Movement Joints In Concrete Walls

Early entry saws make a nice clean cut for decorative concrete joints.

Movement joints in concrete walls.

It allows for thermal expansion and contraction without inducing stress into the system. This can lead to stress concentrations resulting in subsequent spalling of the concrete. 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. A single row of short thick dowels provides reasonable shear transfer but suffer from deformation.

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. Concrete expansion joints are used to separate slabs and concrete from other parts of the structure. Movement joints are most commonly found between sections of building facades concrete slabs bridges pavements railway tracks pipelines and so on.

In road construction movement joints can be provided in the transverse direction to allow the expansion and contraction of a concrete slab due to temperature and subgrade moisture variation. Dowels are used to transfer shear across construction and movement joints in concrete. These are vertical joints or grooves formed or cut into the wall that allows the concrete to shrink without noticeable harm. In concrete walls the movement joints should normally be placed at a maximum spacing of 7 5m.

Why do we need them. They are usually either cast or drilled into the concrete. 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. Movement control aggregate concrete blocks position of movement joints consideration for the location of movement joints should be given at.

Expansion joints allow independent movement between adjoining structural members minimizing cracking when such movements are restrained. Staggers and movement joints in masonry walls other than clay brickwork should be engineer designed. Tial basement walls and the national ready mixed concrete association ref. 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.

Some designers recommend re ducing joint spacings by about 20 in walls with frequent openings such as doors and windows. 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. 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.