Light aggregates are used in construction industry to produce concrete with lightweight properties. They are mainly used in structural elements and they are available in different densities.
Lightweight aggregates can be prepared from a variety of materials. In particular, the flue ash from burning coal is utilized as a coarse aggregate. The other types of light aggregates include pumice and vermiculite.
The use of lightweight aggregates in construction has grown rapidly in recent years. However, lightweight aggregates have a number of disadvantages. For example, they are susceptible to freeze/thaw cycles. These factors influence the performance of concrete made with these materials.
A recent research program has compared the performance of two different types of lightweight aggregates in one concrete. This study examined the influence of various saturation levels on the physical and chemical properties of these aggregates.
The results showed that the porous granules of light aggregates had a compressive strength of 1.1-1.7 MPa in a cylinder. They also had a higher mechanical strength than other light aggregates.
The performance of lightweight aggregates was assessed through a compaction factor test and a rebound hammer compressive strength. It was found that the porous granules had a higher water-cement ratio than the other aggregates. Besides, the weight of the aggregate decreased to a level of 300-420 kg / m3.
The granules are produced by grinding the igneous rock screenings. They are then dried and calcined.
The granules are sintered at high temperatures in a rotary kiln. The sintering process is designed to produce a coating that is less porous than the internal structure of the aggregate.