What is a Concrete Grade Beam?
A concrete grade beam is a reinforced beam designed to act as a horizontal tie between footings or pile caps. It is typically constructed of concrete and reinforced with continuous reinforcement that is developed either within or beyond the supported column. The grade beam rests either directly on the soil or is suspended above it, spanning between piles. It is used to transfer the load of a building to the ground or to its bearing points, where its base distributes the load to the soil.
How is a Concrete Grade Beam Constructed?
The construction of a reinforced concrete grade beam involves a process of laying out the reinforcement, pouring the concrete, and ensuring the beam is properly supported and anchored. Once the reinforcement has been laid, the concrete is poured and allowed to cure. The beam is then inspected to ensure it meets the required specifications, such as adequate strength, proper anchoring, and correct support. Finally, the beam is tested to verify its strength and safety.
Concrete Grade Beam Construction Process
Following steps are involved
1. Preparation for Grade Beam Construction: Before constructing the grade beam, it is important to prepare the area by excavating and removing any existing material in the area. This is done to make sure that the grade beam is properly installed and that the finished grade beam is structurally sound.
2. Installing Grade Beam Formwork: Once the area is prepared, the grade beam formwork is installed. This formwork is used to create the shape of the grade beam and hold the concrete in place until it dries and sets. It is important to ensure that the formwork is securely fastened to the ground and that all the joints and corners are properly sealed.
3. Placing Reinforcement for Grade Beam: After the formwork is installed, the reinforcement for the grade beam is placed. This reinforcement is usually made of steel bars or mesh, and it helps to provide additional strength and stability to the grade beam. It is important to ensure that the reinforcement is properly placed and that it is adequately tied together.
4. Pouring Concrete for Grade Beam: Finally, the concrete is poured for the grade beam. This is done by using a concrete pump, which is used to fill the formwork with concrete. It is important to make sure that the concrete is properly mixed and that it is poured evenly. Once the concrete has dried and set, the grade beam is complete.
1. Preparation and excavation for grade beam
Preparation for Grade Beam with Piles: When the grade beam is used between piles, as shown in Fig. 1, preparation and excavation for the grade beam will begin after the pile construction is finalized. The trenches for the grade beam will need to be excavated at the same level.
Preparation for Grade Beam with Footings: When the grade beam is used with footings, excavation of trenches for the grade beam will be executed along with that of the footing.
Preparation for Grade Beam Above Ground: If the grade beam is constructed above the ground surface, then installation of forms will be the first step in the construction process of the grade beam. The ground surface will need to be leveled and prepared.
2. Formwork installation for grade beam
Steps for On-Ground Grade Beam Construction:
The first step for constructing a grade beam on the ground is to prepare the site and excavate necessary trenches. Once this is done, forms for the grade beam can be placed according to the dimensions provided in the design drawings. The bottom of the form should be placed before the sides. Instead of a bottom shutter, a flat soling brick will be installed along the grade beam. After this, either the reinforcement cage can be placed on the flat soling brick before the side shuttering is fixed, or one side of the form can be placed followed by the installation of reinforcements.
Steps for Above-Ground Grade Beam Construction:
For grade beams constructed above the ground, the formwork construction will be similar to that of a conventional beam. Shutters should be placed for the bottom and both sides of the grade beam. The formwork can be fully fixed, followed by the placement of reinforcements, or the bottom shutter can be fixed first, followed by the placement of reinforcements, and then the side shutters can be installed.
Inspection and Quality Assurance:
At the end of the grade beam formwork construction process, it’s important to ensure that the designated grade beam dimensions are provided and that there is sufficient reinforcement cover. Additionally, the strength of the shuttering, waterproofness, strength of the supports of the grade beam formworks, verticality of the side shutters and the location of the grade beam should all be checked.
3. Placement of Reinforcement for Grade Beam
The first step in the process of placing reinforcement for a grade beam is the construction of formwork or the laying of flat soling bricks at the bottom. Structural drawings provide details on the size and number of longitudinal reinforcements, number and spacing of stirrups, and any additional reinforcements required. After the formwork is in place, the number and size of top, bottom, and extra reinforcements, along with their lap length and placement, hooks, spacers, and the clear reinforcement cover should be checked to ensure proper placement.
4. Pouring concrete for grade beam
Step 1: Selecting Concrete
Ready mix concrete is usually preferred if the volume of concrete is large. However, if on-site machine mix concrete is employed, then the ratio of concrete constituents shall be found.
Step 2: Pouring and Compacting Concrete
The poured concrete shall be adequately compacted using vibration equipment or any other suitable means.
Step 3: Finishing the Top of Grade Beam
The top of the grade beam needs to be finished off.
Step 4: Stripping Shutters
The side shutters can be removed 24 hours after pouring concrete. However, the bottom shutter cannot be removed till the concrete achieves its strength. The time duration for stripping the bottom shutter depends on the clear span of the beam.
