Chapter 8: Aggregates for concrete

The Standard definition of aggregate is a granular material used in construction; it may be natural, manufactured or recycled. Typically, concrete is comprised of 70% aggregate and the remaining 30% is water, air and cementitious material. However, it is true to say that the fundamental characteristics of concrete are greatly influenced by the physical and chemical properties of the aggregate. There are two factors which determine these characteristics: first, the geological origin and deposition of the material; and second, the physical processing by the aggregate producer. This chapter considers the geological classification of aggregates and the physical and chemical properties resulting from formation and deposition, properties which result from processing into a concrete aggregate and how size, shape, texture, strength and chemical stability impact the properties of concrete and its durability. The chapter also considers lightweight and heavyweight aggregates, both natural and manufactured and recycled aggregates.