MASONRY-Bridges nCulverts
Masonry is one of the main items of construction in a Bridge, Culvert, retaining walls, drains, abutments etc., and needs special care for ensuring quality control.It comprises masonry units such as brick, stone or concrete block laid in mortar.
TYPE OF MASONRY
The type of masonry used for structures shall be random rubble (coursed or un-coursed) or coursed rubble (first sort) or concrete block. For bridge works, generally coursed rubble masonry shall be used. The actual type of masonry used for different parts of structure shall be as specified in the Drawing.
MASONRY MORTARS
1. Materials
1.1 Cement
Cement of any of the following types shall be used meeting the physical requirementsgiven in table.
Type |
Grade |
Code |
Ordinary Portland cement |
33 |
IS: 269 |
Ordinary Portland cement |
43 |
IS: 8112 |
Ordinary Portland cement |
53 |
IS: 12269 |
Blast furnace slag cement |
- |
IS: 455 |
Portland pozzolana cement |
Fly-ash based |
IS:1489-Part I |
Portland pozzolana cement |
Calcined clay based |
IS:1489-Part II |
Sulphate resistant Portland cement* |
|
IS:12330 |
Use in masonry structures which are likely to be affected by the presenceof sulphates in surrounding soil or in ground water in concentration of0.2% and 0.03% respectively.
1.2 Sand
Sand or manufactured sand produced by crushing rock/gravel or a combination ofthe above shall consist of hard, durable and clean particles of natural sand, crushedgravel, or suitable combinations thereof and shall conform to the requirements givenin IS: 2116 and IS: 383 for sand and stone dust respectively.
2. Requirements
2.1 Workability
For laying walls with solid bricks : 90-130 mm.
For laying with perforated bricks : 70-80 mm.
For filling cavities : 130-150 mm.
2.2 Consistency and water retentivity
Table: Consistency and water retentivity of mortars for masonry works.
Property |
Work |
Recommended Values |
Consistency | Laying of solid brick walls | 90-130 mm |
Filling cavities | 130-150 mm | |
Water retentivity |
Masonry work with high |
More than 70% of flow |
(Flow of suction) | suction characteristics | before suction |
2.3 Rate of stiffening
Stiffening of mortar in masonry is caused either by loss of moisture or by thesetting action of binder used in the mortar or by both.
2.4 Strength
2.5 Resistance to rain penetration
2.6 Durability requirements
Table: Grade of Masonry Mortar
Sl. No |
Grade |
Compressive Strength at 28 days in MPa |
Cement |
Pozzolana (Fly Ash) |
Sand |
1 |
MM 0.7 |
0.7 to 1.5 |
1 |
- |
8.0 |
2 | 1 | 0.4* | 10.0 | ||
3 |
MM 1.5 |
1.5 to 2.0 |
1 |
- |
7.0
|
4 | 1 | 0.4* | 8.75 | ||
5 |
MM 3 |
3.0 to 5.0 |
1 |
- |
6.0 |
6 | 1** | 0.21 | 4.2 | ||
7 | 1 | 0.4* | 7.5 | ||
8 |
MM 5 |
5.0 to 7.5 |
1 |
- |
5.0 |
9 | 1 | 0.4 | 6.25 | ||
10 | 1 | 0.4 | 5.0 | ||
11 |
MM 7.5 |
7.5 & above |
1 |
- |
4.0 |
12 | 1** | 0.2 | 2.1 | ||
13 | 1 | - | 3.0 | ||
14 | 1 | 0.4 | 3.75 |
*Pozzolana with minimum lime reactivity of 4 MPa.
**This ratio by volume corresponds approximately to cement pozzolanaratio of 0.8:0.2 by weight.
In this case, only ordinary Portland cement is tobe used (IS: 269).
In case of masonry exposed frequent to rain and where there is furtherprotection by way of plastering or rendering or other finishes, the grade ofmortar shall not be less than MM 0.7, but shall preferably be of grade MM 2.0.
Where no protection is provided, the grade of mortar for external wall shall notbe less than MM 2.0.
In case of load bearing internal walls, the grade of mortar shall preferably beMM 0.70 or more for high durability, but in no case less than MM 0.5.
In the case of masonry work in foundations laid below damp proof course,when soil has little moisture, masonry mortar of grade not less than MM 0.7shall be used.
Where soil is very damp, masonry mortar of grade preferably MM 2.0 or moreshall be used. But in no case shall the grade of mortar be less than MM 2.0.
For masonry in building subject to vibration of machinery, the grade of mortarshall not be less than MM 3.0.
For parapets, where the height is greater than thrice the thickness, the grade ofmasonry mortar shall not be less than MM 3.0.
In case of low parapets, the grade of mortar shall be the same as used in thewall masonry.
The grade of mortar for bedding joints in masonry with large concrete blocksshall not be less than MM 3.0.
2.7 Curing
2.8 Quality control tests for masonry mortar
Material |
Test |
Code |
Frequency of testing / Min Quantity of Material for carrying out the test |
Water |
i) pH Value ii) Limits of Acidity iii) Limits of Alkalinity iv) Percentage of solids: a) Chlorides b) Suspended matter c) Sulphates d) Inorganic solids e) Organic solids |
IS: 3025 |
Water from each source shall be got tested before the commencement of work and thereafter once in every three months till the completion of the work. Water from municipal source need to be tested only once in six months. Number of tests for each source shall be 3. |
Cement |
Physical requirements: i) Fineness
ii) Soundness
iii) Setting time (Initial & Final) iv) Compressive strength v) Consistency of standard cement |
IS:4031 (Part 2) IS: 4031 (Part 3) IS: 4031 (Part 5) IS: 4031 (Part 6) IS: 4031 (Part 6) |
Each Lot / Every 50 tonnes or part thereof. Each brand of cement brought to site shall be tested as per this frequency. For sample lot less than 50 bags these tests need not be insisted. |
Sand |
paste Deleterious constituents |
IS: 2386 (Part 2) |
Every 20 m3 or part thereof or more frequently as decided by theEngineer. |
|
Silt Content |
IS: 2386 (Part 1) |
-do- |
|
Gradation |
IS: 2386 (Part 1) |
40 m3 or part thereof. |
|
Bulking |
IS: 2386 (Part 3) |
Every 20 m3 or partthereof or more frequently as decided by the Engineer. |
3. BRICK MASONRY
First class bricks of any of the following two types shall be used in masonryworks:
Types of bricks
3.1 Burnt clay bricks
Compressive strength of brick depends on type of soil used for moulding brick,method of moulding, technique of burning, etc. Strength of common brick availablegenerally varies from 2.5 to 25 MPa.
3.2 Burnt clay perforated building brick
It has the advantage over common brick of lightness in weight and better thermalinsulation. Therefore it is used in load bearing walls as well as non-load bearingpartitions and panels, where better thermal insulation and/or lightness in weight arerequired.
3.3 Burnt clay hollow block
It’s properties and use are similar to perforated brick, except that percentage of voidsis higher and thus masonry constructed with this unit is much lighter in weight. Itscompressive strength is however low and thus this unit is mainly used for non-loadbearing walls.
3.4 Classification
Bricks shall be classified on the basis of their minimum compressive strength as givenin table.
Class designation |
Average compressive strength |
|
Not less than |
Less than |
|
MPa (kgf/cm2 ) |
MPa (kgf/cm2 ) |
|
12.5 (125) |
12.5 (125) |
15 (150) |
10 (100) |
10 (100) |
12.5 (125) |
7.5 (75) |
7.5 (75) |
10 (100) |
5 (50) |
5 (50) |
7.5 (75) |
3.5 (35) |
3.5 (35) |
5 (50) |
3.5 Physical requirements The physical requirements of bricks for masonry works
Sl. No |
Item |
Requirements |
1 |
Minimum compressive strength |
Value specified in drawing or 7 MPa whichever is higher. |
2 |
Water absorption` |
Up to 20% by weight (IS: 3495-Part 2). |
3 |
Efflorescence |
‘Moderate’ up to 50% of exposed area of brick covered with a thin deposit of saltbut unaccompanied by powdering or flaking of surface (IS: 3495-Part 3). |
4 |
Preferred nominal size |
190 x 90 x 90 mm or 230 x 110 x 70 mm |
3.6 Construction
The following shall be ensured while carrying out brick masonry work.
Soak all bricks for a minimum period of one hour before use and remove fromtank sufficiently in advance so that they are skin dry before actual laying.
Lay all brickwork in English bond, unless otherwise specified, even and true toline, plumb or specified batter and level. Break all joints in successive coursesand lay joints accurately.
Lay all bricks with frogs up, if any, on a full bed of mortar. Slightly press thebricks so that the mortar gets into all hollow space of bricks to ensure properadhesion. Flush all joints and pack with mortar, to fill all hollow spaces.
Build brickwork in uniform layers so that no part of brickwork shall rise morethan one metre above the general construction level, to avoid unequalsettlement and improper jointing.
Remove all loose bricks and mortar while joining partially set or entirely setbrick masonry with new one. To achieve proper bond, roughen and wet withcement slurry. In case of vertical and inclined joints, achieve proper bond byinter-locking the bricks.
Tool all joints on exposed faces to give a concave finish, the thickness of jointnot exceeding 10 mm.
Keep masonry work in cement mortar constantly moist on all faces for aminimum period of seven days. Leave the top of masonry work flooded withwater at the close of the day. During hot weather, wet or cover all finished orpartly completed work to prevent rapid drying of brickwork. Maintain wateringand curing at the close of day’s work or for other period of cessation of works.
Erect single scaffolding for plastering, pointing and any finishing in which oneend of the put-logs/pole shall rest in the hole provided in the header course ofbrick masonry. Provide double scaffolding having two independent supportsclear of the work when brick work is exposed and not to be finished.
3.7 Sampling and testing
Samples of bricks shall be subjected to the following tests:
i) Dimensional tolerance.
ii) Water absorption.
iii) Efflorescence.
iv) Compressive strength.
3.8 Sampling from a stack
The samples shall be taken as below:
Scale of sampling and permissible number of defectives for visual and dimensional characteristics
No. of bricks in the lot |
For visual characteristics specified for individual bricks |
For dimensional characteristics for group of 20 bricks |
||
No. of bricks to be selected |
Permissible no of defective bricks in the sample |
No. of bricks to be selected |
Tolerance limit |
|
2001-10000 | 20 | 1 | 40 | - |
10001-35000 | 32 | 2 | 60 | |
35001-50000 | 50 | 3 | 80 |
NOTE: In case the lot contains 2000 or less bricks, sampling shall be asper the direction of the Engineer.
Scale of sampling and permissible number of defectives for physical characteristics
Lot size |
Sample size for compressive strength, water absorption and efflorescence |
Permissible number of defectives for efflorescence |
Warpage |
|
Sample size |
Permissible number of defects |
|||
2001-10000 |
5 |
0 |
10 |
0 |
10001- 35000 |
10 |
0 |
20 |
1 |
35001- 50000 |
15 |
1 |
30 |
2 |
NOTE: In case the lot contains 2000 or less bricks, sampling shall be as perdecision of the Engineer.
3.9 Criteria for visual characteristics
3.10 Criteria for dimensional characteristics
3.11 Criteria for physical characteristics
3.12 Tolerance limits
Permissible values of workmanship and tolerances for bricks and brick masonry aregiven in table
Table :Workmanship and tolerances for bricks and brick masonry.
Item |
Permissible value |
Dimensions of bricks |
±5% in size |
Compressive strength of bricks |
+2.5 MPa (No negative tolerance) on value specified or 7 MPa whichever is higher. |
Thickness of joints for general brick work |
Not more than 10 mm |
Thickness of joints for Arches |
5 mm to 15 mm |
Plaster finish thickness by more than 3 mm |
Surface thickness, not less than specified. |
3.13 Quality control tests
The Quality Control checks on bricks shall be as given in table.
Table: Quality Control tests for bricks masonry
Test /Check |
Code |
Frequency |
Colour and dimensional check |
IS: 5454 |
As per table 400-7. |
Water absorption |
IS: 3495 (Part 2) |
As per table 400-8. |
Efflorescence |
IS: 3495 (Part 3) |
As per table 400-8. |
Compressive strength |
IS: 3495 (Part 1) |
As per table 400-8 |
Some of the simple tests to fairly assess the quality of bricks are given below:
The tests to be carried out during construction are indicated in tablebelow:
Table: Quality Control tests during construction
Item of work |
Test /check |
Frequency |
Bond and plumbness |
English bond, verticality by plumb bob. |
For each course. |
Laying in mortar |
Laying in full bed of mortar with proper lapping. |
-do- |
Individual course |
Height of course and Joint thickness- (IS: 2212). |
-do- |
Top of coping (If provided) |
Sloping to drain off water. |
Daily. |
Mortar for joints* |
Mix proportions (Control on quantity of cement/lime by weight). |
Each batch. |
|
Consistency and water retentivity (IS: 2250). |
As required, at close intervals. |
|
Compressive strength (IS: 2250). |
On a set of 3 cubes where specified. |
Arches (Additional tests) |
Dimensions of abutment-pier for multiple arches (IS: 2118). |
Regularly. |
|
Centering for arch. |
For each span. |
|
Compaction and thickness of filling material over crown and haunches. |
Regularly. |
|
Thickness of joints. |
Regularly. |
Weep holes |
Location, size and spacing. |
For each work. |
Structural components |
Thickness, dimensions and laying. |
For each work. |
4. CONCRETE BLOCK MASONRY
4.1 General
4.2 Dimensions and tolerances
4.3 Classification of concrete blocks
Concrete blocks are either hollow (Open and closed cavity) load bearing concreteblocks, hollow (Open and closed cavity) non-load bearing concrete blocks or solidload-bearing/non-load bearing concrete blocks.
i) Grade A - Hollow concrete Blocks (Open and closed cavity): These are used asload bearing units and shall have a minimum block density of 15 kN/m3.
These shall be manufactured for minimum average compressive strength of3.5, 4.5, 5.5,7,0, 8.5, 10.0, 12.5 and 15.0 MPa respectively at 28 days asgiven in table (Ref: Table 2 of IS: 2185 Part 1).
ii) Grade B - Hollow concrete Blocks (Open and closed cavity): These are alsoused as load bearing units and shall have a block density between 11kN/m3 and 15 kN/m3. These shall be manufactured for minimum averagecompressive strength of 3.5 and 5.0 MPa respectively at 28 days as given intable (Ref: Table 2 of IS: 2185 (Part 1)).
iii) Grade C - Solid concrete blocks: These are used as load bearing units andshall have a block density not less than 18 kN/m3. These shall bemanufactured for minimum average compressive strength of 4.0 and 5.0MPa respectively as given in table (Ref: Table 2 of IS: 2185 (Part 1)).
Type |
Grade |
Density of block kN/m3 |
Minimum average compressive strength of units, MPa |
Minimum compressive strength of individual units, MPa |
Hollow (Open and closed cavity) load bearing unit |
A (3.5) |
Not less than 15.0 |
3.5 |
2.8 |
A (4.5) |
4.5 |
3.6 |
||
A (5.5) |
5.5 |
4.4 |
||
A (7.0) |
7.0 |
5.6 |
||
A (8.5) |
8.5 |
7.0 |
||
A (10.0) |
10.0 |
8.0 |
||
A (12.5) |
12.5 |
10.0 |
||
A (15.0) |
15.0 |
12.0 |
||
B (3.5) |
Less than 15.0 but not less than 11.0 |
3.5 |
2.8 |
|
B (5.0) |
5.0 |
4.0 |
||
Solid load bearing unit |
C (5.0) |
Not less than 18.0 |
5.0 |
4.0 |
C (4.0) |
4.0 |
3.2 |
4.4 Physical requirements
4.5 Marking
Concrete masonry units used shall satisfy the specifications and standards prescribedand shall have the following information marked permanently on them.
i) Identification of the manufacturer.
ii) Grade of the unit.
iii) Year of manufacture.
4.6 Quality control tests for cement blocks
5 STONE MASONRY
5.1 General
5.2 Requirements
Table: Physical requirements
Item |
Code |
Requirements |
Least dimension |
IS: 1597 (Part I) |
150 mm |
Water absorption in stone |
IS: 1124 |
5% of its weight. |
Dressing of stone |
IS: 1129 and IS: 1597 |
- |
Minimum height of individual course |
|
160 mm |
Consumption of mortar in stone masonry |
|
0.25 to 0.30 m3 for each m3 of stone masonry |
Table: Physical requirements of various types of stones
Type of stone |
Maximum water absorption % by weight |
Minimum compressive strength (MPa) |
Granite |
0.5 |
10.0 |
Basalt |
0.5 |
40.0 |
Lime stone ( Slab & tiles) |
0.1 |
20.0 |
Sand stone (Slab & tiles) |
2.5 |
30.0 |
Marble |
0.4 |
50.0 |
Quartzire |
0.4 |
80.0 |
Laterite (Block) |
12 |
3.5 |
5.3 Workmanship
The following shall be ensured while carrying out stone masonry work:
5.4 Simple field tests
Some of the requirements and simple tests are indicated below:
5.5 Quality control tests
Table: Quality Control tests prior to construction
Sl. No. |
Test /Check |
Code |
Frequency |
1 |
Shape and dimension |
IS: 1597 (Part 1) |
3 samples on receipt at site. |
2 |
Water absorption |
IS: 1124 |
3 samples on receipt at site. |
3 |
Dressing of stones via hearting, bond, quoin, face stones, headers etc. |
IS: 1129 |
One for each stock after selection for individual work. |
Table: Quality Control tests during construction
Materials/Work |
Test/Check |
Frequency/ Stage |
Bond and plumbness |
For stability and appearance with plumb bob |
While laying each course. |
Laying in mortar |
Horizontality of courses verticality and staggering of joints. |
-do- |
Mortar for joints |
i) Consistency and water retentivity (IS: 2250) |
As required. |
ii) Mix proportions for different works. |
Daily. |
|
iii) Compressive strength (IS: 2250). |
On a set of 3 cubes where specified. |
|
Individual course |
Height joint thickness and laying (IS:1597 (Part I & 2) and IS: 2212) |
-do- |
Arches (Additional checks) |
Centering and simultaneous commencement of work from both ends. |
Check during erection. |
Compaction and thickness of filling material over crown and haunches. |
As and when work is on hand. |
|
Erection of abutment pier for multiple arches. |
As and when such work is on hand. |
|
Thickness of joints. |
Check during construction |
|
Top of coping (If provided) |
Sloping to drain off water. |
Once on either side of parapet. |
Mortar |
Quality of mortar. |
For each component of work. |
Consumption per m3 of stone masonry work. |
-do- |
|
Weep holes |
Location, size and spacing |
For each work. |
Structural components |
Thickness, dimensions and laying. |
For each work. |
General workmanship |
Colour, aesthetics, elegance, pin headers, corner stones and plumbness etc. |
For each work. |
6 LATERITE MASONRY
6.1 General
6.2 Requirements
Table: Size of laterite stone blocks
Length(mm) |
Breadth(mm) |
Thickness(mm) |
390 |
190 |
190 |
490 |
190 |
190 |
590 |
290 |
290 |
Table: Physical properties of laterite stone blocks
Properties |
Code |
Requirement |
Water absorption |
IS: 1124 |
Not more than 12% by mass. |
Specific gravity |
IS: 1124 |
Not less than 2.5. |
Compressivestrength |
IS: 1121 (Part 1) |
Not less than 3.5 MPa. |
6.3 Workmanship
6.4 Sampling and testing
Table: Sampling and criteria for conformity
Number of blocks |
Number of blocks to be selected in the sample |
Permissible number of defectives |
Sub-sample size number |
Up to 100 |
5 |
0 |
3 |
101 to 300 |
8 |
0 |
3 |
301 to 500 |
13 |
0 |
6 |
501 above |
20 |
1 |
6 |
These blocks shall be first tested for compressive strength and then for waterabsorption and specific gravity. A lot shall be considered to have satisfied therequirements of physical properties, if none of the blocks tested for theserequirements fails in any of these tests.
RELATED CODES :
MoRTH-Specifications for Road and Bridge works (5th revision).
1.IS:269-Specification for 33 grade ordinary Portland cement
2.IS:383-Specification for coarse and fine aggregate from naturalsource for concrete.
3.IS:455-Specification for Portland slag cement.
4.IS:460-Specification for test sieves.
5.IS:650-Specification standard sand for testing of cement.
(Part 1)-Wire cloth test for sieves
6.IS:1121-Method of tests for determination of strength properties of natural building stones:
(Part 1)-Compressive strength.
7.IS:1124-Method of test for determination of water absorption,apparent specific gravity and porosity of natural buildingstones.
8.IS:1344-Specification for calcined clay Pozzolana.
9.IS:1489-Specification for Portland pozzolana cement.
10.IS:1542-Specification for sand for plaster.
11.IS:1727-Methods of test for pozzolanic materials.
12.IS:2116-Specification for sand for masonry mortar.
13.IS:2185-Concrete masonry units - specification.
14.(Part2250)-Code of practice for preparation and use of masonrymortar.
15.IS:2386-Method of test for aggregate for concrete:
(Part 1)-Particle size and shape.
(Part 2)-Estimation of deleterious materials and organic impurities.
(Part 3)-Specific gravity, density, voids, absorption and bulking.
16.IS:3025-Method of sampling and test for water.
17.IS:3115-Lime based blocks – specification.
18.IS:3406-Specification for masonry cement.
19.IS:3620-Specification for laterite stone block for masonry.
20.IS:3812-Specification for pulverized fuel ash:
(Part 2)-For use as pozzolana in cement, cement mortarconcrete.
21.IS:4031-Method of physical test for hydraulic cement.
22.IS:8041-Rapid hardening Portland cement.
23.IS:8042-Specification for white cement.
24.IS:8043-Hydrophobic Portland cement.
25.IS:8112-Specification for 43 grade ordinary Portland cement.
26.IS:11652-Woven HDPE sacks for packing cement.
27.IS:11653-Woven polypropylene sacks for packing cement.
28.IS:12174-Jute synthetic union bags for packing cement.
29.IS:12269-Specification for 53 grade ordinary Portland cement.
*****