Monday, 2 October 2017

Cement Mortar

Mortar is a material used in masonry construction to fill the gaps between the bricks and blocks used in construction. Mortar is a mixture of sand, a binder such as cement or lime, and water and is applied as a paste which then sets hard.

Puzzolana Portland cement and sulphate-resisting cement form mortar which are used for constructions exposed to aggressive and waste waters. Cement mortars are used for plastering, rendering smooth finishes and damp proof courses. 

The mix proportions of cement mortar are given in Table below 


Preparation:-Manual mixing is applied for Small quantities of mortar; mechanical mixers are used for large quantities. 

For manual mixing,sand is sieved, cleaned with water to remove dirt and dust and dried. This dry sand is laid uniformly, on a pucca platform, over which cement is uniformly spread. The whole mass is then thoroughly mixed with spades till it becomes uniform in colour. A depression is then made in the middle of the mix and required quantity of water is added. The dry mix from the sides is moved and placed on the edges of the depression formed till the water is completely absorbed by the mix. The wet mix is then worked with spades to give a uniform consistency to the mortar.

For mechanical mixing the calculated quantity of cement, sand and water are fed into the cylindrical container of the mixer. A rotar with blades, inside the container, rotates and thoroughly mixes the ingredients. 
  
Precautions:-Basic property of Cement mortar should be uniformity and workability. It should be consumed within 30 minutes from the instant of adding water to the mix. The bricks, stones and blocks should be fully saturated in water before laying. The masonry and plastered or pointed surface should be kept completely wet by sprinkling water for at least 7 days. 

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