A key joint is a pre-manufactured device used to create control joints in concrete structures. As freshly-poured concrete begins to dry, it tends to shrink or contract. This contraction can lead to cracks or breaks in the surface of the concrete, or in tiles and other floor finishes installed over the slab.
What is key joint?
Product description: Key Joints are part of a metal joint system which qualifies loads to be transferred between adjacent slabs while allowing horizontal movement and limiting differential deflection.
What is a keyed construction joint?
#2 Keyway Construction Joint
The keyway construction joint is probably the most complex construction joint. This joint requires the time to build or buy a wooden, plastic, or metallic keyway and install the material into your formwork. The keyway will act as the slab edge for the pour.
What are the three types of concrete joints?
Joints create a plain of weakness in the concrete directing the concrete where to crack. There are three types of joints: Contraction Joints, Construction Joints and Isolation joints.
What are the types of joints in concrete?
In slabs, there are three types of joints: Isolation joints (also sometimes functioning as expansion joints) Construction joints (which can also function as contraction joints) Contraction joints (also sometimes called control joints)
What is the disadvantage of keyed joint?
Too much securely fixed keyed joint might become difficult to dismantle. Causes shaft imbalance. They introduce stress points due to the notch effect and reduce shaft strength. Possible axial displacement of hub unless locked by an extra component such as circlip or set screw.
What is the purpose of a keyway?
A keyway is a long slot cut into a component to accept a key that engages with a similar slot on a mating component so that the two components do not move against each other. If the key is not fitting properly in both the flywheel and crank shaft keyways, replace the key.
What does keyway in construction mean?
a groove in a shaft, the hub of a wheel, etc., for receiving part of a key holding it to another part. a slot in a lock for receiving and guiding the key. (in poured-concrete construction) a longitudinal groove in a footing, or in a pour that has set, providing a key for newly poured concrete.
What is a bulkhead concrete?
A bulkhead is used in a concrete footer where there are steps up or down. These bulkheads allow a change in concrete height, and serve as a stop gate for wet concrete. They are generally made from lumber and plywood and can be readily removed after the concrete has dried.
What is a bulkhead in concrete construction?
A bulkhead is a retaining wall, such as a bulkhead within a ship or a watershed retaining wall.Construction materials commonly used include wood pilings, commercially developed vinyl products, large boulders stacked to form a wall, or a seawall built of concrete or another hard substance.
How big can a concrete slab be without expansion joints?
Rule #1 Keep joints as square as possible. Rule #2 In order to prevent intermediate cracking, space joints (in feet) no more than 2 3 times the slab thickness (in inches).
What is the best concrete expansion joint material?
Why Silicone is the Best Expansion Joint Filler
Silicone provides an excellent alternative to the three expansion joint fillers above, and for a few reasons.
Do I need control joints in concrete slab?
Concrete expands and contracts with changes in temperature and moisture. If not properly controlled, cracks can begin to appear. Placement of concrete control joints and expansion joints are crucial when designing and pouring concrete slabs and sidewalks.
What are the types of joints?
A joint is the part of the body where two or more bones meet to allow movement. Generally speaking, the greater the range of movement, the higher the risk of injury because the strength of the joint is reduced. The six types of freely movable joint include ball and socket, saddle, hinge, condyloid, pivot and gliding.
Do you need expansion joints in reinforced concrete?
All concrete will shrink slightly as it dries and, when it’s set, will expand or contract depending on the ambient temperature. To prevent cracks from forming, concrete expansion joints should be incorporated to allow for movement, particularly in slabs with a surface area exceeding 6m2.
Why are joints needed?
Joints are where two bones meet. They make the skeleton flexible without them, movement would be impossible. Joints allow our bodies to move in many ways.
How much torque can a keyway handle?
The limiting pressure point of a keyed shaft is the keyway side of the male shaft, provided the proper key material is selected. Thus, 270 Nm is the maximum torque that can be transmitted before the 19 mm diameter keyed shaft plastically deforms.
What is key steel used for?
Key Steel is widely used for many general engineering applications. Typical key steel applications include taper, gibhead, plain and parallel keys.
What is Kennedy key?
The Kennedy key consists of two square keys. The hub is bored off the centre and the two keys force the hub and the shaft to a concentric position. Kennedy key is used for heavy duty applications.
How are keyways measured?
Metric keyways are dimensioned by width and depth as measured from the radius of the shaft to the center of the keyway. See dimensions W and h in Figure 1. Unless otherwise specified, the shaft keyway is assumed to be standard.
What types of keys are there?
Types of Keys
- Skeleton Key. Also known as a passkey, a skeleton key is a simple key with a cylindrical shaft and a single toothed end, which is used to open warded locks.
- Abloy Key. The Abloy key is used on disc tumbler locks.
- Dimple Key.
- Paracentric Key.
- Tubular Key.
- Keycard.
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