28-08-2013, 03:22 PM
CONSTRUCTION OF PREFABRICATED BUILDING COMPONENTS USING FLY ASH
CONSTRUCTION OF PREFABRICATED.pdf (Size: 355.45 KB / Downloads: 122)
ABSTRACT:
In today’s world, where speed and convenience play a big part in
influencing the use of any product, the age of prefabricated housing products
seems to have finally arrived. The usefulness of these products help significantly in
speeding up construction by offering ready-to-install building elements such as
blocks, joist beams, roof blocks and panels is being widely recognised in the
industry. Pre-fabricated components are becoming immensely popular due to the
several attractive advantages that they offer, such as off-site fabrication, which
allows reduction in construction time and this function helps greatly in managing
the schedule of the construction project. Due to their low density, the pre-
fabricated components impose a relatively lighter load on the structure and
superior quality can also be achieved as these components are manufactured
under a strictly controlled environment. In recent times few innovations in the
field of materials are expected to make these products even more popular, user
friendly and eco friendly. The present paper discusses on the manufacturing of
prefabricated building components using fly ash, and explains regarding
fabrication, centring, placing, applications and the advantages over the monolithic
construction.
INTRODUCTION:
Prefabrication:
“Prefabrication” is the manufacture of an entire building or components cast in a
factory or on site before being placed in position, assembling the structural units so that
they can be easily and rapidly erected. Prefabricated buildings are pre-cut, pre-drilled,
and pre-engineered before the actual building is constructed. Prefabricated Structures
(PFS) are useful for sites, which are not suitable for normal construction methods such
as hilly regions, and also when normal construction materials are not easily available.
Structures which are used repeatedly and can be standardized such as mass housing,
storage sheds, godowns, shelters, bus stands, security cabins, site offices, foot over
bridges, road bridges, concrete building blocks etc., are prefabricated structures. This
paper discussing about the mix proportions f the materials to manufacture the prefab
components and the construction procedure for an ordinary single story residential
building.
Chemical Properties:
In Indian fly ashes, contents of SiO2, Al2O3 are relatively higher than Fe2O3,
SO3. The crystalline phases were identified as mullite, magnetite, hematite and quartz.
The chemical composition of fly ash and its particle size differ widely for different
power plants. This is due to different types of coal used, their various treatment and
different types adopted for combustion. Generally, fly ash is differentiated on the basis
of degree of fineness and their carbon contents.
Thin Precast RCC Lintel:
Normally lintels are designed on the assumption that the load from a triangular
portion of the masonry above, acts on the lintel. Bending moment will be WL/8 where
W is the load on the lintel and L is the span assumed for the design purpose. By this
method, a thickness of 15 cm is required. Thin precast RCC lintels are designed taking
into account the composite action of the lintel with the brickwork. The thickness of the
lintel is kept equal to the thickness of brick itself having a bearing of 230 mm on either
supports. Use of precast lintels speeds up the construction of walls besides eliminating
shuttering and centreing. Adoption of thin lintels results in up to 50% saving in
materials and overall cost of lintels.
WHY SHOULD WE PREFER PREFABRICATION?
In India, adoption of prefabrication building techniques has many merits, like
availability of materials, labour, and technical skills. Advantages of prefabrication are
multiple as the components are readymade and self-supporting, shuttering and
scaffolding is eliminated, with a saving in shuttering cost. In traditional construction,
the repetitive use of shuttering is limited, as it gets damaged due to frequent cutting,
nailing, etc. On the other hand, the mould for the precast components can be used for a
large number of repetitions, thereby reducing the cost of the mould per unit. In the
prefabricated housing system, there is saving of time, as the elements can be cast
beforehand during the course of the foundation being laid. Even after laying slab, the
finishes and services can be done below the slab immediately.
CONCLUSIONS:
Mass housing targets can be achieved by replacing the conventional methods of
planning and executing building operation based on special and individual needs and
accepting common denominator based on surveys, population needs and rational use of
materials and resources. No single approach and solution is available which can satisfy
the community at large. However, what is ideal and desirable is to have a system, which
can provide choice for people and also appropriate techniques to meet the situation. The
essence lies in the system approach in building methodology and not necessarily
particular construction type or design. Adoption of any alternative technology on large
scale needs a guaranteed market to function and this cannot be established unless the
product is effective and economical. Partial prefabrication is an approach towards the
above operation under controlled conditions.