Light weight concrete

Lightweight Concrete

Concrete with porous aggregates is now the most commonly used types of lightweight concrete. Its density does not exceed 180 kN/m3 because of the use of light and porous aggregate. The light cocnrete not only result in saving the dead weight of the structure but has better insulation against heat and sound. The strength of such concrete is, however, less, but still, it is adequate to be used for precast concrete and reinforced concrete units.

Lightweight aggregate is relatively new material. For the same crushing strength, the density of concrete made with such an aggregate can be as much as 35% lower than the normal weight concrete. In addition to the reduced dead weight, the lower modulus of elasticity and adequate ductility of lightweight cocnrete may be advantageous in the seismic design of structures. Other advantages of this material are its greater fire resistance, low thermal conductivity, low coefficient of thermal expansion, and lower erection and transports costs for pre-fabricated members. For pre-fabricated structures, a smaller crane is required or the same crane can handle larger units due to a reduction in dead weight. For cost in-situ structures, its sample dead weight makes foundations less expensive.

Ordinary lightweight cocnrete prepared from a binder, water fine and coarse aggregate with full filling voids between the large particles.
Low Sand concrete, in which the voids between the coarse aggregate are only partially filled with the paste. It is also called a gap graded concrete and dealt separately.
In this case on fine aggregate is used. Coarse particles of the aggregate are coved by a thin layer of cement, paste and the voids between them remain empty. It is called as no concrete.
Aerated cocnrete made from a binder, water, fine and coarse aggregate, and a blowing agent which decreased the density of concrete.

Properties of lightweight concrete

Low Density
Fire Resistance
Sound Insulation
Durability
Thermal insulation
Quality Control

Low Density

The density of concrete varies from 300 to 1200 kg/m3 The lightest grade is suited for insulation proposed while the heavier grades with adequate strength are suited for structural applications. The low density of cellular concrete makes it suitable for precast floor and roofing units which are easy to handle and transport from the factory to the sites.

Fire Resistance

Lightweight concrete has excellent fire resisting property. its low thermal conductivity makes it suitable for protecting another structured form the effects of fir

Sound Insulation

Sound insulation in cellular concrete is normally not as good as in dense concrete.

Durability

Aerated concrete is only slightly alkaline. Due to its porosity and low alkalinity, it does not give rust protection to steel which is provided by dense compared concrete.

Thermal insulation

The insulation value of lightweight concrete is about three to six, times that of bricks and about ten times of cocnrete. A 200 mm thick wall of aerated cocnrete of density 800 kg/m3 has the same degree of insulation as a 400 mm thick wall of density 1600 kg/m3.

Quality Control

Better quality control is exercised in the construction of a structure with lightweight concrete products owing to the use of factory made units.

Light weight concrete