Why Are The Joints In A Concrete Block Wall Tooled

Joints that were tooled early often have multiple ridges on the surface of the mortar parallel to the direction of the tool.

Why are the joints in a concrete block wall tooled.

When shrinkage is restrained by contact with supporting soils granular fill adjoining structures or reinforcement within the concrete tensile stresses develop within the concrete section. The open texture promotes a good mechanical bond between the plaster and the masonry. This space is filled with a compound made of cement aggregate and water referred to as mortar. Joints in concrete slabs can be created by forming tooling sawing and placement of joint formers.

Contraction joints are intended to create weakened planes in the concrete and regulate the location where cracks resulting from dimensional changes will occur. Control joints are typically required in exposed above grade concrete masonry walls where net aesthetic shrinkage cracking may detract from the appearance of the wall and to limit moisture or air infiltration. A mortar joint is the space between concrete blocks or bricks in masonry construction. The pre planned cracks will provide a better finish concrete product and will be formed in specific locations where those cracks could be monitored.

A concrete control joint that was formed during the pour or placement of the concrete usually is tooled to round the upper edges of either side of the joint and the joint extends some depth into the concrete or in some cases such as sidewalks and some floors the control joint may extend through the full depth or thickness of the concrete. Open textured concrete masonry units laid with flush non tooled joints should be specified on walls intended to be plastered. Joints should be tooled when they are just stiff enough to support a thumbprint for best compaction. If it isn t tooled correctly water can accumulate in the joint.

One of the main purposes of mortar is to act as a bonding agent between the blocks holding the wall together. Concrete joints are normally used to prevent cracks when the concrete shrinks by creating forming tooling sawing and placing joint formers. These are known as head joints and must be completely filled and tooled for maximum weather resistance. New concrete masonry walls should be properly aligned and free from any surface contamination such as mortar droppings or sand.

The v joint does not protect from water as well as the concave joint because of its geometry. On tuckpointing projects old mortar is removed and joints are cleaned out so they can receive new mortar which has to be tightly packed into the space. Shrinkage cracks in concrete masonry are not a structural concern. Joints are not properly compacted if tooled when they are too stiff.

The concave joint is the most common joint that is used as it is also known as the best joint for preventing water penetration. Contraction control joints are placed in concrete slabs to control random cracking. Joints are simply pre planned cracks. Some forms of joints are.

Ridges form as the wet mortar sticks to the tool. These joints must be aggressively worked and often have a darker appearance in the completed wall. Click here for diagram.