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Lightweight aggregate concrete

This forms the bulk of lightweight concrete on site and can be used as a structural material. The density depends on the type of grading of the aggregates used, the moisture content and the mix proportions. The fines can be natural sand or crushed lightweight coarse aggregate. The most commonly used aggregate is LYTAG, a sintered fly ash, also known as pulverised fuel ash (pfa).

Aggregate type Trade name Dry density kg/m3
Furnace clinker
Processed fly ash/pfa Lytag 770-960
Foamed blastfurnace slag
Expanded clay, shale and slate Aglite, Leca, Solite 320-960
Pelletized expanded slag Pellite 800-1000
Wood and plastic particles
Expanded vermiculite

The cellular nature of lightweight aggregates makes them inherently insulating (thermal conductivity coefficient of say 0.09 to 0.16 W/mK compared to 1.15 to 1.44 W/mK for normal concrete). They are also stable at elevated temperatures (except the organic types, e.g. word particles and plastics) and thus have good fire resistance properties.


Lytag aggregate

Acknowledgement: The Concrete Society

Other references:JL Clarke, ´Structural lightweight aggregate concrete´, Blackie Academic and Professional,1993