Types of foundation reinforcement. Requirements to reinforcement details. Technical features of mounting reinforcement for different foundation structures.
Concrete turns into reinforced concrete due to the foundation reinforcement. Specific design of reinforced concrete foundations enables them to take load directed, beside the compression, at bending and stretching.
How to reinforce the foundation correctly
Firstly, the reinforcement bars must be clean and free of dirt and debris. Only pure reinforcement adheres well to concrete. The frame has two types of detailing (for certain purposes): operational and distributive. The purpose of operational reinforcement consists in assuming external loads and own weight of the building. Distributive reinforcement spreads the load on the entire framework.
The connection between the fittings is provided by welds or wire bundles. For reliability reasons, welding is used more often. But if the expected load on the foundation is small, you can manage by binding wire. In general, the reinforcement cage is fastened on the corners of the foundation. If the diameter of the reinforcing rods is at least 25 mm, they are bonded by spot welding or wire. If their diameter exceeds 25 mm, the arc welding is applied.
Remember: throughout the frame at least half the reinforcing intersections must be sealed; at the corners it is recommended to connect all joints.
If your reinforcement has a diameter of maximum 40 mm, the connection is made with an overlay, while the welded joint shouldn’t be too short, otherwise the mount may be destroyed. For any type of foundation it is better to use ribbed bars, as they are firmly connected to the concrete.
If the future one-story home is lightweight and narrow, one can use reinforcement bars of 10 mm in diameter. If the house is two-storey or wide (long), it is necessary to use 12 mm reinforcement bars.
Reinforcement of monolithic strip foundations
Depending on the width and height of the strip foundation reinforcement can be made in two or more layers of mesh in 6-10 in increments. When dealing with typical strip monolithic foundation width of 16 in and height of 20 in, horizontal and vertical mesh padding can be 4-6 in on all sides. In the case of a high foundation vertical spacing between horizontal reinforcement bars may be 12 to 16 in.
The horizontal spacing between the vertical reinforcement may be equal to 12 in or more, and the distance to the edge of the concrete is ? – 4 in on each side. As a result, the amount of reinforcing meshes and the step between them is calculated basing on the foundation load.
Reinforcement of pier foundation
Reinforcement of pier foundation is quite simple. Here sufficient foundation reinforcement details are 4-6 long ribbed reinforcement bars and a few thin smooth rods to exactly band them. Long rod must have a diameter of 10-12 mm, for the smooth one 6 mm is enough. If a pier is too narrow (e.g. 5 inches), it can be reinforced with two rods. When the pier is 5-7 ft long, reinforcing bars can be bound at a distance of 16-20 inches. If the foundation is constructed for the weighty building, the joints should be welded. Pier foundation reinforcement is done so that after pouring the concrete the bars protruded for 4-8 inches. Thus, it is convenient to bond raft foundation reinforcement details to it.
Pile foundation is reinforced similar to the pier foundation. The only difference is that the vertical reinforcement is arranged in a circle, not a square. You can use 3-5 bars of 10 mm in diameter.
Technology of foundation reinforcement
First, get prepared the reinforcement bars of required length, including thin rods for binding. The bars are bent to be installed in the corners.
In a trench dug for the foundation, reinforcement bars of the bottom row are laid on a sandy base. To provide the required distance between the future foundation and the bars, the latter are just laid on the bricks embedded in the sand. The bars are linked together into a single thread along the length, as well as crosswise in a horizontal plane. Herewith, the distance between the bearing bars along the width is strictly observed and frame parts are aligned along the axes of the foundation.
Next, upper bearing bars are mounted. For this purpose they are hung and fixed in position, for example, on the trench sticks laid across, and then bound with transverse bars in the frame.
Horizontal transverse bars are bound to the upper reinforcement bars as well. The result is a reinforcement cage standing on bricks.
When installing reinforced concrete foundation, it is important to control the layout of reinforcement rods regarding to the central axis of the foundation strip. To do this, the filaments corresponding to the foundation axes are stretched on the stakes over the trench. The reinforced foundation frame is oriented according to them using a plumb. It is also important to make the frame strictly vertical.