Particle Shape of Crushed Concrete

Aggregate particle shape affects many concrete properties, including shear strength and permeability. This article reports on a study of the impact of particle shape of crushed concrete, such as that obtained from construction and demolition waste. Two types of crushed concrete were tested: Material A from the demolition of old City Hall in Sheffield, United Kingdom; Material B from a demolition waste processor (Sam Allon, Ltd) in Hull, United Kingdom. Material A contained impurities such as glass, plastic, steel, copper, wood, ceramic, adhesive, lightweight concrete, and plaster; material B had impurities including glass, wood, and copper. The authors describe the study methods, then consider three-dimensional particle shape, and flakiness and elongation indexes. A final section considers the Lees method of shape classification. The authors conclude that, because their study was part of a larger project to examine the properties of crushed concrete to be used as aggregates, they did not have enough time to study the shape properties. A larger number of particles are needed to be studied to collect more data and obtain a better overall picture of the shape characteristics. Using different methods for examining the particle shape for all size fractions could be useful for providing the ability to compare crushed concrete shape characteristics with a wider range of materials.