FORMWORK
In continuation to attain the required strength of concrete, supports are required usually referred to as shuttering and technically referred to as Formwork.
Formwork is usually applicable in order to construct columns or during the filling of columns. It is applied around the corners of a column so that it can provide support until the column gets rigid.
Similarly, formwork is placed at first before going for the construction of homes or especially for building roofs. Structural iron is tied strongly around that formwork and then concrete has been inserted into it. As soon as the concrete gets rigid, the formwork can be removed.
There are three types of formwork usually used for the construction of commercial and residential projects in Pakistan:
Wooden Formwork:
Wooden Formwork is usually referred to as temporary shuttering. In this type of formwork, both vertical or horizontal supports are comprised of wooden planks, and the filling of concrete is directly applied above the supports. Wooden shuttering is considered to be a 3rd-grade formwork.
M.S Formwork:
The second type of Framework is M.S Formwork. In this type of formwork, vertical supports comprising of 2 inches M.S diameter of scaffolding pipes are used. In the case of horizontal or vertical spreading, plates of M.S are utilized. There are different sizes of M.S plates available in the market that includes 2/3 or 2/4 feet. M.S formwork is considered to be a second-grade formwork.
Cuplock Formwork:
The first grade of formwork that is usually used for industrial or commercial use is often referred to as Cuplock System. In the cup-lock system, the standards are used for vertical support, and then bracing is applied accordingly. The height of the standard is pre-decided according to the roof. The major benefit of this formwork is its simple installation. You just need to keep the vertical supports in a standing position and then the braces present in it automatically interlocks within the cup. There is a jack present on the upper side of a standard that you can toggle up or down by your own choice.
In cup-lock formwork, marine ply is used for horizontal spreading. The marine ply is 8*4 inches of a sheet and a waterproof sticker is placed on it. The major attribute of a cup-lock system is it’s characteristic of clear finishing of a roof due to its marine ply. There is no need for plastering of roofs made by marine ply.
Table Formwork:
The fourth type of formwork that is highly used in international industries referred to as Table Formwork. In table formwork, the topping is installed at the same time according to the design and on the basis of span or grid. It is an advanced type of formwork because the amount of wastage of material in this Formwork is very low. The installation of table formwork is also very easy and it can easily be dismantled.
Slip Formwork:
For vertical formwork, slip formwork is highly recommended. In this formwork, a low-quantity concrete filling has been done and the system automatically shifted upwards through eject. This type of formwork is used on a minor level in Pakistan.
Important steps to notice while doing Shuttering:
While going for the installation of the first floor’s roof, it is pertinent to notice that before going for the installation of vertical supports that are deployed for the ground floor’s roof, propping should be done beneath the ground floor. In this way, no crack or collapse would affect the slab of the ground floor after the exertion of the load of the first floor on the slab of the ground floor.
After the process of shuttering, the mechanism of leveling begins. The leveling could be done via the help of a strand or with the flow of water. The advanced mechanism of leveling is auto set leveling. Accuracy factor can easily be achieved with auto set leveling. It is mandatory to do cambering between the center of the room while shuttering. It means that the roof should be in an upward position up to 1 or ½ inch. After the removal of shuttering, the concrete will go back to its original state and then the roof will be leveled. In some cases, if the roof disrupts at the center then it will be a huge problem during the process of plastering. It should be ensured that there would be no gap during the process of roof concrete.
The main disadvantage of the shuttering of wooden planks is the increment of its GAP ratio. In this way, the slurry will cross through those gaps. The width of the wooden plank is 4’’ or 6’’ and gaps will increase after combining several joints and the chances of leakage of concrete slurry are increased. The concrete gets strength by slurry so the leakage should get some importance. Slurry should be properly packed, the contractors also use steel rail or cardboard on the wooden planks but it is better to avoid wooden shuttering.
In the shuttering of plates, the size of the plates is 2*2 and 2*4. In this way, the joint ratio is increased, and the chance of leakage of slurry occurred. The irregular joining of plates causes grooves to appear beneath the concrete. The proper masking tape should be applied to the upper joints of plates while doing shuttering.
In M.S formwork, proper oiling is required during shuttering. You can use shuttering oil, Diesel oil, or Mobil oil for this. In this way, the concrete will not stick to the M.S plates.
During the shuttering of marine ply, the oiling or masking tape plays an essential role for a neat & clean finishing.
According to the rates of 2020, temporary shuttering costs Rs 40-45pkr per sqft, M.S sheets cost Rs 60-65pkr, cup-lock costs Rs 80-85pkr per sqft in the market. You can purchase any one of them according to your budget.
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