Movement Joints In Concrete Retaining Walls

As a rule of thumb it is normal to consider movement joints at approximately 6 m centres in straight lengths of autoclaved aerated concrete block walls.

Movement joints in concrete retaining walls.

Tial basement walls and the national ready mixed concrete association ref. In reinforced walls and 6m in unreinforced walls. The hight shear force is applied at the horizontal construction joints located at the lower level. Use of bedjoint reinforcement and moisture content of blocks when laid.

The friction of the concrete is the key factor that limits the movement. They are essentially vertical planes of weakness built into the wall to reduce restraint and permit longitudinal movement due to anticipated shrinkage and are located where stress concentrations may occur. 1 3 movement and restraint in concrete structures restrained movement is a major cause of cracking in con crete structures. 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.

8 to 12m external. Some designers recommend re ducing joint spacings by about 20 in walls with frequent openings such as doors and windows. Greater distances between movement joints 9 m and sometimes longer are possible in aggregate concrete blockwork walls depending on the location and block type. Typical movement joint spacing for unreinforced concrete masonry panels.

Precast concrete cantilever wall expansion joints shall be in accordance with the standard specifications section 6 11 3 3. In concrete walls the movement joints should normally be placed at a maximum spacing of 7 5m. 6 to 9m factors influencing spacing of joints are. These are vertical joints or grooves formed or cut into the wall that allows the concrete to shrink without noticeable harm.

Internal or external restraint can develop tensile stresses in a concrete member and the tensile strength or strain capacity can be exceeded. 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. 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. The weaker the mix the increased ability to accommodate movement.