Category: Walls

For floor and roof slabs, it is desirable to use concrete of low shrinkage characteristics.

It is recommended to provide short spans for the floor slabs.

Smooth slip planes are provided between the roof slabs and brick walls. Because of this arrangement, cracks will be developed only at the re-entrant corners. These cracks can be easily covered after the complete construction is over. Figure 17.20 Expansion joint at foundation level Figure 17.21 Sliding joint

Sliding joint is provided when one part of a structure has a tendency to slide over the other due to variations in temperature and moisture content. Figure 17.21 shows the details of a sliding joint at floor level.

Isolation joint is similar to expansion joint but provided under the following conditions: Figure 17.18 Expansion at corner of walls Figure 17.19 Expansion joint at roof level

Providing horizontal and vertical expansion joints in walls helps to reduce the cracks to a considerable extent. Horizontal and vertical expansion joints absorb vertical and horizontal movement respectively. In general, expansion joints have to be provided for every 15 m. The sealant used for joints are natural or cellular rubber, bitumen, expanded plastics, coconut pith,…

Depending on the type of foundation soil, the foundation has to be designed and the supporting masonry walls should be designed with adequate stiffness. Such a design will help to control excessive shear of flexural stresses in the masonry.

Following are the preventive measures which could minimise the cracks in brick masonry.

Causes Cracks are frequently found in brick masonry walls due to some of the reasons given below.

In an eccentrically loaded wall, there is an axial load and a bending moment. These two may be combined into a single resultant load acting at a distance. This is known as equivalent eccentricity (Fig. 17.15). Figure 17.15 Equivalent eccentricity The stress distribution due to axial load and the bending moment are combined to get the…