Formwork removal: know the right time and precautions (2023)

FAQs

What precautions are to be taken while removing the formwork? ›

The concrete should be removed first. Shuttering forming soffit to slabs should be removed next. Shuttering forming soffit of beams, girders or other heavily loaded shuttering should be removed in the end.

After pouring and finishing the slab, you should wait 24-48 hours before removing concrete forms. You can remove the formwork once the concrete has enough strength to keep it from cracking. Concrete naturally contracts as it cures, so it should pull away from the forms and make them easier to remove.

What Happens If The Formwork Removed Early? if you remove formwork immediately, the columns and beams sides may bulge if the concrete has not hardened. And sides may go out of plumb or line. If you do not get enough strength, the system may be distracted or collapse.

The time required before formwork removal depends on the structural function of the member and the rate of strength gain of the concrete. The grade of concrete, type of cement, water/cement ratio, temperature during curing etc. influence the rate of strength gain of concrete.

Sharp edges on formwork, protruding nails, snap ties, conduit, and bolts can cause pinches, cuts, scrapes, abrasions, and other injuries. Protruding rebar can cause cuts, abrasions, and impalement.

The major sequences of construction are marking, excavation, concreting, brick masonry, roof laying, flooring and finishing.

There are three stages in formwork operations: 1. Assembly and erection 2. Concrete placement 3. Stripping and dismantling.

Walls and columns can be removed after about 24-48 hours

Slabs, with their props left under them, can typically be removed after 3-4 days. Soffits, with their props left under them, can be removed after one week. Props supporting slabs under 15 feet can be removed after one week.

Remove the forms too soon, and the structure or finished product can be ruined. Remove them too late, and the concrete will get too hard to properly finish. Most concrete forms can be removed after 24-48 hours of curing. However, for some large structural builds, forms can stay on for over a week.

What are the precautions to be taken while placing the concrete in formwork? ›

The general rule of thumb is that concrete takes about 28 days to dry for every inch of slab thickness. Within 24 to 48 hours, the concrete will be ready for foot traffic.

Removing formwork

When the concrete has enough strength to support the weight it must bear (seven days) strip the forms away. Do not use a metal tool against the surface to pry off forms because you may cause damage.

Concrete formwork striking times

Walls, columns and other vertical formwork can usually be removed after 24 to 48 hours. If you're using fast-drying cement, this could be as soon as 12 hours. For concrete slabs, formwork can usually be removed after 3 days and props after 2 weeks.

A formwork safe work method statement (SWMS) is one of the backbone pieces of formwork documentation. Your work method statement - which you can see an example of to the right - enables you to properly document how your projects, teams and workers approach formwork operations in a safe manner.

It consumes time in decision making based on the site constraints, availability and cost of the project. These are different factors which affects the formwork system selection.

Three general principles govern formwork design and construction: Quality accuracy of the concrete shape and the final finished surface quality. Safety strength of the formwork structure. Personal safety of people, both carpenters and the public.

What is a good formwork should satisfy the following requirements? ›

1. It should be strong enough to withstand all types of dead and live loads. 2. It should be rigidly constructed and efficiently propped and braced both horizontally and vertically, so as to retain its shape.

The main types of formwork systems in use now are: System column formwork. Horizontal panel.

First check formwork before you allow placing of reinforcement. This is necessary as certain formwork defects can't be corrected or are difficult to correct after reinforcement is placed in position.

2.2.2 Steel Formwork

Steel sheet plates conforming to IS 2062 or IS 8500 or IS 1977 may be used for form lining and rolled sections and tubes conforming to IS 2062 or IS 8500 or IS 1161 may be used for steel forming and bracings.

Improper curing reduces the strength gain in concrete both at the early stages and in long term. The formation of early cracking in the concrete surface leads to the ingress of moisture and other harmful compounds and low strength gain.

For the majority of concrete structures, the minimum curing period at temperatures higher than 5°C is seven days or until the concrete strength reaches 70% of specified compressive or flexural strength, as per ACI 308.1R. It is possible to decline the curing period to three days if high-early strength concrete is used.

Slabs & Wall Curing

For walls proper water curing should be done, at least three times a day. For pillars it should be covered with Gunny or strand and it should be always in wet condition.

How long does concrete continue to get hard? ›

By seven days, your concrete should be cured to at least 70 percent of its full strength. You will probably be able to drive on it without damaging it, although you may want to hold off on rolling heavy equipment over it. In 28 days, you can treat your concrete as fully hardened.

Once the concrete is poured the curing process begins immediately. To protect your new slab and ensure an exceptional finished product you should wait 24 hours for foot traffic (including pets), 10 days to drive light vehicles or add furniture, and 28 days for heavy pick-up trucks and RVs.

How Much Weight Can a Concrete Driveway Hold? Typically, concrete driveways that are 4″ thick can withstand loads of regular vehicles, which is approximately 8,000 pounds. A 6″ thick concrete driveway can withstand heavy-duty trucks that can around weigh about 70,000 pounds.

After pouring and finishing the slab, you should wait 24-48 hours before removing concrete forms. You can remove the formwork once the concrete has enough strength to keep it from cracking. Concrete naturally contracts as it cures, so it should pull away from the forms and make them easier to remove.

De shuttering period relates to the maturity of concrete and depends on the ambient temperature. Forms shall not struck until the concrete has reached strength at least twice the stress of which the concrete may be subjected at the time of removal of form work.

Freshly placed concrete should be protected from rain for at least 12 hours from its placement. After that, the rainfall rarely influences concrete properties.

Many construction specialists recommend watering it down five to ten times per day, for the first week, starting 2-4 hours after it has been poured. The first two to four hours lets the concrete “finish”, which refers to the setting process.

If you do not do watering of the concrete, the poured concrete will not develop the strength what was expected to achieve within 28 days. The loss of strength will invite repairs related to the restoration of strength.

Can I use 2x4 for concrete forms? ›

You can use 2- x 4-inch boards for concrete forms as long as the slab is not too thick. If the finished concrete slab will have visible edges, make sure the fasteners do not pass through the boards and into the concrete. Framework for a 12-inch concrete slab should have stakes no more than 24 inches apart.

Follow the engineer's design drawings when erecting or dismantling formwork and shoring and reshoring. Wear personal protective equipment to protect you from falling objects, falls, and prevent contact with machinery, components or tools.

Forms can be pulled away from the sides of the concrete slab with the use of minimum strength, but if a form becomes challenging to remove then a pry bar helps to loosen the form in the concrete when pried upwards from the ground.

For proper curing concrete needs moisture. Continuity in curing is a must; alterations of wetting and drying promote the development of cracking. If during curing the concrete is allowed to dry out - as may happen in hot weather - the chemical stops right at the point where the concrete loses its moisture.

Concrete typically takes 24 to 48 hours to dry enough for you to walk or drive on it. However, concrete drying is a continuous and fluid event, and usually reaches its full effective strength after about 28 days.

Removal of formwork.

Reshoring shall not be removed until the concrete being supported has attained adequate strength to support its weight and all loads in place upon it.