ABSTRACT
Recycling of elements of concrete structures at the end of their working life as components of new structures is difficult, with the exception perhaps of some pre-cast elements. Concrete is produced to order for specific applications and there is considerable economic incentive to avoid waste, e.g. by not over-ordering from ready-mixed concrete suppliers. Freshly mixed cement and concrete is alkaline and the waste is therefore classed as hazardous. After demolition, the large lumps of concrete are fed through a crushing machine, the steel reinforcement and timber etc. are removed and the resulting particles then passed through screens to divide them into size fractions, as for primary aggregates. The majority are then used as hardcore for foundations, sub-base for roads pavements and other fill applications, but an increasing amount is used in new concrete. Recycled aggregate has been shown to be suitable for low-strength concrete blocks, but recycled concrete aggregate can be used in structural strength concrete.
