The lightweight concrete weight is typically around 115 pounds per cubic foot, compared to the average concrete weight of 145 pounds per cubic foot.
The low weight of the lightweight concrete is due to the use of lightweight fine and coarse aggregate. When the complete aggregate is replaced with lightweight aggregate, the weight reduces the concrete density by approx. 10 pounds per cubic meter.
For example, a concrete slab of 1 square foot of 1.5 inches thick, standard concrete weighs 18 pounds. The same section made of Lightweight Aggregate Concrete weighs approx. 14.5 pounds.
In the construction site, the fresh density of Lightweight concrete is a function of a proportionate mixture of air content, water retention, particle density, and moisture for Lightweight Concrete.
ACI 213 specification of structural grade Lightweight Concrete states that an equilibrium dry density of Lightweight Concrete ranges from between 90 to 115 lb/ft³.
Studies have shown that high quality of Lightweight Concrete absorbs very little water and thus retains its low-density content.
The shape of the aggregates that are used in Lightweight Concrete may have a cubical, rounded, angular, or irregular shape.
Textures of Lightweight Concrete may range from a very fine pore, very smooth skins to very irregular surfaces with large exposed pores.
The shape of the particles and the texture of Lightweight Concrete can directly affect the workability, ratio of coarse to fine aggregate, the cement content requirements, and the demand for water in concrete mixtures.
Compressive strength levels that are commonly required by the construction site for designing of cast-in-place, precast, or prestressed concrete is around 3,000 to 5,000 psi which can be easily obtained with Lightweight Concrete.
The permeability of light-weight concrete was much lower and was generally equal to or significantly lower than reported by standard weight concrete.
Aggregates batched with a high degree of saturation can be replaced by standard weight aggregates to provide internal curing in Lightweight Concrete which contains a high volume of cementitious materials.
The reason is the better hydration of the cement part provided by the moisture found from the slowly released reservoir of water absorbed within the pores of the lightweight aggregates.
The thermal conductivity of concrete depends largely on its density and moisture content but also on the size and distribution of pores, the chemical composition of solid components, and the internal structure of lightweight concrete.
Since light concrete, or lightweight concrete, is relatively low in density and the moisture content is high due to the pores, the thermal conductivity of this concrete is less than that of conventional concrete.
When tested in accordance with ASTM E 119 procedures, structural lightweight concrete slabs, walls, and beams have shown a greater fire tolerance period than members of equal size made of concrete containing standard aggregates.
Lightweight Aggregate Concrete are used as screeds and reinforcement for general purposes especially when screeds or similar thickening and the weight to the floor, roof, and other structural members of the building.
Lightweight Aggregate Concrete is used as Screeds and walls where the timber has to be attached by nailing.
Lightweight Aggregate Concrete is used as casting structural steel to protect against fire and corrosion or as a covering for construction purposes.
Lightweight Aggregate Concrete is used as heat insulation on the roof.
Lightweight Aggregate Concrete is used for insulating the water pipes.
Lightweight Aggregate Concrete is used for the construction of partition walls and panel walls in frame structures.
Lightweight Aggregate Concrete is used for brick fixing to get nails from joinery, especially in the construction of a home or domestic type construction.
Lightweight Aggregate Concrete is used as typical wall insulation.
Lightweight Aggregate Concrete is used for surface rendered for exterior walls of small houses.
Lightweight Aggregate Concrete is also being used for reinforced concrete.
The weight of Lightweight Concrete is 20 to 115 pounds per cubic foot whereas the weight of Conventional Concrete is 130 to 150 pounds per cubic foot.
The compressive strength of Lightweight Concrete is 7000 psi whereas the compressive strength of Conventional Concrete is 8000 psi.
The modulus of Elasticity for Lightweight Concrete is 65000 psi for the ultra lightweight concrete, 3 million psi for the medium-lightweight concrete, where as the modulus of Elasticity is 2 to 6 million psi for the Conventional Concrete.
The shrinkage of the aggregates of light weight concrete are, Perilite 0.1 to 0.2 %, Vermiculite 0.1 to 0.7 %, Slag 0.04 to 0.06 %, Slate and Clay 0.02 to 0.08 %, where as the shrinkage of the aggregates of conventional Concrete is around 0.04 to 0.08 %.
The thermal conductivity of the aggregates of lightweight concrete is Perlite 0.1 to 0.2 %, Vermiculite 0.1 to 0.7 %, Slag 0.04 to 0.06 %, Slate and Clay 0.02 to 0.08 % BTU per hour per square foot per degree F, per inch, whereas the thermal conductivity of the aggregates of conventional Concrete is sand and gravel ranges from 8 to 12 %.
The fire resistance for lightweight Concrete is a 4-hour rating for 4.5-inch slabs with lightweight concrete, whereas the fire resistance is a 3-hour rating for 6-inch slabs made of trap rock, crushed limestone, and gravel aggregates used in conventional Concrete.
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