SPEEDY CONSTRUCTION LIFT SLAB CONSTRUCTION READY MIX CONCRETE CROSS WALL AND BOX FRAME REINFORCEMENT FORMWORK

1. SPEEDY CONSTRUCTION
QUES-1) WHAT DO YOU UNDERSTAND BY SPEEDY CONSTRUCTION?
Ans-1) SPEEDY CONSTRUCTION:
In general concrete construction, we have seen that whatever the elements cast (beams, columns, slabs
etc.) Require time for setting. This is a long drawn process necessary for hardening of concrete.
However, nowadays in large scale projects, newer methods of faster construction are being explored.
Fast and efficient construction of the concrete core of a building is essential to maintain phased
progress on other parts of the building. Formwork is one of the most important factors in determining
the success of a construction project in terms of speed, quality cost and safety of work as it accounts
about 40% of the total project cost of the structure. To minimize the costs the contractor needs to
complete the project as soon as possible and the client wants the building to use the building as early as
possible for the intended purpose. In building construction the most efficient way to speed up the work
is by achieving a very short floor cycle. That directly depends on the selected form work type for the
construction.
Some of the methods to provide speedy construction are:
• Members are cast on ground and then lifted to save on the time and money used for
shuttering. Ex: lift slab construction
• Precast concrete blocks are used.
• Such members are used which do not require elaborate formwork. Ex: flat slab
• Ready mix concrete (rmc)
1) LIFT SLAB CONSTRUCTION :
Lift slab construction is a method of constructing concrete buildings by casting the floor or roof slab on
top of the previous slab and then raising the slab up with hydraulic jacks, so being cheaper and faster as
it does not need forms & shores as it is needed for cast-in-place slabs. Lift-slab construction can be
more economic than conventional construction when the building is vertically uniform, such as for
hotels, apartment buildings, and dormitories, and where the slab designs are repetitive.
After the slabs have cured long enough to reach a prescribed strength, powerful hydraulic jacks
mounted on top of the columns lift the slabs into their respective positions. A console connected to
each hydraulic jack synchronizes the number of turns of the check nuts to assure that the concrete slab
is being raised the same amount at all points.
 Lift slab can be used for heights up to about 16 stories.
 Economical column spacing ranges from 22 to 32 feet.
 Columns may be pipe, tubes or wide flange sections; concrete columns may be used in 3- to 4-
story buildings.

2. ADVANTAGES OF LIFT SLAB CONSTRUCTION:
 Lift-slab construction method becomes more advantageous in buildings with similar floor plans
throughout the height of the building and where flush slab may be desired.
 This method eliminates the need for redundant formwork as only shuttering required on the
edges, therefore casting concrete slabs is the simplest stage in whole constriction process of lift-
slab method.
 Lift-slab method may be employed with ribbed slabs not only flat slabs with some compromise
of the ease of casting.
 Another advantage is reduced handling and hoisting of materials and supplies that can simply be
placed on top of the slabs and lifted with them.
MAJOR LIMITATIONS OF LIFT SLAB CONSTRUCTION:
 This method not to be use for multistorey building, only use for 15- 16 storey building.
 No large span slab are constructed in this type of construction.
2) READY MIXED CONCRETE:
Ready mixed concrete, or rmc as it is popularly called, refers to concrete that is specifically
manufactured for delivery to the customer's construction site in a freshly mixed and plastic or
unhardened state.
Concrete itself is a mixture of portland cement, water and aggregates comprising sand and gravel or
crushed stone. In traditional work sites, each of these materials is procured separately and mixed in
specified proportions at site to make concrete. Ready mixed concrete is bought and sold by volume -
usually expressed in cubic meters.
Rmc can be custom-made to suit different applications
ADVANTAGES OF RMC:
Ready mixed concrete is manufactured under computer-controlled operations and transported and
placed at site using sophisticated equipment and methods. Rmc assures its customers numerous
benefits:
 Uniform, consistent and assured quality of concrete
 Flexibility in concrete design mixes
 Easier addition of admixtures
 Faster and speedier construction
 Reduced inventories, material handling and storage of raw materials at sites
 Savings in labour requirements, labour costs and supervision of labour
 Reduced wastage of materials

3. QUES-2) WHAT IS IN-CAST SITU CONSTRUCTION? DEFINE CROSS WALL AND BOX WALL WITH SKETCHES.
ANS-2) CAST-IN SITU CONSTRUCTION:
The cast-in-situ concrete is standard concrete which is poured into the specific formwork on the site and cured to
get the strength of RCC elements. In-situ is most commonly a mixture of aggregate (known as builder's mix)
blended with portland cement and clean water, that is free of oils, acid and others. In situ techniques are often
more labour-intensive, and take longer, but the materials are cheaper, and the work is versatile and adaptable.
 Column, slab etc. elements are cast on site and hence it is difficult to control mix, placement and curing in
cast-in-situ concrete.
 More labours are required.
 In situ concrete construction is slow as gaining of strength requires time.
 Weather condition can delay the casting work.
 In situ concrete is a cheaper form of construction for small structures.
 Less maintenance cost.
 More resistant to earthquake and wind forces.
CROSS WALL & BOX WALL :
•In Box Frame construction, the walls and slabs are cast monolithically in the form of boxes with the open ends
of the boxes as cladded main external walls.
•The lateral front and rear walls do not participate in the load bearing structure.
•The load of floors and slabs are carried by internal walls perpendicular to the principal axis of building called as
Cross walls and hence also called as Cross Wall Construction.
Origin of Cross Wall Construction : In traditional buildings, the timber joists were arranged in the direction of
shorter spans and were often supported on cross walls or partition walls rather than columns or lateral external
walls.
MERITS OF CROSS WALL CONSTRUCTION:
 Structural & non-structural elements can be standardized and can be fabricated, resulting in speeding up
of erection.
 The cross- walls result in economy of labor, material and space.
 The cross wall being internal are not affected by weather provided the designed thickness affords a
reasonable standard of sound insulation, no additional thickness is called for, as the problem of rain
penetration does not rise.
DEMERITS OF CROSS WALL CONSTRUCTION:
 The limitation of planning which results when the cross walls are maintained at maximum intervals of
about 5.5m.
 It is clear that a building would be structurally unsound if it consisted of a number of detached cross walls
extending through several storeys without lateral or longitudinal ties or supports, especially when the
cladding is the light weight type.
 Renovation work is most difficult in such construction.
 Doors need to come in the middle third of the wall. cross wall

4. ECONOMIC ACHIEVEMENT IN BOX FRAME CONSTRUCTION :
•As lateral external walls are non-load bearing, so, In contemporary cross wall construction, the external walls
are of relatively light cladded construction, which is resistant to rain transmission and is adequately insulated
•Maximum economy is achieved if cross walls are properly planned to be same distance apart through out the
length of the building. this results in :
 Standardization of certain elements.
 Panels of light weight cladding.
 R.C.C. concrete floor having same imposed load.
 Form work can be used again and again.
 Erection is expedited.
USES:
 These are used in buildings where floor plans are typical like hospitals, hotels etc.
 This type of construction is most suited to building types that are upto 5 storeys high.
 The spacing of cross walls varies from 3-5.5 m
 Used at the site where speedy construction is done.
POINTS TO TAKE CARE WHILE CONSTRUCTING CROSS WALL :
 Care must be taken to ensure that the end of the cross walls are sealed to prevent the admission of rain.
 The damp proofing of the cross wall is done with a fibrous asphalt felt or D.P.C.
 To prevent the admission of rain through any defective joints in the terracotta facing, the end of the wall
may be given two good coats of bituminous paint or other water repellent emulsion cross wall.

5. QUES-3) WHAT IS THE REINFORCEMENT AND WHAT ARE THE TYPE OF REINFORCEMENT AND THEIR USES?
EXPLAIN WITH SKETCHES.
ANS-3) Concrete is very high in compressive strength, but it is low in tensile strength. Thus, when only the
compressive loads are acting on the concrete surface then there is no need of using reinforcement in it. But
where tensile forces are also involved, as in, beams and slabs, there is a very risk of its failure when plain concrete
is used. Steel, however, as we know, has a very high tensile strength (and also as high compressive strength.
Hence when the two (concrete and steel) are combined together, a material of construction is obtained that is
capable of withstanding all the three types of forces likely to act upon a structure: compressive loads, tensile
stresses, and shear forces Such a material is known as Reinforced Cement Concrete.
There are mainly 4 types of steel reinforcement used in concrete structures:
1. HOT ROLLED DEFORMED BARS:
This is the most common type of reinforcement for regular RCC structures. Hot rolling is done in the mills which
involves giving it deformations on the surface i.e. ribs so that it can form bond with concrete. The stress - strain
curve shows a distinct yield point followed by a plastic stage in which strain increases without increase in stress.
This is followed by a strain hardening stage. It has typical tensile yield strength of 60,000 psi.
2. MILD STEEL PLAIN BARS:
These are plain bars and have no ribs on them. These are used in small projects where economy is the real
concern. As plain bars cannot bind very well with concrete hence hooks have to be provided at the ends. In this
type of steel too stress - strain curve shows a distinct yield point followed by a plastic stage in which strain
increases without increase in stress. This is followed by a strain hardening stage. Plastic stage in Mild Steel Bars is
even more pronounced than Hot Rolled Deformed Bars. Typical tensile yield strength is 40,000 psi.
3. COLD WORKED STEEL REINFORCEMENT:
When hot rolled steel bar undergoes process of cold working, Cold worked reinforcement is produced. Cold
working involves twisting or drawing the bars at room temperature. This effectively eliminates the Plastic Stage in
the Stress-Strain curve, although it gives more control over the size and tolerances of bars. Due to removal of
plastic stage it has lower ductility than Hot Rolled bars. Its use is specific to projects where low tolerances and
straightness are a major concern. The stress – strain curve does not show a distinct yield point as plastic stage is
entirely eliminated. Yield point is determined by drawing a line parallel to the Tangent Modulus at 0.2% strain.
Yield stress is the point where this line intersects the stress – strain curve. This is known as 0.2% proof stress. If
yield stress is determined at 0.1% strain it is called 0.1% proof stress. Typical tensile yield strength is 60,000 psi.
4. PRESTRESSING STEEL:
Prestressing steel is used in the form of bars or tendons which are made up of multiple strands, however,
tendons / strands are more frequently used as these can be laid in various profiles, which is a primary
requirement of prestressing steel. Prestressing strands are, in turn, made up of multiple wires (typical 2, 3 or 7
wire strands). Typical seven wire strand consists of six wires spun around the seventh wire which has a slightly
larger diameter, thus forming a helical strand. These wires are cold drawn and have very high tensile ultimate
strength (typically 250,000 - 270,000 psi). Their high tensile strength makes it possible to effectively prestress
concrete even after undergoing short term and long term losses. These are used in prestressed concrete in
bridges or prestressed slabs in buildings. Prestressing steel is also available as non-bonded strands encased in PVC

6. sheath. It is used in Post-Tensioning of members. Prestressing strands are also available as Low Relaxation
Strands which exhibit low relaxation losses after prestressing. These are typically used in prestressing members
with large spans.
QUES-4) HOW READY MIX CONCRETE IS DIFFERENT FROM THE CONCRETE PREPARED AT SITE?
ANS-4) Ready mixed concrete is certainly an advancement over the age-old site mixed concrete. The benefits of
RMC in terms of quality, speed, life-cycle cost and environmental friendliness are overwhelmingly superior to
those of site mixed concrete. Following brief comparison illustrates this vividly:
Factors Hand/Manual/Site Mix Ready Mix Concrete
Concrete
Consistency
Fairly difficult to achieve consistency since it is
manually mixed at the site.
Concrete mortar is consistent since it is
computerized machine produced.
Manpower
Requirement
Requires more labor force both skilled and unskilled
for mixing the mortar and shifting it, laying and
compacting.
Skilled labor required only to lay and compact the
concrete as per the design.
Concrete Mortar
Mix Ratio
Respective structural Engineer/ Architect will
provide the details of Concrete Grade whether it is
M20, M25, M30 etc. and the thickness of the
concrete mould.
Respective structural Engineer/ Architect will
provide the details of Concrete Grade whether it is
M20, M25, M30 etc.. and the thickness of the
concrete mould.
Material
Management
Requires proper estimation the material sand
availability at the site ahead of schedule.
Material procurement not a concern but proper
concrete estimation needs to do.
However, the RMC agency should confirm the
materials used in the mortar which may include Fly
ash, GGBS, Chemicals etc..
Time Spent
Requires approximately 50% more time compared
to RMC.
Requires approximately 50% less time compared to
Site Mix.
Site Condition
Requires enough space to accommodate materials
and site mix machinery.
Requires a road width of minimum 30 feet for
smooth maneuvering of the RMC carrier vehicle.
Quality
Monitoring the concrete mortar mix ratio through
the process is critical.
Owner should obtain the cube test report from the
RMC Company.
Quality control on
Raw Materials
Quality consistent materials is very critical to
achieve the concrete compression strength
required.
Choose certified RMC suppliers who manufacture
according to IS standards and will provide cube test
reports.
Laboratory test
results for
concrete
Normally not tested for site mixes. The owner can
opt for cube testing by any third party testing
laboratories.
Testing to be done by RMC manufacturer and no
additional charges are levied.
Pricing
Site mix is generally cost effective compared to
RMC.
RMC is costlier compared to site mix but it is very
convenient.
QUES-5) WHAT IS THE ROLE OF FORMWORK IN SPEEDY CONSTRUCTION? DEFINE ITS TYPES.
ANS-5) The use of formwork is so important in the process of construction. This is an impermanent or stable
molding into which concretes are poured. The use of formwork is assisted with scaffolding in order to support it.
This is used to provide the exact formation to a building; hence, this should be made with caution and should be
done only by professional formwork contractors. The following are the key reasons why formwork is highly
important for any project -

7. 1. Time Management - Good formwork systems help to minimize floor to floor construction cycle time, thereby
achieving substantial indirect cost saving for the project.
2. Safety - Modern formwork systems provide designed solutions against all superimposed loads thereby
ensuring structural safety. Also they integrate proper access and working platform arrangements in the scheme
to ensure workmen safety.
3. Quality - Surface finishing of any concrete is solely contributed by quality & type of formwork used. Superior
surface finish imparted by Aluminium formwork, Tunnel form eliminates the need of plastering for any RCC
surface.
4. Project Planning - Proper knowledge of formwork management facilitates on-time mobilization &
demobilization of formwork resources, effective set movements, minimize idling, maximize repetitions and
minimize cost. It also helps in correct time & cost inputs for tendering process.
5. Human Resource - Formwork activities requires specialized skill sets for all levels of personnel involved. Hence
proper skill assessment, training & effectiveness tracking are continual mandatory needs to maximize labour
productivity.
6. Capital Management - Substantial quantum of Formwork materials owned by any construction company fall
under asset category and travels from one project to the next. Hence accounting, physical verification, loss
mitigation needs to be practiced meticulously to avoid unnecessary substantial cost impacts.
TYPES OF FORMWORK:
1) Conventional Type of Formwork: This is the most traditional type of formwork and this uses timber, bamboo,
masonry and carpentry to complete construction. Low initial cost, low experience factor and low weight are some
of the advantages while high floor cycle, poor finish, and high labor requirement are the disadvantages of this
formwork type. This formwork type is still in practice in two – three storey building construction projects.
2) Fiberglass formwork: The use of fiberglass as a material to make forms for concrete work has increased rapidly
within the past two years. Among the reasons are:
– Fiberglass forms provide a means of producing a concrete surface that is architecturally
acceptable without rubbing and grinding.
– Special patterns and designs can be readily molded into the material.
– Large areas or sections may be made without joints or seams.
– When repeated usage is possible, fiberglass is often the most economical form material.
3) Plastic Formwork: It comes as a individual structural elements like columns and walls. Various sized columns
and walls are available in the market. The formwork is very easy to install and uninstall and has a very high
repetitive nature. The ease of application makes it very useful where faster completion of work is a criteria.
4) Fiber-reinforced polymer (FRP) formwork system: FRP formwork is used where unique configuration required
for the arches and columns or any other structural parts. The FRP formwork pieces were produced using the hand
layup method using molds fabricated by means of a computer numerical control (CNC) machine. On site, the size
and weight of the formwork required the use of forklifts and scissor lifts for assembly.
5) Aluminium Panel System Formwork: System formwork has prefabricated modular components with casting
panels. The system formwork can suit the required shape of concrete structure. The speedy and quality
construction is the biggest advantage in this type while high initial cost is the main disadvantage and hence this is
not economical to use in low-rise buildings. But this is the most economical form of formwork type to be used in

8. high-rise building construction when it is having few (more that 10) typical storeys as it can be made in a single
storey complete formwork set form and a faster floor to floor construction can be achieved.
QUES-6) WHAT ARE THE JUMP SYSTEM AND SLIP SYSTEM?
ANS-6) JUMP FORM SYSTEM:
 Generally, jump form systems comprise the formwork and working platforms for cleaning/fixing of the
formwork, steel fixing and concreting. Jump form, often described as climbing form.
 It is suitable for construction of multi-floor vertical concrete elements in high-rise structures, such as
shear walls, core walls, lift shafts, stair shafts and bridge pylons.
 It is a highly productive system designed to increase speed and efficiency while minimizing labor and
time.
TYPES OF JUMP FORMWORK
 Normal jump/climbing form
 Guided-climbing jump form
 Self-climbing jump form
PROCESS EFFICIENCY :
 Fast construction can be achieved by careful planning of the construction process. Crane availability is
critical for normal jump form.
 Self-climbing formwork cuts down the requirement for crane time considerably. By allowing the crane to
be used for other construction work this may reduce the total number of cranes needed on site.
 The formwork is independently supported, so the shear walls and core walls can be completed ahead of
the rest of the main building structure. This can help to provide stability to the main structure during its
construction and can have the beneficial effect of taking the jump form core off the project critical path.
 High quality surface finishes are possible.
 The highly engineered nature of jump form systems allows quick and precise adjustment of the formwork
in all planes.
 A small but skilled workforce is required on site.
 It is easier to plan construction activities due to the repetitive nature of the work.
SLIP SYSTEM:
• Slip form construction, or continuously formed construction, is a construction method in which concrete is
poured into a continuously moving form. Basically, this method involves the continuous placing of concrete in a
shallow mould having the same plan as the building to be constructed.
• This rigid mould, or "slip-form" as it is called, forms the working deck which is jacked slowly upwards at a
controlled rate until the required elevation is reached.
 • Method of vertically extruding a reinforced concrete section and is suitable for construction of core
walls in high-rise structures – lift shafts, stair shafts, towers. Overview In the slip form method, paving is
done using a special-purpose slip form paver, without installing framing. With this method, concrete
structures with the same cross-section are finished continuously using a steel mold. This system is used
for ordinary concrete slabs and continuous reinforced concrete slabs.