Buildings constructed from robust materials that can withstand the elements and occupant use for a very long time, are prime candidates for refurbishment and continued service. Buildings constructed using precast concrete fit these criteria. A precast interior frame of a building can have a life expectancy of hundreds of years.
Adaptability is a key factor underlying the ultimate service life of a building. If a building structure is designed so that the interior can be changed without major demolition, the building can have a long life. Long spans, common in precast prestressed structures, are one way of assuring the adaptability of a building. Increasing the load carrying capacity of precast floor systems is not expensive and can extend the useful life of a building by providing flexibility for future conversion to other uses. Secondary installations, such as precast concrete mezzanine floors in industrial buildings, can be installed, or removed, when occupancy requirements demand changes to a building. Precast buildings can also be disassembled and rebuilt at other locations, providing another means of extending the service life. Precast floors and walls can be disassembled from one structure and used to build new structures, providing the same benefits that new precast components offer.
At the end of a building’s useful life, 100% of the precast concrete can be recycled. After removal of the reinforcement, concrete can be crushed to produce aggregates that are primarily used in pavement construction, as granular sub-base, lean-concrete sub-base and soil-cement aggregates. Recycled concrete has also been used on a limited scale as replacement aggregates in new concrete production.
Recycled concrete aggregates have a higher absorption and lower specific gravity than conventional aggregates. Concrete made with recycled coarse aggregates and conventional fine aggregates can obtain adequate compressive strength. The use of recycled fine aggregates can result in minor reduction of compressive strength. The drying shrinkage and creep is up to 100% higher than concrete made with corresponding amounts of conventional aggregates. For these reasons, large scale use of recycled aggregate concrete has not yet been achieved in Canada.
