CONSTRUCTION MORTAR: ITS IMPORTANCE, PREPARATION, MIX PROPORTION, AND USES
Mortar is a combination of sand, a binding agent like cement or lime and water, used in masonry buildings to bridge the space between building blocks. It is applied in the form of a paste which then hardens and binds the masonry units such as stones, bricks, or concrete used in the construction. This article deals with the importance of construction mortar, its preparation, mortar mixes used for the various work and important points to be remembered regarding the mortar mix.
What is the Importance of Mortar in Construction?
The uses of masonry mortar used in construction are:
Construction mortar is used as a bed to even out the irregularities of the individual masonry units. The more even the individual stone or bricks surface, the thinner will be the mortar bed.
The mortar should provide some adhesiveness between the individual stones or bricks.
The mortar used in construction must transfer the compressive, tensile, and shear stresses between adjacent units and it must be sufficiently durable to continue to do so.
How are the Mortar Mixes Gauged?
The process of preparation of mortar paste is as follows:
1. The masonry mortar should be mixed only on a pucca platform made either with bricks, tin, or steel sheets.
2. The volume of material in each batch should be accurately proportioned.
3. When all the volumes of the materials for the mix have been measured, they are blended dry. For thorough mixing by hand, the mix should be turned over three times dry. Turning overtakes the form of moving all the material to one side with a shovel, moving it back, and then moving it to one side again. The mix should be of uniform color with no lumps or pockets of aggregate or binder at this stage.
4. A hollow like a volcano crater is made at the top of the pile and the water is added.
5. The dry material is then mixed with the water, starting with the inside of the ring. When enough water has been incorporated to make the mortar mix of the right workable consistency, the process of turning over is again performed three times wet.
Important Points to be Considered While Gauging for Obtaining a Good Mortar Mix
Water should not be added until the sand-cement mix is uniform in colour.
If water is added to the sand-cement mix, then it should be consumed within an hour, because the initial setting time of cement is about 30 minutes.
The mortar or the concrete should be mixed only on a steel or timber platform. Otherwise, the cement will be washed away with water.
How Long can the Mortar be Kept Before Using?