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Structural Concrete - Hassoun

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2.17 Lightweight <strong>Concrete</strong> 71<br />

Casting and finishing precast concrete wall panels.<br />

2.17 LIGHTWEIGHT CONCRETE<br />

Lightweight concrete has been made lighter than conventional normal-weight concrete and, consequently,<br />

it has a relatively lower density. Basically, reducing the density requires the inclusion of<br />

air in the concrete composition. This, however, can be achieved in four distinct ways:<br />

1. By omitting the finer sizes from the aggregate grading, thereby creating( what is called no-fines<br />

concrete. It is a mixture of cement, water, and coarse aggregate only 3 − 3 4 8)<br />

, mixed to produce<br />

concrete with many uniformly distributed voids.<br />

2. By replacing the gravel or crushed rock aggregate with a hollow cellular or porous aggregate,<br />

which includes air in the mix. This type is called lightweight aggregate concrete. Lightweight<br />

aggregate may be natural, such as pumice, pozzolans, and volcanic slags; artificial (from<br />

industrial by-products), such as furnace clinker and foamed slag; or industrially produced,<br />

such as perlite, vermiculite, expanded clay, shale, and slate.

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