Mortar can be defined as a paste made by mixing fine particles (sand) and binding material (lime, cement etc) with water. Strength, establishment of a good connection with building components, and resistance to weathering are the primary features of hardened mortar, while mobility, placability, and water retention are the typical features of green mortar mixtures.
Furthermore, the mortar should be inexpensive and long-lasting and it should not impair the durability of the building units with which it comes into touch. There should be no cracks in the mortar joints.
Characteristics of Good Mortar
Below mentioned are some of the important characteristics of good mortar.
- Strength
- Mobility and placeability
- Resistance to rain penetration
- Water retention
Strength
Masonry’s strength is determined by the mortar as well as the construction unit (brick, stone, or block). A strong mortar will be useless if the building units are weak. It’s also worth considering whether full strength is required in a short period of time.
When the strength of lime or cement mixes develops slowly in cold weather, the choice of mix is likely to be influenced. Strong cement mortars are more likely to cause shrinkage cracks, thus they should be avoided unless a high level of strength is required.
On the other side, using a much weaker mortar, such as a 1:10 cement mortar, is unsuitable since the lower cement concentration results in reduced workability, cohesiveness, and porous joints with low frost protection.
The activity of binding materials, the water-cement ratio, binding material consumption, and sand quality all affect the strength of hardened mortar.
Also Read : Different Types of Mortar Used in Construction
Mobility and Placeability
The term “mobility” refers to the mortar’s consistency. The ease with which the mortar mix can be put in a thin and uniform layer on the surface at a low cost is referred to as placeability.
A mortar’s consistency can range from firm to fluid depending on its composition. Mortars for masonry, finishing, and other projects are manufactured movable enough. The placability of a mortar mix is determined by its mobility.
Mortars made only of Portland cement are usually weak in cement paste, stiff and non-placeable, therefore plasticizers are frequently included to compensate or increase its strength.
Resistance to Rain Penetration
The plastering mortar should form an impervious coating to protect the masonry joints and units. It is necessary to ensure a good bond between the building units, mortar and plaster.
Water Retention
It is distinguished by the capacity of mortar to maintain enough humidity in a thin layer distributed over a porous substrate and avoid stratification during transit. After setting, a mortar mix with low water retention will reveal the defects.
Mortar may lose so much water that the remaining water is insufficient to harden and provide the requisite strength. To improve water retention, mineral and organic substances might be used.