Recycling of demolished masonry rubble.

The recycling of demolished masonry rubble as the coarse aggregate in new concreterepresents an interesting possibility at a time when the cost of dumping such materialis on the increase. With growing concerns over the environmental impact of aggregateextraction and the continued rise in aggregate demand in the UK, it is clear that themarket is now there for recycled and secondary aggregates.The present investigation consists of experimental and theoretical studies into theeffects of using recycled aggregates to produce concrete instead of virgin aggregates.The aggregates used have been recycled from construction and demolition waste. Therecycled aggregates were predominately made up of crushed bricks but the aggregatesdid contain impurities such as timber and mortar. New bricks were crushed to forman aggregate in order to investigate the properties of brick as a material withoutimpurities. The physical properties of the various aggregates were firstly examined and comparedwith granite aggregate, an aggregate proven in the production of good qualityconcrete. Concrete was then produced with the aggregates and all the physical andmechanical properties of the concretes were examined in some detail. The resultsshowed that recycled masonry aggregates can be used successfully to produce·concrete of an acceptable standard.New test methods were presented in this investigation to determine brick porosity andwater absorption. This involved the testing of broken brick fragments under vacuum,rather than the testing of whole brick units by 5hrs boiling or 24hrs submersion incold water. The new test methods proved to be easy to perform and provided accurateresults.A new test method for estimating the strength of bricks was presented. This involvedpoint-loading of masonry specimens to obtain strength index values. From the pointloadresults, equations were presented relating the strength index values of brickfragments to the compressive strength of whole brick units. This involved the development of shape factors for different masonry specimens. The point-load test iseasy to perform, presents a cheaper alternative to heavy compression machines andcan be used on site to determine the suitability of recycled bricks as the aggregate innew concrete