Importance of mortar in brickwork construction
In brickwork construction, different types of mortars like M1, M2 etc. are applied. Normally, lime mortar and cement mortar are frequently utilized for brickwork. The characteristics, strength and applications of these mortars are discussed below :-
Consideration should given on the following factors for Mortar in Brickwork Construction :-
1. The strength of brickwork is not affected by the grade of the mortar used, i.e. several mortar mixes of diverse grades like M1 and M2 contain dissimilar strengths, but the strength of brickwork is not compromised. As for instance, mortars of mix ratios 1:6 and 1:4 provide equivalent strength of brickwork with the similar type of bricks, while they contain different strengths. It signifies that the strength of brickwork is based on the strength of bricks.
2. If the mortar mix ratio of 1:3 is applied for cement to sand or (cement + lime) to sand ratio, a solid mortar is produced with less voids.
3. Benefits of Lime Mortar – As the strength of lime mortar is under cement mortar, inclusion of lime in mortar brings the following benefits:
• Shrinkage in mortar is fewer, thus less susceptible to cracks because of shrinkage.
• The workability and plasticity of the mortar mix is enhanced with lime.
• Lime contains superior water retention strength and does not vaporize rapidly. Besides, dry bricks can’t absorb water from the lime mortar.
• Lime raises the volume of mortar and fills the voids so that it becomes water resistant against rain infiltration.
• Lime mortar can bond with bricks efficiently.
• Cement-lime mortar is more flexible and can adjust the normal movements of brick masonry without causing cracking. So, normally, cement lime mortar less susceptible to cracking as compared to cement mortar.
4. Lime mortar attains strength gradually and contains lower ultimate strength as compared to cement mortar. Besides, lime mortar with hydraulic lime can get superior and early strength. Lime mortar with fat lime does not consolidate at all in wet locations. While applying fat lime, some pozzolanic materials like burnt clay should be utilized instead of sand to enhance the strength of mortar.
5. Cement-lime mortar of leaner mixes from ratio 1:4 to 1:8 becomes rough specifically when the sand is coarse and not graded. Consequently, plasticizers should be utilized for better workability and plasticity of the mortar.
6. The strength of cement mortar is impacted by the following factors for the same ratio of cement and sand:
a. Grading of sand
b. Fineness and coarseness of sand
c. Angularity and roundness of the sand particles
7. If fineness of sand is raised, the workability of the cement-mortar mix is also increased. On the other hand, the surface area of the sand is also increased for which requirement for cement and water quantity for the same strength is also increased.
The strength will be reduced when the cement quantity is not raised. To attain the required workability, adequate water is necessary. This condition raises the water-cement ratio and as a result the strength is decreased.
8. Curing plays an important role to attain the maximum strength as well as maximum coating of the obtainable cement around sand particles.
9. Mortar beyond a mix ratio of 1:3 should not be applied in brickwork masonry construction due to high shrinkage and no considerable increase in strength of masonry, although the strength of mortar itself raises.
10. Overly thick joints decrease the strength of the brickwork.
11. Inclusion of pozzolana enhances the strength of the mortar as well as resistance capacity against chemical attacks.