Movement Joints In Concrete Walls

Concrete expansion joints are used to separate slabs and concrete from other parts of the structure.

Movement joints in concrete walls. Expansion joints should normally be provided at a spacing of not more than 30m between successive expansion joints or between the end of the structure and the next expansion joint. This can lead to stress concentrations resulting in subsequent spalling of the concrete. Saw cut contraction joints are ideal for decorative concrete because the joint is narrower and cleaner than a tooled joint. Why do we need them.

Movement joints such as control joints are one method used to relieve horizontal tensile stresses due to shrinkage of the concrete masonry units mortar and when used grout. It allows for thermal expansion and contraction without inducing stress into the system. In reinforced walls and 6m in unreinforced walls. Movement joint then a movement joint should be introduced into one of the two lengths or at the stagger as shown in diagram 4.

In concrete walls the movement joints should normally be placed at a maximum spacing of 7 5m. These are vertical joints or grooves formed or cut into the wall that allows the concrete to shrink without noticeable harm. For tips on this check out bob harris s video or get a copy of his guide to stamped concrete joints are covered in chapter 23. Movement joints should not coincide with door or window openings due to the di culty in continuing.

Expansion joints allow independent movement between adjoining structural members minimizing cracking when such movements are restrained. Change in wall height or thickness see figure 1 figure 2 change of loading see figure 3 abutments of walls and columns see figure 4 junctions of dissimiliar materials see figure 5. Some designers recommend re ducing joint spacings by about 20 in walls with frequent openings such as doors and windows. Staggers and movement joints in masonry walls other than clay brickwork should be engineer designed.

Dowels are used to transfer shear across construction and movement joints in concrete. They are usually either cast or drilled into the concrete. Tial basement walls and the national ready mixed concrete association ref. Early entry saws make a nice clean cut for decorative concrete joints.

Movement control aggregate concrete blocks position of movement joints consideration for the location of movement joints should be given at. 4 recommends a contraction joint spacing of 30 times the wall thickness or 20 feet for an 8 inch thick wall 30 8 240 inches 20 feet. Contraction joints are usually about 0 25 inches wide and about 1 2 to 3 4 inch deep and are provided at intervals of not exceeding 30 feet.