its value. For a concrete expansion joint without any joint filler, there is a high risk of rubbish and dirt intrusion into the joint in the event that the first line of defense i.e. joint sealant fails to reject the entry of these materials. In fact, the occurrence of this is not uncommon because joint sealant from time to time is found to be torn off because of poor workmanship or other reasons. The presence of rubbish or dirt inside the joint is undesirable to the concrete structures as this introduces additional restraint not catered for during design and this might result in inducing excessive stresses to the concrete structure which may fail the structures in the worst scenario. Therefore, joint filler serves the purpose of space occupation so that there is no void space left for their accommodation. To perform its function during the design life, the joint filler should be non-biodegradable and stable during the design life of the structure to enhance its functioning. Moreover, it should be made of materials of high compressibility to avoid the hindrance to the expansion of concrete.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.