Pozzolanic reactivity of lightweight aggregates

Over recent years more attention has been given to the influence of the aggregate-cement paste interfacial zone on the various properties of concrete. For the lightweight aggregate - cement paste interface, it is believed that the interface is characterized by a mechanical interlocking in combination with a chemical interaction in the form of pozzolanic reaction. In the literature, however, not too much information on the effect of the pozzolanic reactivity of lightweight aggregates is available. Therefore, an investigation on the pozzolanic reactivity of some lightweight aggregates based on expanded clay and sintered fly ash was carried out. A certain degree of pozzolanic reaction between cement paste and lightweight aggregate was observed, but the effect was not very pronounced. The low degree of pozzolanic reactivity may be the result of a recrystallization of the mineral compounds during the manufacturing process of the aggregate.