3.1 General
The materials used in masonry construction shall be in accordance with Part 5 ‘Building Materials’ of the Code. Storage of materials shall be in accordance with good practice [6-4(1)].
3.2 Masonry Units
Masonry units used in construction shall conform to accepted standards [6-4(2)].
3.2.1 Masonry units may be of the following types:
a) Common burnt clay building bricks,
b) Burnt clay fly ash building bricks,
c) Pulverized fuel ash lime bricks,
d) Stones (in regular sized units),
e) Sand-lime bricks,
f) Concrete blocks (solid and hollow),
g) Lime based blocks,
h) Burnt clay hollow blocks,
j) Gypsum partition blocks,
k) Autoclaved cellular concrete blocks,
m) Stabilized soil blocks, and
n) Concrete stone masonry blocks. NOTES
1 Gypsum partition blocks are used only for construction of non-load bearing partition walls.
2 Use of other masonry units such as precast stone blocks, fly-ash-lime-gypsum bricks, stabilized soil blocks and other bricks/blocks not covered by the above specifications may also be permitted based on test results.
3.2.2 Masonry units that have been previously used shall not be reused in brickwork or blockwork construction, unless they have been thoroughly cleaned
and conform to this Section for similar new masonry units.
3.3 Mortar
Mortar for masonry shall conform to good practice [6-4(3)].
3.3.1 Minimum compressive strength for different grades of mortar on the basis of mix proportions as per 3.3.2 are given in Table 1.
| Sl No. | Grade of Mortar | Minimum Compressive Strength at 28 Days N/mm |
|---|---|---|
| (1) | (2) | (3) |
| i) | H1 | 10 |
| ii) | H2 | 6.0 |
| iii) | M1 | 5.0 |
| iv) | M2 | 3.0 |
| v) | M3 | 1.5 |
| vi) | L1 | 0.7 |
| vii) | L2 | 0.5 |
3.3.2 Mix proportions and compressive strengths of some of the commonly used mortars are given in Table 2.
3.4 Durability Criteria for Selection of Masonry Mortars
3.4.1 The selection of masonry mortars from durability considerations shall cover both the loading and exposure conditions of the masonry. The requirements for masonry mortar shall generally be as given in 3.4.2 to 3.4.6 (see also Table 1).
PART 6 STRUCTURAL DESIGN — SECTION 4 MASONRY
| Sl No. | Mix Proportions(By Mass) | Minimum Compressive Strength at 28 Days in N/mm (with Cement Compressive Strength at 28 Days, in N/mm , Between 33 and 43) | Minimum Compressive Strength of Cement : Sand Mortar at 28 Days in N/mm (with Cement Compressive Strength at 28 Days, in N/mm ≥ 43) | ||||
| Cement | Lime | Lime - Pozzolana Mixture | Pozzolana | Sand | |||
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) |
| 1 | 1 | C or B | 0 | 0 | 3 | 10 | — |
| 2(a) | 1 | C or B | 0 | 0 | 4 | 7.5 | — |
| 2(b) | 1 | C or B | 0 | 0 | 6 | — | |
| 2(c) | 1 | 0 | 0 | 0 | 4 | 6 | 7 |
| 3(a) | 1 | 0 | 0 | 0 | 5 | 5 | 6 |
| 3(b) | 1 | 1 C or B | 0 | 0 | 6 | 3 | — |
| 3(c) | 0 | 0 | 1(LP-40) | 0 | 3 | — | |
| 4(a) | 1 | 0 | 0 | 0 | 6 | 3 | 4 |
| 4(b) | 1 | 2B | 0 | 0 | 9 | 2 | — |
| 4(c) | 0 | 1A | 0 | 0 | 2 | 2 | — |
| 4(d) | 0 | 1B | 0 | 1 | 1 | 2 | — |
| 4(e) | 0 | 1 C or B | 0 | 2 | 0 | 2 | — |
| 4(f) | 0 | 0 | 1(LP-40) | 0 | 2 | — | |
| 5(a) | 1 | 0 | 0 | 0 | 7 | 2 | 3 |
| 5(b) | 1 | 3B | 0 | 0 | 12 | 1.5 | — |
| 5(c) | 0 | 1A | 0 | 0 | 3 | 1.5 | — |
| 5(d) | 0 | 1B | 0 | 2 | 1 | 1.5 | — |
| 5(e) | 0 | 1 C or B | 0 | 3 | 0 | 1.5 | — |
| 5(f) | 0 | 0 | 1(LP-40) | 0 | 2 | 1.5 | — |
| 6(a) | 1 | 0 | 0 | 0 | 8 | 1 | 2 |
| 6(b) | 0 | 1B | 0 | 1 | 2 | 0.7 | — |
| 6(c) | 0 | 1 C or B | 0 | 2 | 1 | 0.7 | — |
| 6(d) | 0 | 0 | 1(LP-40) | 0 | 0.7 | — | |
| 6(e) | 0 | 0 | 1(LP-20) | 0 | 0.7 | — | |
| 7(a) | 0 | 1B | 0 | 0 | 3 | 0.5 | — |
| 7(b) | 0 | 1 C or B | 0 | 1 | 2 | 0.5 | — |
| 7(c) | 0 | 0 | 1(LP-7) | 0 | 0.5 | — | |
1 Sand for making mortar should be well graded. In case sand is not well graded, its proportions shall be reduced in order to achieve the minimum specified strength.
2 For mixes in Sl No. 1 and Sl No. 2, use of lime is not essential from consideration of strength as it does not result in increase in strength. However, its use is highly recommended since if improves workability.
3 For mixes in SI No. 3(a), 4(a), 5(a) and 6(a) either lime C or B to the extent of part of cement (by mass) or some plasticizer should be added for improving workability.
4 For mixes in Sl No. 4(b) and 5(b), lime and sand should first be ground in mortar mill and then cement added to coarse stuff.
5 It is essential that mixes in Sl No. 4(c), 4(d), 5(d), 5(e), 6(b), 6(c), 7(a) and 7(b) are prepared by grinding in a mortar mill.
6 A, B and C denote eminently hydraulic lime, semi-hydraulic lime and fat lime respectively, as specified in appropriate standards listed in Part 5 'Building Materials' of the Code.
3.4.2 In the case of masonry exposed frequently to rains and where there is further protection by way of plastering or rendering or other finishes, the grade of mortar shall not be less than M3 but shall preferably be of grade M2. Where no protection is provided, the grade of mortar for external walls shall not be less than M2.
3.4.3 In the case of load bearing internal walls, the grade
of mortar shall preferably be M3 or more for high durability but in no case less than L1.
3.4.4 In the case of masonry in foundations laid below damp-proof course, the grades of mortar for use in masonry shall be as specified below:
a) Where soil has little moisture, masonry mortar of grade not less M3 shall be used.
b) Where soil is very damp, masonry mortar of grade preferably M2 or more shall be used. But in no case shall the grade of mortar be less than L1 and M3; and
c) Where soil is saturated with water, masonry mortar of grade M1 shall be used but in no case shall the grade of mortar be less than M2.
3.4.5 For masonry in buildings subject to vibration of machinery, the grade of mortar shall not be less than M1.
3.4.6 For parapets, where the height is greater than three times the thickness, the grade of masonry mortar used shall not be less than M1. In the case of low parapets, the grade of mortar shall be the same as that used in the wall masonry below.
3.4.7 The grade of mortar for bedding joints in masonry with large concrete blocks shall not be less than M1.
NOTE — For earthquake design consideration, recommended mortar mixes shall be as per Table 14.