Preparation of Lime Mortar

PREPARATION OF LIME MORTAR

Lime mortar is formed by mixing of lime, sand, and water. The required amount of lime and sand is placed on the ground or tray. The lime and sand are mixed evenly by turning the spades up and down. The water is added till the uniform color and consistency of the mortar area unit is obtained and also the mixture is persistent with spades.

The lime used for mortar could be either fat lime or hydraulic lime. Fat lime includes high burnt lime content. Its hardening depends on the loss of water and also the absorption of carbonic acid gas from the atmosphere and might be recrystallized at the correct time. When mixed with water it forms a putty or mortar that has the property of setting and hardening below water. Slacked fat lime is employed to form mortar for daubing, whereas hydraulic lime is employed for stone construction and is additionally suited to the development of chimneys and also the lightweight structure of buildings.

Also lime mortar mix ratio differs for various types of work. Lime mortar has high physical property and playability, sensible cohesion with alternative surfaces, and low shrinkage. They harden and develop strength, gaining strength endlessly for a protracted time. Fat lime and hydraulic limes are used for making lime mortar. If fat lime is used sand mixed is normally 2 to 3 times its volume. If hydraulic lime is used sand mixed is only 2 times the volume of lime. Lime is prepared by pounding, if quantity required is small or by grinding, if the required quantity is more.

Pounding: For pounding, pits are formed in hard grounds. The size of pit is usually 1.80 m long, 0.4 m wide and 0.5 m deep. It is provided with lining of bricks or stones. Lime and sand dry mixed with required proportion is placed in the pit. Small quantity of water is added at intervals. In each interval the mix is pounded with wooden pounders and mortar is turned up and down. The process is continued till uniform colour and desired consistency is achieved.

Grinding: The grinding may be carried out in bullock driven grinding mill or in power driven grinding mill. It consists of a circular trench of radius 3 to 4.5 m, 0.3 m wide and 0.4 m deep. A wooden shaft pivoted at centre carries a stone wheel of width just 50 mm to 100 mm less than that of trench. Bullocks drive this wheel in the trench for grinding mortar. The dry mix is placed in the trench. Water is added gradually and bullock driven stone wheels grind the mix. A worker turns the mix up and down regularly. This method of preparing mortar needs 6 hours and can produce about 1.7 m³ of mortar.

Power driven grinding mill: Two rollers rotate in a pan of diameter 1.8 to 2.4 m. Either pan or roller is rotated with the help of oil engine or electric power. During mixing required quantity of water is added gradually. Lime mortar is also having good grinding property. Fat lime mortar is used for plastering while hydraulic lime mortar is used for masonry construction. This mortar was considered cheap in olden days and was commonly used in small towns. However the combersome process of preparation and ease in availibility of cement in market has almost replaced the use of lime mortar.