Preparation of Mortar

For proportioning along with cement mortar the unit of measurement is a cement bag of 50 kg whose volume is taken as 0.35 cu m. Although measuring sand, allowance should be provided for bulking (that is the phenomenon of increase within the volume of sand in the presence of moisture). The amount of bulking could be determined through making use of the fact which the volume of inundated sand is the similar as that of the dry sand. To search bulking, pour the sand up to the 200 ml mark of a 250 ml measuring cylinder. Then fill the cylinder along with water and stir well. It will be seen in which the sand surface is now below its original level. Assume the surface is at the mark - Y ml, the percentage of bulking is [200 - Y/Y] × 100.

                 Table: Relationship Between Moisture Content and Percentage of Bulking for Practical Guidance

Mixing of mortar should be preferably completed in a mechanical mixer. Cement mortar shall be used inside 30 minutes of mixing. Mixing lime putty, sand and surkhi and grinding it either manually or in a mechanical mortar mill commonly make lime mortar. Since a rule lime mortar shall be used on the similar day it is made. For lime cement mortar, lime putty and sand shall be ground in a mill and the needed quantity taken out and mixed thoroughly along with the specified quantity of cement within a mechanical mixer.

In view of simple availability of cement, convenience in use, uniformity of quality and the difficulty in acquiring lime of good and consistent quality, as well as the cumbersome procedure of preparation of lime putty etc., the common practice within the country is to use cement mortar in masonry.