The bulk density of ordinary concrete is about 23 kN/m3. The concrete having bulk density between 5 to 18 kN/m3 is refer as lightweight concrete and it is prepare from the following materials.

Binding Material ( Lightweight concrete )

The ordinary Portland cement and its varieties can be use as binding material. If local binding material such as lime-slag, lime-cinder, etc. is available, the same can also be adopt as the binding material.

Aggregates

For light-weight concrete, the loose porous materials are use as the aggregates. The natural porous aggregates can be obtain by crushing light-weight rocks. The artificial porous aggregates can be obtain by crushing light-weight rocks. The artificial porous aggregates can be obtain from industrial wastes.

Steel

The light-weight concrete is highly porous and hence it leads to the corrosion of reinforcement, if not property protect. Hence the light-weight concrete should be made adequately dense when use for R.C.C. work. Sometimes the reinforcement is coat with anti-corrosive compounds, when light-weight concrete is adopt.

Water

It is necessary to use pure drinking water to prepare light-weight concrete. The strength of light-weight concrete mainly depends on the amount of water in the mix. The water-cement ratio for achieving optimum strength of light-weight concrete should be carefully work out. As water concrete reaches to its optimum value, there is corresponding increase in the strength of light-weight concrete.

Advantages

• The local industrial waste, if found suitable for light-weight concrete, can be economically utilize.
• Reduction in weight of concrete helps easy removal, transport and erection of pre-cast products.
• The use of light-weight concrete results in the reduction of cost to the extent of about 30 to 40 % or so.
• The light-weight concrete does not present special problems with respect to freezing and thawing. It is due to the fact that the larger pores in aggregate are unlikely to become saturate, provide the cement paste is protect by air entrainment.
• The light-weight concrete has comparatively less tendency to spall. Hence its fire resistance is greater as compare to the ordinary concrete.
• The light-weight concrete has generally a lower thermal expansion than ordinary concrete.
• Sound absorption of light-weight concrete is good because of the fact that the air-borne sound energy is convert into heat in the minute channels of the concrete is nearly twice than that of the ordinary concrete.