Mortar

As you know various types of Mortar is formed by mixing, cement, lime or sand in definite proportions with water. 

Grade of Masonry Mortar 

The grade of masonry mortar should be defined by its compressive strength in N/mm2 at the age of 28 days as per standard procedure detailed in IS:2250-198 1. 

Lime Mortar 

Lime mortar should be prepared mixing lime putty or dry hydrated lime powder and sand in the specified proportions. Pozzolona may be added if specified. Dry volume of the ingredients should be considered. Lime putty if used should be prepared from fresh lumps of quick lime in tanks of water. Lime putty once prepared should be kept wet till it is used. It can be stored upto fifteen days if kept wet. 

Mixing  and Grinding 

Lime putty and sand with pozzolona if any in the specified proportions should he mixed on a water tight platform or in a trough. It should then be grinded by power driven mobile roller pan mixer conforming  to IS 2438-1963. For using manually driven or animal. 

Driven mortar mill mortar should be grounded by not less than 180 revolutions for a minimum of three hours to get a stiff paste of necessary working consistency. 

Where the mortar is to be prepared using dry hydrated lime powder, then ingredients should first be mixed dry in a mechanical mixer. Afterwards just sufficient quantity of water should be added to get mortar of required working consistency. Mixing should be done at least for three minutes  after adding water. 

When mechanical mixer is not available mixing may be allowed by manually operated mixer with the approval of the engineer in charge. Mixing time should be suitable increased in that case. 

Lime mortar should be used as soon as possible after mixing preferably on the same day. It should be kept wet by covering with wet jute bags or by any other suitable means and should never be allowed to dry.