What is a void slab former?
A voided slab is a system that removes the non-working or excess concrete from the structural slab and replace it with void formers. What are the types of formers used to make void slabs?
What is a slabvoid form?
General Description SlabVoid® is a corrugated paper carton void form that helps eliminate severe damage to a structural concrete slab by creating a space between the slab and underlying expansive soils. The SlabVoid® material provides a temporary platform for the placement of liquid concrete.
What are the advantages of voided slabs?
The advantages of voided slabs are: Weight reduction of slabs is achieved by the voided slab system. This would help to achieve longer spans, lighter foundation, and smaller columns. The voided slab system provides design freedom in building construction. It helps to provide an open floor plate with lesser numbers of columns and beams.
What is a voided-slab floor?
As a result, some long-span structural steel floors can be converted to voided-slab floors. The reduced weight of the floor slab using voided slabs allows a reduction in concrete and steel in floors, columns, and footings, saving money and reducing the total building weight, allowing lighter foundations.
What is a void in concrete?
In hardened HCC, a void is an empty space, other than a crack, in the cement paste that contains nothing but air.
How do you fix a void on a concrete slab?
A sand-cement grout can be used to fill voids under concrete slabs. This mix of sand, cement, and water is pumped through holes drilled to fill up the voids. While this method of slab jackingslab jackingIn civil engineering, concrete leveling is a procedure that attempts to correct an uneven concrete surface by altering the foundation that the surface sits upon.https://en.wikipedia.org › wiki › Concrete_levelingConcrete leveling - Wikipedia is cost-effective, there are major drawbacks to opting for this type of repair.
What does slab on fill means?
Slab on Fill is also known as Concrete slab. It is one type of grade on slab. Slab on grade is also known as Floating slab foundation. Slab on fill layer is made up of a mixture of broken stones, masonry, and concrete. Slab on Grade is made up of the layer of Bitumen and gravel.
What is a void box in concrete?
Box Void forms are designed to hold up the weight of fresh concrete long enough for the concrete to cure and support itself on piers or beams. Since it is a paper product, it absorbs the moisture of the surrounding soil and concrete and it's supportive strength gradually diminishes.
How do you tell if there is a void under a concrete slab?
A professional mudjacker uses Ground Penetrating Radar, or GPR, to locate and map out voids underneath concrete using high frequency radio pulses. These pulses indicate the presence of not only voids, but metal, wood, and PVC pipe as well, as each material produces a unique signature.
What causes voids under concrete slabs?
Voids under concrete slabs are caused by various things including, Erosion – Excess water around a concrete slab leads to soil erosion and then voids. Two common causes of erosion are drainage issues and leaky plumbing. Soil settlement – Soil settlement is another cause of voids under a slab.
Is slab on grade good?
There are good reasons for building or buying a house on a slab, such as cost savings and less risk of damage in certain instances. The disadvantages include that heating and cooling units may have to be installed on the ground floor, which takes up living space. There is also a potential for cracks.
Can slab on grade have a basement?
Slab-on-Grade Construction is best if: A slab-on-grade means no basement, no basement walls, just one slab of concrete on which you build your house. They aren't suitable for all building sites, which we will get into later, but for now let's assume you can build on one.
Is slab on grade cheaper than basement?
Slab foundations on average are about $10,000 cheaper than most crawl spaces. Slabs are much cheaper if a crawl space or basement must be carved out of solid rock, which can be very expensive. Slab foundations make it less likely that radon gas will leak into the house.
What is the purpose of void form?
Void Forms are sacrificial formwork elements designed to provide Void Space between Expansive Soil and the Foundation, while providing a temporary support formwork for the weight of concrete until it has reached a specified strength.
Why are void forms used?
Void forms are sacrificial formwork members designed to provide a space between the concrete foundation and expansive soil, i.e., to protect the foundation from the heave of the underlying soil.
What is a void in construction?
In construction, a floor void is typically a vertical opening or hole that is left in the floor construction either to accommodate services, or allow the installation of a staircase or, as an aesthetic feature.
How do you fill a void in a garage slab?
3:2417:49How to Fill Voids Under Concrete Slabs with Secure Set Spray FoamYouTubeStart of suggested clipEnd of suggested clipTen feet long 6 inches thick and it's elevated from 0 to about 7 inches of void on one side and soMoreTen feet long 6 inches thick and it's elevated from 0 to about 7 inches of void on one side and so this is designed to move underneath your slab or whatever you were trying to remedy.
How do you fill a concrete slab?
1:255:31How to fill a crack or joint in an indoors concrete floor - YouTubeYouTubeStart of suggested clipEnd of suggested clipA pancake mix type density. That allows it to flow into the cracks. And the joints in that area byMoreA pancake mix type density. That allows it to flow into the cracks. And the joints in that area by the way you can also use this material to fill in cracks.
How do you fill a void on front steps?
Crushed limestone known as “3/4 down” or “1/4 down” may provide a better fill than sand. This material contains granules of different sizes and will compact quite well when damp. It is easy to pack into small areas, like that under your steps, and will resist some moisture intrusion.
How do you fill concrete?
1:385:16How To Repair Concrete | Pro Tips For Repairing Concrete - YouTubeYouTubeStart of suggested clipEnd of suggested clipOr you can use a vinyl concrete patching agent and a putty knife to fill it in for a wider crack youMoreOr you can use a vinyl concrete patching agent and a putty knife to fill it in for a wider crack you will need to use a small sledgehammer.
What is a slab void?
SlabVoid® is a corrugated paper carton void form that helps eliminate severe damage to a structural concrete slab by creating a space between the slab and underlying expansive soils.
What is a Sureround PierVoid?
SureRound PierVoid ® – Pre-manufactured carton void form, having a curved, radial, vertically-supported edge adjacent to the drilled pier that conforms to the pier diameter
Can concrete be used to displace concrete volume?
Can be used to displace concrete volume where reduction in weight or cost is a consideration
Why are void forms used in concrete?
They are also used underneath a concrete slab to prevent severe damages caused by expansive soil.
What are void forms made of?
These void forms can be constructed from corrugated paper, expanded metal, metal sheet, molded plastic, molded paper, Styrofoam, and wood.
What is a degradable void form?
Degradable Void Forms. Degradable void form is manufactured from easily degradable materials like molded paper and corrugated paper. It is suitable for a construction site where there is a sufficient water supply in the environment to degrade the void form material before soil expansion occurs.
How deep is a void form?
Moreover, void forms are utilized to decrease soil excavation and reduce the quantity of concrete. The depth of void forms under foundations ranges from 5 cm to around 60 cm based on the underlying soil's potential for upward movement. Furthermore, several types of void forms are available to use, like degradable void form, ...
Where should void forms be stored?
Void forms should be stored in a dry place. Void forms are also required to be protected from moisture until the concrete is poured. Plastic sheeting should be installed above degradable void forms. The degradable void forms are lightweight, easy to install, cut easily, and available in standard strength and sizes. 2.
Can void forms be used under slabs?
A non-collapsible void form system should be used under grade beam only. This type of form should not be utilized under a slab area with a long span between stiffening beams and thin unreinforced slab elements.
Can void form be used under reinforced concrete?
The collapsible void form should not be used under the reinforced concrete slab. 4.
What is a slab on a slab foundation?
A slab-on-grade foundation—also known as a floating slab foundation—is a structural engineering practice in which the concrete slab that will serve as the foundation for a building or other structure is formed from a mold that is set into the ground. The concrete is then poured directly into the mold, leaving no space between the ground and the structure. This method of foundation construction is most commonly used in warmer climates where (1) seasonal freezing and thawing of the ground is less of a concern and (2) where there is no need for heat ducting to be installed beneath the floor of the building.
Why is slab on grade foundation so popular?
Moreover, slab-on-grade foundations are considered less vulnerable to infestation from termites and other pests because there is no hollow space between the ground and the bottom of the structure.
Can slab foundations be jacked up?
It can also sometimes be difficult to extend or remodel this type of foundation, and, because slab- on-grade foundations cannot be easily jacked up, they are more prone to damage caused by sinking or uneven settling than other types of foundation that include deep footings such as piles or piers.
What is a voided slab?
The reduced weight of the floor slab using voided slabs allows a reduction in concrete and steel in floors, columns, and footings, saving money and reducing the total building weight, allowing lighter foundations. Some voided-slab systems can reduce construction time, especially precast systems or those placed on flat-plate forming systems.
Why are void slabs beneficial?
Voided slabs are beneficial in seismic design, since the reduced dead weight of floors results in lower seismic forces applied to structures.
How much weight can a voided slab reduce?
By using these voided systems, Mota says it’s possible to lighten the weight of slabs as much as 35%. “A 21-inch-thick slab can be reduced by the equivalent of 4 to 5 inches in thickness of concrete or 30 to 40 pounds per square foot of dead load,” he says. He adds that a typical slab with 40-foot spans is 16 inches thick based on ACI 318 Table 9.5a, but a voided slab with these spans can reduce the equivalent solid thickness to about 12 inches. This reduced weight of building floors also permits engineers to reduce columns, walls, and foundations as much as 40%, although concrete can’t be removed from all locations in a floor slab; voids are omitted near columns to maintain slab punching-shear capacity.
How to build a bubbledeck?
Dan Windorski, project manager for GRAEF, explains that the process starts by assembling bubble cages of steel and plastic and then precasting the bubble cages in panels that are typically 8x30 feet. The panels, or filigree, include most of the required reinforcing. These panels are trucked to the jobsite and positioned by crane, saving time by eliminating the deck forming operation. Afterward, workers place concrete on top of the precast filigree to complete the floor, with the fresh concrete covering the rest of the plastic voids and wire trusses that protrude from the precast section to ensure bond between the precast and cast-in-place concrete.
How are plastic voids installed?
First, deck forms are set up and the bottom layers of reinforcing steel are installed. To facilitate the installation of the plastic voids, the system’s bubbles come bundled to a jobsite in 1/4-inch-diameter steel wire cages 8 feet long with six or seven voids per bundle ( depending on void sizes). Workers can easily cut the cages down in size to fit the required spaces then use tie wire to secure them to the first layer of reinforcement (which typically is installed in both directions) before proceeding to place the top layers of rebar. Concrete is placed in two lifts: the first covers the bottom layer of reinforcement and a portion of the plastic voids. This concrete holds the voids in place so they can’t move or float upward when the second lift is placed. When the first concrete lift is stiff but still fresh, the second lift is placed to the finished elevation.
How long does a voided slab span?
Voided slabs can save money on a project but there are other important reasons to consider using them. The key advantages of voided slabs start with spans 25 feet and longer:
What is the third method of forming voids?
A third method of forming voids is used for projects that only require one-way voided systems. To form the voids, contractors position cylindrical concrete forming tubes made from paper fiber, the same material used to form columns and footings.
What is a slab on grade?
Slab on Grade: Slabs which are directly laid on the earth, to support walls and other structural elements are called as Slab on grade or Grade Slabs. This type of slab is casted directly on ground level. Grade slab itself acts as a foundation for the building which does not require further footings. Grade slabs are framed in areas ...
What is grade slab?
Grade slabs are framed in areas where the ground doesn’t freeze. This type of slabs may or may not have reinforcement in it. The decision of inserting reinforcement is based upon the floor loads and local building codes. The thickness of Grade Slab is kept minimum 4 inches. If there are concerns regarding soil characteristics like porosity, the thickness of the slab is further increased. And for safety, a layer of gravel & bitumen are laid on earth before laying concrete slab to prevent the entry of moisture content into the slab.
What is a supported grade slab?
Supported grade slab or slab on grade foundation is chosen when the traditional footings are already framed on site to raise the columns. From the below fig, it is clear that the wall stands on a footing and The grade slab is resting on a layer of gravel and moisture barrier. The formwork used for plinth beams are acted as batter boards for slab mould. An expansion joint is provided between concrete slab and wall to relieve the stress during high-temperature days. Control joints are laid out in a planned grid using chalk lines, these joints help to control random cracking on the slab.
What is monolithic grade slab?
Monolithic Grade slab doesn’t have any footings, the concrete slab itself acts as a footing for the building; and columns, walls are raised from the grade slab. This type of slab is framed by providing batter boards around the slab as per plan and pouring the concrete inside batter boards. These batter boards act as a mould to identify ...
Why is the perimeter of a grade slab thicker than the rest of the surface?
The perimeter of the Grade slab is thicker than the rest of surface, this thicker section acts as a mini footing and helps to distribute top loads more evenly across the surrounding soil.
What is the purpose of a batter before a concrete slab?
Before casting slab on grade, the earth is excavated up to the required depth and compacted to expel air voids. Batters are marked and placed in position as per plan before concrete pour. These boards act as a concrete mould, which helps in identifying slab corners.
How many different types of slabs are there?
In this article, you are going to learn about Slab on grade. As we already discussed about 16 different types of slabs which we usually used in construction. If you want to know? You can refer Here.
Why is there a void under my slab?
Erosion from Plumbing Leaks or Poor Water Drainage. If your foundation wasn’t built to drain water away from your slab foundations, there is an increased chance of topsoil erosion that can cause a void under your foundation. Poor drainage channels and improper foundation sloping can result in a loss of structurally important foundation soil.
How to fill a void under a concrete slab?
The void is then filled with sand and sealed with a concrete mixture that is level with your slab. Sand filling must be properly compacted so that your under-slab void doesn’t reform.
What is sand cement slurry?
This mixture of sand, cement, and water is pumped through holes drilled in a slab foundation to fill voids underneath. While this type of slab jacking can be cost-effective, there are some potential drawbacks to going for this type of repair.
Why does my slab foundation have voids?
There are two main culprits to voids under a slab foundation, and they both revolve around moisture. In some instances, these causes are unavoidable. However, there are some cases in which you can help prevent these problems from leading to foundation damage.
What causes voids in concrete slabs?
Faulty under-slab plumbing can also contribute to the formation of voids. Water build-up from leaky pipes underneath building structures will trigger further soil erosion .
Is polyurethane foam good for void filling?
This can be especially beneficial if voids are holding water. Minimal downtime with repaired slabs almost immediately usable after repair.
Does a Void Under Your Slab Foundation Need to be Repaired?
Voids underneath concrete slab foundations can lead to settlement. Settlement can cause several symptoms including:
