04-MASONRY



BUILDINGS-MASONRY

Masonry is one of the main items of construction in a building, 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.

MASONRY MORTARS

1. Materials

  1. Materials used for making mortars for masonry viz., cement mortars, limemortars and cement-lime mortars are
  1. Inert materials such as sand and crushed stone.
  2. Binder such as clay, lime and cement.
  3. Pozzolana such as fly ash, burnt clay/surkhi.
  4. Lime-pozzolana mixture.
  5. Plasticizers.
  1. Most of these materials are covered by Indian Standards. Cement-sand mortarshall in general conform to IS: 2250.

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

  1. The mix shall be workable. Workability shall be measured by recording depth ofpenetration of a standard cone as detailed in IS: 2250.
  2. Bureau of Indian Standards recommend the following values of penetration fordifferent purposes:

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

  1. Cement-sand mortar shall in general conform to IS: 2250 and its consistencyand water retentivity shall be determined as per BIS code. The recommendedvalues of consistency and water retentivity are given in table.
  2. A standard test for determination of water retentivity in masonry mortars isgiven in IS: 2250. In accordance with that standard, water retentivity ofmasonry mortar should not be less than 70%.

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.

  1. Cement mortar stiffens mainly through setting action of cement. In coldregions, when nights are frosty, it is important that mortar should stiffenrapidly enough so that it is not damaged by frost by formation of ice crystalswithin the body of mortar.
  2. For this reason, as a general rule, cement mortar shall not be leaner than 1:6and cement- lime mortar leaner than1:½:4½.
  3. In addition, some further precautions like preventing masonry units, sand andwater from getting too cold, use of warm water for mixing of mortar, use ofcalcium chloride as an accelerator in cement mortar, covering the freshly laidmasonry with tarpaulins at the close of the day’s work etc, should be taken.

2.4 Strength

  1. It is necessary that masonry shall attain the requisite strength by the timeloads are imposed on it. With that in view, 28-day strength of a mortar is takeninto consideration.
  2. The compressive strength shall be determined in accordance with theprocedure given in IS: 2250.
  3. When mud mortar is used in brick or stone masonry, basic stress in masonryshould be limited to 0.2 N/mm2
  4. Mud mortar should not be used in moist or wet situations like foundations of awall. This mortar is also not suitable for use in areas infected with white ants.

2.5 Resistance to rain penetration

  1. Rain water penetrates a masonry wall by three different modes:
  1. Through pores of masonry units.
  2. Through pores of mortar.
  3. Through cracks between units and mortar.
  1. From the view-point of rain penetration, bonding property of mortar is of greatimportance.
  2. Mixes of composite mortars in common use are 1:½:1½, 1:1:6, 1:2:9 and 1:3:12. Of these 4 mixes, 1:1:6 mix is in more common use since it hasreasonably good strength and also, imparts to masonry, adequate resistance torain penetration.

2.6 Durability requirements

  1. For attaining durability, frost action before the mortar has gained sufficientstrength shall be prevented.
  2. Mortar shall not be exposed to repeated cycles of freezing and thawing.
  3. The presence of soluble sulphates either in burnt clay bricks or in soil incontact with masonry in foundation adds to the process of deterioration.
  4. Ingress of moisture through cracks of masonry shall be avoided.
  5. The grades of masonry mortar shall be selected as specified in table (Ref:IS: 2250). The grade of masonry mortar will be defined by its compressivestrength in MPa at the age of 28 days as determined by the standard proceduredetailed in IS: 2250.

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).

  1. 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.

  2. Where no protection is provided, the grade of mortar for external wall shall notbe less than MM 2.0.

  3. 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.

  4. 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.

  5. 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.

  6. For masonry in building subject to vibration of machinery, the grade of mortarshall not be less than MM 3.0.

  7. For parapets, where the height is greater than thrice the thickness, the grade ofmasonry mortar shall not be less than MM 3.0.

  8. In case of low parapets, the grade of mortar shall be the same as used in thewall masonry.

  9. The grade of mortar for bedding joints in masonry with large concrete blocksshall not be less than MM 3.0.

2.7 Curing

  1. Curing of masonry shall begin as soon as partial set of mortar has taken place.
  2. Curing shall be continued up to a minimum period of 7 days from date oflaying of masonry, if Ordinary Portland Cement is used. In dry weather it shallbe extended up to 10 days.
  3. For Portland Pozzolana/slag cement, minimum curing period shall be 10 days.
  4. No curing is required in case of mud masonry, since there is no setting actionrequiring the presence of moisture.

2.8  Quality control tests for masonry mortar

  1. The cement mortar if unused for more than 30 minutes after addition of watershall be rejected and removed from site.
  2. The mix proportion of cement : sand can be checked as follows:
  1. Take about 200 gm of green cement mortar and add 100 ml of water in ameasuring jar and shake the contents well.
  2. Allow the contents to settle. While the sand gets deposited at the bottom,cement shall settle above.
  3. From the volumes of each, the approximate proportion of cement and sandcan be determined.
  1. Mortar consistency can be checked by the following:
  1. If a small quantity of mortar is dropped from a trowel, the trowel ought tobe left perfectly clean.
  2. A little mortar worked gently in the hands should be easily moulded into aball; on the surface of which water would appear.
  3. When the ball is dropped from a height of half a meter (500 mm) on a hardsurface, it must retain its rounded shape.
  1. The control tests for materials shall be as given in table.

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 the

Engineer.

 

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:

  1. Burnt clay bricks conforming to IS: 1077.
  2. Clay fly-ash bricks conforming to IS: 13757.

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

Minimumcompressive

strength

Value specified in drawing or 7 MPawhichever 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Tool all joints on exposed faces to give a concave finish, the thickness of jointnot exceeding 10 mm.

  7. 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.

  8. 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:

  1. The stack shall be divided into a number of real or imaginary sections and therequired number of bricks drawn from each section.
  2. For this purpose, bricks in the upper layers of the stack shall be removed toenable units to be sampled from places within the stack.
  3. For other methods of sampling i.e. sampling in motion and sampling fromlorries or trucks, IS: 5454 shall be referred.
  4. Scale of sampling and criteria for conformity for visual and dimensionalcharacteristics are given in table.

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

  • The bricks shall be selected and inspected for ascertaining their conformity tothe requirements of the relevant specification.
  • The number of bricks to be selected from a lot shall depend on the size of lotand shall be in accordance with table for visual characteristics, in allcases and dimensional characteristics, if specified for individual bricks.
  • If the number of defective bricks found in the sample is less than or equal tothe corresponding number as specified in table, the lot shall beconsidered as satisfying the requirements of visual characteristics. Otherwisethe lot shall be deemed as not having met the visual requirements.

3.10  Criteria for dimensional characteristics

  • The number of bricks to be selected for inspecting the dimensions andtolerance shall be in accordance with table.
  • The selected bricks will be divided into groups of 20 at random and each of thegroup of 20 bricks thus formed will be tested for all dimensions and tolerances.
  • A lot shall be considered having found meeting the requirements of dimensionsand tolerance if none of the groups of bricks inspected fails to meet thespecified requirements.

3.11  Criteria for physical characteristics

  • The lot which has been found satisfactory in respect of visual and dimensionalrequirements shall be next tested for physical characteristics like compressivestrength, water absorption, efflorescence as specified in relevant materialspecification.
  • The bricks for this purpose shall be taken at random from those alreadyselected above. The number of bricks to be selected for each of thesecharacteristics shall be in accordance with relevant columns of table.

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:

  1. In efflorescence test, a sample brick is soaked in water for 24 hours and itsappearance after removal from water shall be free from white patches, thetotal area not exceeding 50%. In case the surface area exhibiting patchesexceed 50% of total area, both the brick and water samples shall besubjected to further testing for ascertaining suitability.
  2. In water absorption test, a brick should not absorb more than one-fifth ofits dry weight after immersion in water for 24 hours.
  3. Bricks are considered good when clear ringing sound is heard when twobricks are struck against each other. A sample brick should not breakwhen dropped flat on hard ground from a height of about 1 m.
  4. Correct firing promotes toughness. The bricks should not be under-burnt.A well burnt brick when scratched with a finger nail should leave noimpression.

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

  1. Concrete blocks for use in masonry may be solid, hollow, lightweight orautoclaved cellular as per standard specifications
  2. The concrete blocks shall confirm to IS: 2185 (Part 1, 2 and 3) and IS: 3115.
  3. These are used for load bearing walls as well as non-load bearing panels andpartitions.
  4. Choice of blocks should be made carefully, taking into consideration type ofstructure, loads, climatic conditions, economy in cost, ready availability ofblocks etc.
  5. Concrete block masonry is very much prone to shrinkage cracks. Therefore, to avoid or minimize    cracks, blocks must strictly conform to standardspecifications and suggestions for handling, storage, moistening before use,selection of mortar for laying masonry, curing and finishing.
  6. Moreover, it should be ensured that concrete blocks are dried for a period of atleast 28 days after curing so that the blocks undergo initial shrinkage beforeuse in masonry work.

4.2 Dimensions and tolerances

  1. Concrete blocks shall be made in sizes and shapes to fit different constructionneeds. They include stretcher, corner, double corner or pier, jamb, header, bullnose and partition block and concrete floor units.
  2. Concrete block, hollow (Open or closed cavity) or solid shall be referred to by itsnominal dimensions. The term nominal means that the dimension includes thethickness of the mortar joint. Actual dimensions (length and depth only) shallbe 10 mm short of the nominal dimensions.
  3. The nominal dimensions of concrete block shall be as follows:
  1. Length : 400, 500 or 600 mm
  2. Height : 200 or 100 mm
  3. Width  : 50, 75, 100, 150, 200, 250 or 300 mm.
  1. Blocks of half length viz., 200, 250 or 300 mm which correspond to the fulllength brick may also be used wherever required. Full length and half-length U-blocks may also be used for the purposes of band and lintels.
  2. Blocks of sizes other than those specified above may also be used if theyconform to the quality standards prescribed in the relevant codes.

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.

  1. Hollow (Open or closed cavity) block: A block having one or more large holes orcavities which either pass through the block (open cavity) or do not effectivelypass through the block (closed cavity) and having the solid material between50% and 75% of the total volume of the block calculated from the overalldimensions.
  2. Solid block: A block which has solid material not less than 75% of the totalvolume of the block calculated from the overall dimensions.
  3. The concrete blocks shall conform to the following three grades as per IS: 2185(Part 1).

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

  1. All units shall be sound and free of cracks or other defects which interfere withthe proper placing of the unit or impair the strength or performance of theconstruction. Minor chipping resulting from the customary methods ofhandling during delivery, shall not be deemed grounds for rejection.
  2. Where units are to be used in exposed wall construction, the face or faces thatare to be exposed shall be free of chips, cracks, or other imperfections, exceptthat if not more than 5% of a consignment contains slight cracks or smallchippings not larger than 25 mm, this shall not be deemed grounds forrejection.

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

  1. The Contractor shall furnish the manufacturer’s test certificate for blockdensity, compressive strength, water absorption and drying shrinkage ofconcrete blocks, which shall conform to IS: 2185 (Part 1).
  2. The tests specified in clause (a) shall be carried out by the Contractor ifmanufacturer’s certificate is not furnished or the Engineer is not satisfied withthe manufacturer’s test certificate.
  3. The tests specified in clause (a) shall be carried out by the contractor, if thecement blocks are manufactured at Site.

5    STONE MASONRY

5.1 General

  1. Types of stones commonly used in building construction are granite, trap,basalt, quartzite, limestone and sand stone. Another type of stone which is asemi weathered rock namely laterite, though not very durable and strong, isused for small and low cost structures.
  2. There are three main varieties of stone masonry in common use namelyrandom rubble, coursed rubble and ashlar, with some further sub varietiesdepending upon quality of stone, standard of dressing and laying of stones,standard of finish and workmanship and architectural style.
  3. Stone for use in masonry should be hard, sound and free from weathering,decay, cavities, cracks, sand-holes, injurious veins, patches of loose or softmaterials.
  4. Stone should not contain cryptic crystalline silica or chert, mica, or otherdeleterious materials like iron oxide and organic impurities.
  5. Selection of stone is usually based on past experience, and in order to ensuredesired quality, it is customary to stipulate source of stone i.e., particulars ofquarries from which stone should be procured for use in a particular job.

5.2 Requirements

  1. The principal requirements of a building stone are strength, density anddurability. All stones other than those of sedimentary origin are suitable forstone masonry work.
  2. Use stone which is hard, sound, free from cracks, decay, weathering, defectslike cavities, flaws, sand holes and patches of loose or soft materials.
  3. Do not use stones with round surface.
  4. The Specifications and requirements of stones shall satisfy those given in table.

  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

  1. Normally use Coursed Rubble (CR) Masonry (First sort) for load bearingstructures, CR masonry (Second sort) for culverts, wing/return walls of smallbridges and Random Rubble (RR) Masonry for wing/return/toe walls of heightless than 3 m.
  2. The compressive strength of common types of stones shall be as per table and the percentage of water absorption shall generally not exceed 5% forstones other than specified in table.
  3. Test for compressive strength shall be carried out as per IS: 1121 (Part 1).
  4. Test for water absorption shall be carried out as laid down in IS: 1124   
  5.            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:

  1. The least dimension of the dressed stone shall not be less than 150 mm. Thestones shall be immersed in water for 24 hours before use. Only rectangularshaped bond stones or headers shall be used.
  2. The stones shall be laid on their natural beds in horizontal courses, height ofeach course shall be same.
  3. Height of construction in a day should not exceed 1.0 m so as to avoidexcessive load on fresh mortar. Connected masonry should be raised uniformlyall over. However, if one part of masonry is to be left behind, the wall should beracked at an angle not steeper than 45. Toothing in stone masonry should notbe allowed.
  4. Lay outer layers of masonry first, then fix the location of headers and bondstones and lay them. Lay the stones in the hearting, on their broadest face, toensure that spaces between stones are filled.
  5. Where there is variation in the height of the courses, place the larger courses atlower levels with the heights of courses decreasing gradually towards the top ofthe wall.
  6. In tapered walls, the beds of the stones and planes of courses shall be keptright angle to the batter. In case of piers with batter on both sides, keep thecourse horizontal.
  7. Lay all stones, fill mortar both in bed and vertical joints and settle carefully inplace with a wooden mallet immediately on placement before the mortar hasset.
  8. Before laying first course of stone masonry on rock, place concrete leveling course of M10 grade, average thickness 150 mm.
  9. In case any stone already set in mortar, is disturbed or the joint broken, take itout without disturbing the adjacent stones and joint. Reset the stone in freshmortar after removing dry mortar and thoroughly cleaning the stones andjoints.
  10. Use selected quoin stones and arrange to bond alternately long and short inboth directions.
  11. Provide sufficient transverse bonds by the use of bond stones or set of bondstones extending from the front to the back of the wall from outside to theinterior and vice versa, overlapping each other by 150 mm (Minimum).
  12. Make vertical joints truly vertical and staggered as far as possible. Keep thedistance between vertical joints of upper and lower layer, more than half theheight of the course.
  13. Masonry work over a concrete foundation block shall be done only after 48hours of casting.

5.4 Simple field tests

Some of the requirements and simple tests are indicated below:

  1. The stones should be hard, tough, compact grained and of uniform texture andcolour.
  2. They should be free from cracks, decay, weathering defects like cavities, flaws,veins, sand holes and patches of loose/soft material.
  3. Break a stone with a hammer. The surface of a freshly broken stone should bebright, clean and sharp and should show uniformity of texture without loosegrains and be free from any dull chalky or earthy appearance.
  4. If a drop of dilute hydrochloric acid or sulphuric acid on a piece of stone causeseffervescence, the stone contains weathering materials.
  5. A sample of stone when struck with a 1 kg hammer should emit a ringingsound and should not break with one blow.
  6. A pen-knife when scratched on surface should not make an impression on hardstone.

5.5 Quality control tests

  1. The Quality control tests on stones for masonry are given in table.

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.

  1. The Quality control tests during construction are given in table.

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

  1. The term laterite stone has been applied generally to a group of rocks, whichoccur as surficial blankets. It is the residual weathering products of certainrocks, containing silicates, such as basalt, granite and slate.
  2. The physical properties of this stone vary considerably from place to place.Freshly quarried laterite is soft and porous but when exposed to atmosphericconditions it hardens and makes a very tough material. Therefore, it is alwaysdesirable that these stones should be quarried sufficiently ahead of use. Butonly laterite stones of certain minimum physical properties are suitable formasonry construction and therefore, a careful selection in the procurement ofthis stone is necessary before use.

6.2 Requirements

  1. The stone blocks shall be without any soft veins, cracks, cavities, flaws andsimilar imperfections.
  2. The block shall be exposed preferably for a period of three months before beingused in the construction of masonry to ensure adequate stabilisation. However,exposure to rains should be avoided.
  3. The standard size of laterite stone blocks shall be as specified in table.

Table: Size of laterite stone blocks

Length(mm)

Breadth(mm)

Thickness(mm)

390

190

190

490

190

190

590

290

290

  1. Sizes other than those mentioned in table, may be supplied if approved  by the Engineer.
  2. Tolerance of ±5 mm shall be allowed on dimensions specified in table.
  3. The physical properties of the laterite stone blocks shall conform to therequirements given in table.

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

  1. The blocks shall be of uniform shape with straight edges at right angle.
  2. The edges of the block shall be rough and chisel dressed as prescribed in IS:1129.

6.4 Sampling and testing

  1. In any consignment all the blocks from the same quarry shall be groupedtogether to constitute a lot.
  2. Samples shall be selected and tested separately for each lot for determining itsconformity or otherwise to the requirements of the specification.
  3. The number of blocks to be selected for the sample shall depend upon the sizeof the lot and shall be in accordance with table.

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

  1. The blocks in the sample shall be selected at random and in order to ensure the randomness of selection, random number table may be used as per IS:4905.
  2. Any block failing in any one or more of the above requirements of physicalproperties shall be considered to be defective.
  3. A lot shall be considered as conforming to these requirements if the number ofdefectives obtained is not more than the permissible number of defectives givenin table.
  4. The lot having been found satisfactory with respect to general requirements,dimension and workmanship, shall be tested for physical properties. For thispurpose a sub-sample of size given in table shall be selected at random.

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 :

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.

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