13-09-2014, 11:41 AM
Structural Lightweight Concrete
Lightweight Concrete.ppt (Size: 1.29 MB / Downloads: 17)
Introduction
Lightweight concrete can be defined as a type a type of concrete which includes an expanding agent in that it increases the volume of the mixture while giving additional qualities and lessened the dead weight.
It is lighter than the conventional concrete.
The use of lightweight concrete has been widely spread across countries such as USA, United Kingdom and Sweden
Compressive Strength
Compressive strength is the primary physical property of concrete and is the one most used in design.
Fourteen trial mixes had been prepared
during the research and from the results, the mixture with the highest compressive strength was used.
Water Absorption
Water absorption is an important factor due to the porous structure of the aerated
lightweight concrete.
The water absorption test is done using the samples prepared at the age of 28 days.
The purpose of this test is to identify the capability of the concrete to absorb water
Entrained Air
As with normal-weight concrete, entrained air in structural lightweight concrete ensures resistance to freezing and thawing and to deicer applications.
It also improves workability, reduces bleeding and segregation, and may compensate
for minor grading deficiencies in the aggregate.
SLUMP
Due to lower aggregate density, structural lightweight concrete does not slump as much as normal-weight concrete with the same workability.
It is seldom necessary to exceed slumps of 125 mm (5 in.) for normal placement of structural lightweight concrete.
VIBRATION
As with normal-weight concrete, vibration can be used effectively to consolidate lightweight concrete; the same frequencies commonly used for normal-density concrete
are recommended.
Excessive vibration causes segregation by forcing large aggregate particles to the surface.
APPLICATIONS
Lightweight concrete has been used since the eighteen centuries by the Romans.
The lightweight concrete was also used in
construction during the First World War. The United States used mainly for shipbuilding.
It is widely used as loose-fill insulation in masonry construction where it enhances fire
ratings, reduces noise transmission, does not rot and termite resistant.
FACTORS FAVOURING
Poor foundation condition.
Severe earthquake forces.
Durability.
Rapid construction.
Space utilization.
Reduced site work.
Innovative spirit
DESIGN
The use of lightweight concrete was initially proposed by Stresscrete, the precast concrete supplier.
But it was also readily accepted by the project structural consultants, Holmes Consulting Group, who were impressed by the potential of the product to reduce cost and responded enthusiastically to the challenge of a new material.
CONCLUSION
The initial findings have shown that the lightweight concrete has a desirable strength to be an alternative construction material for the industrialized building system.
The strength of aerated lightweight concrete are low for lower density mixture. This resulted in the increment of voids throughout the sample caused by the foamThe foamed lightweight concrete is not suitable to be used as non-load bearing as the compressive strength is 27% less than recommended. The compressive strength is accepted to be produced as non-load bearing structure.