Physical and Chemical Characteristics of Aggregates

Aggregate is a granular material that generally occupies 70 to 80% of the volume of concrete. In addition to being an economical filler, aggregate also plays an important role in controlling several properties of concrete including mixture composition, dimensional stability, wear resistance and durability.

Although aggregates are typically assumed to be chemically inactive, in some cases they can contribute to degradation of concrete, especially if they contain such substances as chlorides, sulfates, alkali-reactive silica, or clay and organic particles. In addition, some aggregates may show poor freeze-thaw resistance, especially if they contain absorbent components such chert, shale or some porous limestone.

The course will cover the physical and chemical aspects of the durability of aggregates and explore how these characteristics influence the performance of concrete. In addition to covering the “ordinary” aggregates, the course will also explore the properties and uses of recycled concrete aggregates as well as aggregates for “specialty” concretes, including radiation shielding, ultra-high strength, lightweight and internally cured materials.