Cement Mortar

Cement mortar is an intimate mixture of cement and sand mixed with sufficient water to produce a plastic mass. The amount of water will vary according to the proportion and condition of the sand, and had best be determined independently in each case. Sand is used both for the sake of economy and to avoid cracks due to shrinkage of cement in setting.

Properties of cement mortar are:

   1. When water is added to an intimate dry mixtures of cement and sand, hydration of cement starts and it binds sand particles and the surrounding surfaces of masonry and concrete.

   2. The strength of mortar depends upon the proportion of cement and sand.

PROPORTIONING Of CEMENT MORTAR

Strong and workable mortar is obtained if the ratio of cement and sand is between 1:3 to 1:6. However, the occasional use of 1:8. ratio is permitted. Strength and workability improve with the increase in cement content (rich mixes). However, mortars richer than 1:3 proportion are not used because of high shrinkage and no appreciable gain in strength. In case of lean mixtures, voids in the sand are not impervious.

Proportions recommended for various workers are as follows:

1.	Masonary works	1:6 to 1:8
2.	Plastering masonry	1:3 to 1:4
3.	Plastering concrete surface	1:3
4.	Pointing	1:2 to 1:3

USES OF CEMENT MORTAR

(1) To bind masonry units like stones, bricks and hollow cement blocks.

(2) To give impervious surface to roof slab and walls (plastering).

(3)To give neat finishing to concrete works.

(4) For pointing masonry joints.

(5) For preparing hollow blocks.

(6) As a filler material in ferro-cement works.