Are plastic resins being used as grout? If so, isn't this a terribly expensive practice?
Yes. Attempts have been made to apply the new plastics to replace almost every conceivable conventional material. The only record of large-scale use for grouting we have, however, is from Germany where a material known as Polythixon is in widespread use. Expense can apparently be well justified for many jobs because the plastic offers some special properties and advantages over a portland cement grout. The material is supplied in the form of two liquids--the resin and a curing agent--which are site-mixed to give a desired setting time. Both components are oil-based, which means they can not be mixed in water.