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Brick masonry work and it's Tolerance limits ( Specifications of Brick masonry)


This article includes Brick masonry work and it's Tolerance limits ( Specifications of Brick masonry, type of brick masonry and its measurements )



TERMINOLOGY

Bond

The arrangement of the bricks in successive courses to tie the brick work together both longitudinally and transversely. The arrangement is usually designed to ensure that no vertical joint of one course is exactly over the one in the next course above or below it, and there is greatest possible amount of lap.

Bed Joint
Horizontal joint in brick work or masonry.

Closer
Any portion of a brick used in constructing a wall, to close up the bond next to the end brick of a course
(See Fig-3).

Coping or Weathering
The cover applied over or the geometrical form given to a part of structure to enable it to shed rain water.

Corbel
A cantilever projecting from the face of a wall to form a bearing (see Fig-1D)



Cornice
Horizontal or ornamental feature projecting from the face of a wall (see Fig-1D)

Course
A layer of bricks including bed mortar.

Cross joint
A joint other than a bed joint normal to the wall face.

Efflorescence
A powdery incrustment of salts left by evaporation. This may be visible on the surface or may be below surface. In the latter case, this is termed as crypto Efflorescence.

Header
A brick laid with its length across the wall.

Indenting
The leaving recesses into which future work can be bonded.

Jamb
The part of the wall at the side of an opening.

Joint
A junction of bricks.

Jointing
The operation of finishing joints as the masonry work proceeds.

Pier
A thickened section forming integral part of the wall placed at intervals along the wall primarily to increase the stiffness of the wall or to carry a vertical concentrated load. The thickness of a pier is the over all thickness including the thickness of the wall, or when bonded into one leaf of a cavity wall the thickness obtained by treating this leaf as an independent wall (see Fig- (1A, 1B)).

Pillar
Pillar means a detached masonry support. This can be rectangular, circular, elliptical etc. In case of rectangular pillar, the breadth shall not exceed three times the thickness and thickness itself shall not exceed more than thrice the length of brick (See Fig-1C).

Quoin
An external corner in brick work, the term may also denote the brick used to form the quoin.

Scaffolding
A temporary erection of timber or steel work used in the construction, alteration, demolition or repairs of a building to support or to attend of the hoisting or lowering of workmen, their tools and
materials. Scaffoldings are of two types, namely single and double scaffoldings. Single scaffolding consists of a row of verticals connected to wall by horizontal supported on and tied to the structure.
Double scaffolding consists of two rows of verticals secured or leashed together with horizontal and diagonal bracings forming essentially a structure independent of the building. It may also connect to the structure at convenient points for the sake of better stability.

Sill
A brick work forming the lower boundary of door or window opening (see Fig-1D).

Spandrel
The space between the haunches and the road decking of an arch.

Strecher
A brick laid with its length in the direction of the wall.

String course
A horizontal course projecting from a wall usually introduced at every floor level or windows or below parapet for imparting architectural appearance to the structure and also keeping off the rain water. (see Fig-1D).

Templet
A pattern of sheet metal used as a guide for setting out specific section and shape.

Toothing
Bricks left projecting in alternate courses to bond with future work.

Wall joint
A joint parallel to the wall face.

A-  BRICKS/BRICK TILES/BRICK BATS/MECHANIZED AUTOCLAVE FLY ASH LIME BRICK
Bricks used in the masonry may be of the following type.

(a) Common Burnt Clay Bricks
The Common Burnt Clay Bricks shall conform to IS:1077 and shall be hand moulded or machine moulded. They shall be free from nodules of free lime, visible cracks, flaws warpage and organic matter, have a frog 100 mm in length 40 mm in width and 10 mm to 20 mm deep on one of its flat sides. Bricks made by extrusion process and brick tiles may not be provided with frogs. Each brick shall be marked (in the frog where provided) with the manufacturer’s identification mark or initials.

(b) Fly Ash Lime Bricks (FLAG bricks) 
Fly Ash Lime Bricks (FALG Bricks) : The Fly Ash Lime Bricks (FALG Bricks) shall conform to IS 12894. Visually the bricks shall be sound, compact and uniform in shape free from visible cracks, warpage, flaws and organic matter. The bricks shall be solid and with or without frog on one of its flat side.
Fly Ash: Fly ash shall conform to IS 3812.
Note: This item will be operated only for load bearing structure upto 2 storeys and for non￾load bearing walls 23 cms thick for multi-storeyed building’s. Bottom ash used as replacement of sand shall not have more than 12% loss on ignition when tested.
Sand: Deleterious materials, such as clay and silt in the sand shall preferably be less than 5%.
Lime: Lime shall conform to class ‘C’ hydrated lime of IS 712.
Additives: Any suitable additive considered not detrimental to the durability of bricks may be used.
(c) Clay Fly Ash Bricks: The clay fly ash bricks shall conform to IS 13757. The bricks shall be sound, compact and uniform in shape and colour. Bricks shall have smooth rectangular faces with sharp and square corners. The bricks shall be free from visible cracks, flaws, warpage, nodules of free lime and organic matter, the bricks shall be hand or machine moulded. The bricks shall have frog of 100 mm in length 40 mm width and 10 to 20 mm deep on one of its flat sides. If made by extrusion process may not be provided with frogs.
Fly Ash shall conform to grade I or grade II of IS 3812.
(d) Calcium Silicate Bricks: The bricks shall conform to IS 4139. The Calcium silicate bricks shall be sound, compact and uniform in shape. Bricks shall be free from visible cracks,warpage, organic matter, large pebbles and nodules of free lime. Bricks shall be solid and with or without frog. The bricks shall be made of finely grounded sand siliceous rock and lime. In addition limited quantity of fly ash conforming to IS 3812 may be used in the mix.
These bricks are also known as Fly Ash Sand Lime bricks in the construction industry.
(e) Tile Brick: The bricks of 4 cm height shall be moulded without frogs. Where modular tiles are not freely available in the market, the tile bricks of F.P.S. thickness 44 mm (1-3/4") shall be used unless otherwise specified.
(f) Brick Bats: Brick bats shall be obtained from well burnt bricks.
(g) Mechanized Autoclave Fly Ash Lime Brick: These bricks shall be machine moulded and prepared in plant by appropriate proportion of fly ash and lime. The autoclave fly ash bricks shall conform to IS 12894. Visually, the bricks shall be sound, compact and uniform shape, free from visible cracks, warpage and organic matters. The brick shall be solid with or without frog, and of 100/80 mm in length, 40 mm width and 10 to 20 mm deep one of its flat side as per IS 12894. The brick shall have smooth rectangular faces with sharp corners and shall be uniform in shape and colour. Fly ash shall conform to IS 3812 and lime shall conform to class ‘C’ hydrated lime of IS 712.

Dimensions
The brick may be modular or non-modular. Sizes for both types of bricks/tiles shall be as per Table - 1. While use of modular bricks/tiles is recommended, non-modular (FPS) bricks/tiles can also be used where so specified. Non-modular bricks/tiles of sizes other than the sizes mentioned in
Table -1 may also be used where specified.
                                                                                                                         Table -1

Classification
Bricks/Brick tiles shall be classified on the basis of their minimum compressive strength as given below
                                                                                                                         Table -2

The bricks shall have smooth rectangular faces with sharp corner and shall be uniform in colour and emit clear ringing sound when struck.
(Note: Upper limits specified in Table-2 are for calculating the average compressive strength)

Sampling and Tests
Samples of bricks shall be subjected to the following tests :
(a) Dimensional tolerance.
(b) Water absorption.
(c) Efflorescence.
(d) Compressive strength.

Sampling: For carrying out compressive strength, water absorption, efflorescence and dimensional tests, the samples of bricks shall be taken at random according to the size of lot as given in Table -3 below.
The sample thus taken shall be stored in a dry place until tests are made. For the purpose of sampling, the following definition shall apply.
(a) Lot: A collection of bricks of same class and size, manufactured under relatively similar conditions of production. For the purpose of sampling a lot shall contain a maximum, of 50,000 bricks.
In case a consignment has bricks more than 50,000 of the same classification and size and manufactured under relatively similar conditions of production, it shall be divided into lots of 50,000 bricks or part thereof.
(b) Sample: A collection of bricks selected for inspection and/or testing from a lot to reach the decision regarding the acceptance or rejection of the lot.
(c) Defective: A brick failing to meet one or more of the specified requirements.

 The samples shall be taken as below:
(i) Sampling from a Stack: When it is necessary to take a sample from a stack, the stack shall be divided into a number of real or imaginary sections and the required number of bricks drawn from each section. For this purpose bricks in the upper layers of the stack shall be removed to enable
units to be sampled from places within the stack.
Note: For other methods of sampling i.e. sampling in motion and sampling from lorries or trucks, IS :5454 may be referred.
Scale of sampling and criteria for conformity for visual and dimensional characteristics:—
Visual characteristics: The bricks shall be selected and inspected for ascertaining their conformity to the requirements of the relevant specification.
The number of bricks to be selected from a lot shall depend on the size of lot and shall be in accordance of Col. 1 and 2 of Table-3 for visual characteristics in all cases and dimensional characteristics if specified for individual bricks.
(ii) Visual Characteristics: All the bricks selected above in accordance with Col. 1 and 2 of Table -3 shall be examined for visual characteristics. If the number of defective bricks found in the sample is
less than or equal to the corresponding number as specified in Col. 3 of Table-3 the lot shall beconsidered as satisfying the requirements of visual characteristics, otherwise the lot shall be deemed as not having met the visual requirements.
(iii) Dimensional Characteristics: The number of bricks to be selected for inspecting thedimensions and tolerance shall be in accordance with Col. 1 and 4 of Table -3. These bricks will be divided into groups of 20 bricks at random and each of the group of 20 bricks thus formed will be tested for all the dimensions and tolerances. A lot shall be considered having found meeting the requirements of dimensions and tolerance if none of the groups of bricks inspected fails to meet the specified requirements.
                                                                                                                            Table -3

Note: In case the lot contains 2000 or less bricks the sampling shall be as per decision of the Engineer-in-Charge.
(iv) Scale of Sampling and Criteria for Physical Characteristics: The lot which has been found satisfactory in respect of visual and dimensional requirements shall be next tested for physical characteristics like compressive strength, water absorption, efflorescence as specified in relevant material specification. The bricks for this purpose shall be taken at random from those already selected above. The number of bricks to be selected for each of these characteristics shall be in accordance with relevant columns of Table -4.
                                                                                                                          Table -4

Note: In case the lot contains 2000 or less bricks, the sampling shall be as per decision of Engineer-in-Charge.

(v) A lot shall be considered having satisfied the requirements of physical characteristics if the condition stipulated here in are all satisfied.
(a) From the test results for compressive strength, the average shall be calculated and shall satisfy the requirements specified in relevant material specification.
Note: In case any of the test results for compressive strength exceeds the upper limit for the class of bricks, the same shall be limited to the upper limit of the class for the purpose of averaging.
(b) Wherever specified in the material specification, the compressive strength of any individual bricks tested in the sample shall not fall below the minimum average compressive strength specified for the corresponding class of brick by more than 20 percent.
(c) From the test results for water absorption, the average for the bricks in the sample shall be calculated and shall satisfy the relevant requirements specification in material specification.
(d) The number of bricks failing to satisfy the requirements of the efflorescence specified in the
relevant specification should not be more than the permissible no. of defectives given in Col.3 of Table -4.

Dimensional Tolerances: The dimensions of modular bricks when tested as described above shall be within the following limits per 20 bricks or locally available size as approved by Engineer-in-charge.
(a) For modular size
Length 7320 to 3880 mm (3800 ± 80 mm)
Width 1760 to 1840 mm (1800 ± 40 mm)
Height 1760 to 1840 mm (1800 ± 40 mm) for 90 mm high bricks
760 to 840 mm (800 ± 40 mm) for 40 mm high bricks
(b) For non modular bricks
Length 4520 to 4680 mm (4600 ± 80 mm)
Width 2240 to 2160 mm (2200 ± 40 cm)
Height 1440 to 1360 mm (1400 ± 40 mm) for 70 mm high bricks
640 to 560 mm (600 ± 40 mm) for 30 mm high bricks


Brick Tiles


760 to 840 mm (800 ± 40 mm) for 40 mm high brick tiles
In case of non-modular bricks, % age tolerance will be ± 2% for group of 20 numbers of class 10 bricks,
and ± 4% for other class of bricks.

Compressive Strength: The bricks, when tested shall have a minimum average compressive strength for various classes as given in Table -2. The compressive strength of any individual brick tested shall not fall below the min. average compressive strength specified for the corresponding class of brick by more than 20%. In case compressive strength of any individual brick tested exceeds the upper limit specified in Table -2 for the corresponding
class of bricks, the same shall be limited to upper limit of the class as specified in Table -2 for the purpose of calculating the average compressive strength.

Water Absorption: The average water absorption of bricks when tested shall be not more than 20% by weight.

Efflorescence: The rating of efflorescence of bricks when tested shall be not more than moderate.




# The rating to efflorescence in ascending order shall be reported as ‘NIL’, ‘SLIGHT’, ‘MODERATE’, 
‘HEAVY’ or ‘SERIOUS’ in accordance with the following :
(a) NIL: When there is no perceptible deposit of efflorescence.
(b) SLIGHT: When not more than 10 per cent of the area of the brick is covered with a thin deposit of
salts.
(c) MODERATE: When there is heavier deposit and covering upto 50% of the area of the brick surface 
but unaccompanied by powdering or flaking of the surface.
(d) HEAVY: When there is a heavy deposit of salts covering 50% or more of the brick surface but unaccompanied by powdering or flaking of the surface.
(e) SERIOUS: When there is heavy deposit of salts, accompanied powdering and/or flaking of the surface and tending to increase in the repeated wetting of the specimen.

Sewer Bricks
Sewer bricks are intended for the lining of walls, roofs and floors of sewers used for ordinary sanitary (domestic) sewage. The general practice in the country is also to utilize common building bricks in the construction of sewers which is not satisfactory. However, these sewer bricks may not be suitable for sewers dealing with industrial effluent (sewage) for which the use of acid resistant bricks in accordance with IS 4860 may be considered. Sewer bricks shall conform to IS 4885.

Dimensions and Tolerances
Dimensions: The standard sizes of the sewer bricks shall be as follows:


For sewers of special shapes, such as the oval sewers, the bricks may have to  be suitable tapered to conform to the radii of curvature of the arches and barrels and sides of sewers.

Tolerance: The permissible tolerance on the dimensions specified above shall be as follows :



Compressive Strength:The average compressive strength obtained on a sample of sewer bricks when tested in accordance with the procedure laid down in IS 3495 (Part I) shall be not less than 17. 5 N/mm2 (175 kgf/cm2 approximately) and the individual strength of any brick shall be not less than 16 N/mm2 (160 kgf/cm2 approximately).

Water Absorption: The average value of water absorption for five bricks after 24 h cold waterimmersion test when tested in accordance with IS 3495 (Part 2) shall not exceed 10 per cent of the average dry weight of the brick and the absorption for any individual brick shall not exceed 12 per cent.

Efflorescence: When the bricks are tested in accordance with the method laid down in IS 3495(Part 3), the rating of efflorescence shall not be more than ‘slight’.

Burnt Clay Perforated Building Bricks

General Quality: The bricks shall be made of suitable clay and shall be thoroughly burnt at the maturing temperature of clay. They shall be free from cracks, flaws and nodules of free lime. They shall have rectangular face with sharp straight edge at right angle. They shall be of uniform colour and texture. These bricks generally should conform to IS 2222.

 Dimensions and Tolerances: The standard size of burnt clay perforated bricks shall be as follows:


The permissible tolerances on the dimensions shall be as follows:


Note: The tolerances specified above shall apply to measurements on individual bricks.

Perforations:The area of perforation shall be between 30% and 45% of the total area of thecorresponding face of the bricks.

The perforation shall be uniformly distributed over the surface. In the case of rectangular perforations, the larger dimension shall be parallel to the longer side of the brick. The shorter side of the perforation shall be less than 20 mm incase of rectangular perforations and less than 25 mm diameter in case of circular perforations.

The area of each perforation shall not exceed 500 square mm.

The thickness of any shell shall not be less then 15 mm and that of any web not less than 10 mm.

Compressive Strength: The bricks when tested in accordance with the procedure laid down inIS 3495 (Parts 1 to 4) shall have a minimum average compressive strength of 7 N/ mm2 on net area.

The compressive strength of any individual brick tested shall not fall below the minimum compressive strength specified for the corresponding class of bricks. The lot shall then be checked for next lower class of brick.

Water Absorption: The bricks when tested in accordance with the procedure laid down in IS 3495 (parts 1 to 4): after immersion in cold water for 24 hours water absorption shall not be more than 20 percent by weight.

Efflorescence: The bricks when tested in accordance with the procedure laid down in IS 3495 (Parts 1 to 4) shall have a rating of efflorescence not more than ‘slight’.

Warpage: The bricks when tested in accordance with the procedure laid down in IS 3495 (parts 1 to 4) the average warpage shall not exceed 3%



B- BRICK WORK


Classification
The brick work shall be classified according to the class designation of bricks used.

Mortar
The mortar for the brick work shall be as specified, and conform to accepted standards. Lime shall not be used where reinforcement is provided in brick work.

Soaking of Bricks
Bricks shall be soaked in water before use for a period for the water to just penetrate the whole depth of the bricks. Alternatively bricks may be adequately soaked in stacks by profusely spraying with clean water at regular intervals for a period not less than six hours. The bricks required for masonry work using mud mortar shall not be soaked. When the bricks are soaked they shall be removed from the tank sufficiently early so that at the time of laying they are skin-dry. Such soaked bricks shall be stacked on a clean place where they are not again spoiled by dirt earth etc.

Note I: The period of soaking may be easily found at site by a field test in which the bricks are soaked in water for different periods and then broken to find the extent of water penetration. The least period that corresponds to complete soaking will be the one to be allowed for in construction work.

Note II : If the bricks are soaked for the required time in water that is frequently changed the soluble salt in the bricks will be leached out, and subsequently efflorescence will be reduced.

Laying

Bricks shall be laid in English Bond (Fig-2, Fig-3, Fig-4) unless otherwise specified. For brick work in half brick wall, bricks shall be laid in stretcher bond. Half or cut bricks shall not be used except as closer where
necessary to complete the bond. Closers in such cases, shall be cut to the required size and used near the ends of the wall. Header bond shall be used preferably in all courses in curved plan for ensuring better alignment.







Note: Header bond shall also be used in foundation footings unless thickness of walls (width of footing) makes the use of headers impracticable. Where thickness of footing is uniform for a number of courses, the top course of footing shall be headers.

All loose materials, dirt and set lumps of mortar which may be lying over the surface on which brick works to be freshly started, shall be removed with a wire brush and surface wetted. Bricks shall be laid on a full bed of mortar, when laying, each brick shall, be properly bedded and set in position by gently pressing with the handle of a trowel. Its inside face shall be buttered with mortar before the next brick is laid and pressed against it. Joints shall be fully filled and packed with mortar such that no hollow space are left inside the joints.

The walls shall be taken up truly in plumb or true to the required batter where specified. All courses shall be laid truly horizontal and all vertical joints shall be truly vertical. Vertical joints in the alternate course shall come directly one over the other. Quoin, Jambs and other angles shall be pro-perly plumbed as the work proceeds. Care shall be taken to keep the perpends properly aligned within following maximum permissible tolerances :

(a) Deviation from vertical within a storey shall not exceed 6 mm per 3 m height.

(b) Deviation in verticality in total height of any wall of building more than one storey in height shall not exceed 12.5 mm.

(c) Deviation from position shown on plan of any brick work shall not exceed 12.5 mm.

(d) Relative displacement between load bearing wall in adjacent storeys intended to be vertical alignments shall not exceed 6 mm.
(e) A set of tools comprising of wooden straight edge, masonic spirit levels, square, 1 metre rule line and plumb shall be kept on the site of work for every 3 masons for proper check during the progress of work.

All quoins shall be accurately constructed and the height of brick courses shall be kept uniform. This will be checked using graduated wooden straight edge or storey rod indicating height of each course including thickness of joints. The position of damp proof course, window sills, bottom of lintels, top of the wall etc. along the height of the wall shall be marked on the graduated straight edge or storey rod. Acute and obtuse quoins shall be bonded, where practicable in the same way as square quoins. Obtuse quoins shall be formed with squint showing three quarters brick on one face and quarter brick on the other.


The brick work shall be built in uniform layers.
No part of the wall during its construction shall rise more than one metre above the general construction level. Parts of wall left at different levels shall be raked back at an angle of 45 degrees or less with the horizontal. Toothing shall not be permitted as an alternative to raking back. For half brick partition to be keyed into main walls, indents shall be left in the main walls.

All pipe fittings and specials, spouts, hold fasts and other fixtures which are required to be built into the walls shall be embedded, as specified, in their correct position as the work proceeds unless otherwise directed by the Engineer-in-Charge.

Top courses of all plinths, parapets, steps and top of walls below floor and roof slabs shall be laid with brick on edge, unless specified otherwise. Brick on edge laid in the top courses at corner of walls shall be properly radiated and keyed into position to form cut (maru) corners as shown in Fig-4. Where bricks cannot be cut to the required shape to form cut (maru) corners, cement concrete 1:2:4 (1 cement : 2 coarse sand : 4 graded stone aggregate 20 mm nominal size) equal to thickness of course shall be provided in lieu of cut bricks.

Bricks shall be laid with frog (where provided) up. However, when top course is exposed, bricks shall be laid with frog down. For the bricks to be laid with frog down, the frog shall be filled with mortar before placing the brick in position.

In case of walls one brick thick and under, one face shall be kept even and in proper plane, while the other face may be slightly rough. In case of walls more than one brick thick, both the faces shall be kept even
and in proper plane.

To facilitate taking service lines later without excessive cutting of completed work, sleeves (to bepaid separately) shall be provided, where specified, while raising the brick work. Such sleeves in external walls shall be sloped down outward so as to avoid passage of water inside.

Top of the brickwork in coping and sills in external walls shall be slightly tilted. Where brick coping and sills are projecting beyond the face of the wall, drip course/throating (to be paid separately) shall be provided where indicated.

Care shall be taken during construction that edges of jambs, sills and projections are not damaged in case of rain. New built work shall be covered with gunny bags or tarpoulin so as to prevent the mortar from
being washed away. Damage, if any, shall be made good to the satisfaction of the Engineer-in-Charge.

Vertical reinforcement in the form of bars (MS or high strength deformed bars or thermo-mechanically treated bars as per direction of Engineer-in- Charge)), considered necessary at the corners and junction of walls and jamb opening doors, windows etc. shall be encased with cement mortar not leaner than 1:4 (1 cement : 4 coarse sand), or cement concrete mix as specified. The reinforcement shall be suitably tied, properly embedded in the foundation and at roof level. The dia. of bars shall not be less than 8 mm and concrete grade shall be minimum 1:3:6 (1 cement : 3 coarse sand : 6 graded stone aggregate 20 mm nominal size).

In retaining walls and the like, where water is likely to accumulate, weep holes, 50 to 75 mm square shall be provided at 2 m vertically and horizontally unless otherwise specified. The lowest weep hole shall be
at about 30 cm above the ground level. All weep holes shall be surrounded by loose stones and shall have sufficient fall to drain out the water quickly.

Note : Work of providing loose stone will be payable extra.

Work of cutting chases, wherever required to be made in the walls for housing G.I. pipe, CI pipe or any other fixtures shall be carried out in various locations as per guidelines given below :

(a) Cutting of chases in one brick thick and above load bearing walls.

(i) As far as possible services should be planned with the help of vertical chases. Horizontal chases should be avoided.
(ii) The depths of vertical chases and horizontal chases shall not exceed one-third and one-sixth of the thickness of the masonry respectively.
(iii) When narrow stretches of masonry (or short length of walls) such as between doors and windows, cannot be avoided they should not be pierced with openings for soil pipes or waste pipes or timber joints, etc. Where there is a possibility of load concentration such narrow lengths of walls shall be checked for stresses and high strength bricks in mortar or concrete
walls provided, if required.
(iv) Horizontal chases when unavoidable should be located in the upper or lower one-third of height of storey and not more than three chases should be permitted in any stretch of a wall.

No continuous horizontal chase shall exceed one metre in length. Where unavoidable, stresses in the affected area should be checked and kept within the permissible limits.

(v) Vertical chases should not be closer than 2 m in any stretch of a wall. These shall be kept away from bearings of beams and lintels. If unavoidable, stresses in the affected area should be checked and kept within permissible limits.
(vi) Masonry directly above a recess, if wider than 30 cm horizontal dimension) should be supported on lintel. Holes in masonry may be provided upto 30 cm width and 30 cm height without any lintel. In the case of circular holes in the masonry, no lintel need be provided for holes upto 40
cm in diameter.

(b) Cutting of chases in half brick load bearing walls.
No chase shall be permitted in half brick load bearing walls and as such no reccessed conduits and concealed pipes shall be provided with half brick thick load bearing walls.
(c) Cutting of chases in half brick non-load bearing wall :
Services should be planned with the help of vertical chases. Horizontal chase should be provided only when unavoidable.


 Joints

The thickness of all types of joints including brick wall joints and cross joints shall be such that four course and three joints taken consecutively shall measure as follows:
(i) In case of modular bricks conforming to IS 1077 specification for common burnt clay buildings bricks, equal to 39 cm.

(ii) In case of non-modular bricks, it shall be equal to 31 cm.

Note : Specified thickness of joints shall be of 1 cm. Deviation from the specified thickness of all joints shall not exceed one-fifth of specified thickness.

Finishing of Joints: The face of brick work may be finished flush or by pointing. In flush finishing either the face joints of the mortar shall be worked out while still green to give a finished surface flush with the
face of the brick work or the joints shall be squarely raked out to a depth of 1 cm while the mortar is still green for subsequently plastering. The faces of brick work shall be cleaned with wire brush so as to remove any splashes of mortar during the course of raising the brick work. In pointing, the joints shall be squarely raked out to a depth of 1.5 cm while the mortar is still green and raked joints shall be brushed to remove dust and loose particles and well wetted, and shall be later refilled with mortar to give ruled finish. Some such finishes
are ‘flush’, ‘weathered’, ruled, etc.

Curing
The brick work shall be constantly kept moist on all faces for a minimum period of seven days. Brick work done during the day shall be suitably marked indicating the date on which the work is done so as to keep a
watch on the curing period.

Scaffolding
Scaffolding shall be strong to withstand all dead, live and impact loads which are likely to come on them.
Scaffolding shall be provided to allow easy approach to every part of the work.

(A) Single Scaffolding: Where plastering, pointing or any other finishing has been indicated for brick work, single scaffolding may be provided, unless otherwise specified. In single scaffolding, one end of the put￾logs/pole shall rest in the hole provided in the header course of brick masonry. Not more than one header for
each put-log/pole shall be left out. Such holes shall not be allowed in the case of pillars, brick work less than one metre in length between the openings or near the skew backs of arches or immediately under or near the structural member supported by the walls. The holes for putlogs/poles shall be made good with brick work and
wall finishing as specified.
(B)  Double Scaffolding: Where the brick work or tile work is to be exposed and not to be finished with plastering etc. double scaffolding having two independent supports, clear of the work, shall be provided.

Measurements
Brick work shall be measured in cubic metres unless otherwise specified. Any extra work over the specified dimensions shall be ignored. Dimensions shall be measured correct to the nearest 0.01 m i.e. 1 cm.  Areas shall be calculated to the nearest 0.01 sq mtrs and the cubic contents shall be worked out to the nearest 0.01 cubic metres.

Brick work shall be measured separately in the following stages:
(a) From foundation to floor one level (Plinth level)
(b) Plinth (floor one) level to floor two level
(c) Between two specified floor levels above floor two level

Note : (i) Brick work in parapet walls, mumty, lift machine room and water tanks constructed on the roof upto 1.2 m height above roof shall be measured together with the corresponding work of the floor next below.

No deductions or additions shall be done and no extra payment made for the following :

Note : Where minimum area is defined for deduction of an opening, void or both, such areas shall refer only to opening or void within the space measured.
(a) Ends of dissimilar materials (that is, joists, beams, lintels, posts, girders, rafters, purlins, trusses, corbels, steps, etc.); up to 0.1 m2 in section;
(b) Opening up to 0.1 m2 in area (see Note);
(c) Wall plates, bed plates, and bearing of slabs, chajjas and the like, where thickness does not exceed 10 cm and bearing does not extend over the full thickness of wall;
(d) Cement concrete blocks as for hold fasts and holding down bolts;
(e) Iron fixtures, such as wall ties, pipes upto 300 mm diameter and hold fasts for doors and windows; and
(f) Chases of section not exceeding 50 cm in girth.
(g) Bearing portion of drip course, bearing of moulding and cornice.

Note : In calculating area of an opening, any separate lintel or sills shall be included with the size of the opening but end portions of lintel shall be excluded. Extra width of rebated reveals, if any, shall also be excluded.

 Walls half brick thick and less shall each be measured separately in square metres stating thickness.

Walls beyond half brick thickness shall be measured in multiples of half brick which shall be deemed to be inclusive of mortar joints. For the sizes of bricks specified in Table -1, half brick thickness shall mean 100
mm for modular and 115 mm for non-modular bricks.
Where fractions of half brick occur due to architectural or other reasons, measurement shall be as follows :
(a) upto 1/4th brick-actual measurements and
(b) exceeding 1/4 brick-full half bricks.

String courses, projecting pilasters, aprons, sills and other projections shall be fully described and measured separately in running metres stating dimensions of each projection.

Square or rectangular pillars shall be measured separately in cubic metres in multiple of half brick.

Circular pillars shall be measured separately in cubic metres as per actual dimensions.

Brick work curved on plan shall be measured like the brick work in straight walls and shall include all cutting and wastage of bricks, tapered vertical joints and use of extra mortar, if any. Brick work curved on plan to a mean radius not exceeding six metres shall be measured separately and extra shall be payable over the rates for brick work in straight walls. Nothing extra shall be payable if the mean radius of the brick work curved in plan exceeds six metres.

Tapered walls shall be measured net as walls and extra payment shall be allowed for makingtapered surface for brick work in walls.

Brick work with brick tiles shall be measured and paid for separately.

Rate

The rate shall include the cost of materials and labour required for all the operations described above except the vertical reinforcement and its encasement in cement mortar or cement concrete. The rate shall also include the following :
(a) Raking out joints or finishing joints flush as the work proceeds;
(b) Preparing tops of existing walls and the like for raising further new brick work.
(c) Rough cutting and waste for forming gables, splays at eaves and the like.
(d) Leaving holes for pipes upto 150 mm dia. and encasing hold fasts etc.
(e) Rough cutting and waste for brick work curved in plan and for backing to stone or other types of facing.
(f) Embedding in ends of beams, joists, slabs, lintels, sills, trusses etc.
(g) Bedding wall plates, lintels, sills, roof tiles, corrugated sheets, etc. in or on walls if not covered in respective items and
(h) Leaving chases of section not exceeding 50 cm in girth or 350 sq cm in cross-section.
(i) Brick on edge courses, cut brick corners, splays reveals, cavity walls, brick works curved on plan to a mean radius exceeding six metres.


C- BRICK WORK IN ARCHES


The detailed specifications for brick work as discussed above ( B- BRICK WORK )shall apply, in so far as these are applicable.
Arch work shall include masonry for both gauged as well as plain arches. In gauged arches, cut or moulded bricks shall be used. In plain arches, uncut bricks shall be used.
Brick forming skew-backs shall be dressed or cut so as to give proper radial bearing to the end voussiors.
Defects in dressing of bricks shall not be covered by extravagant use of mortar, nor shall the use of chips or bats etc. be permitted.
The bricks of the spandrel wall at their junctions with the extrudes of the arch shall be cut to fit the curvature of the arch.



Circular Arches

These shall be either
(a) plain arches, and shall be built in half brick concentric rings with break joints, or
(b) gauged arches built with bricks cut or moulded to proper shape. The arch work shall be carried up from both ends simultaneously and keyed in the centre. The bricks shall be flush with mortar and well pressed into their positions so as to squeeze out a part of their mortar and leave the joints thin and compact. All joints shall
be full of mortar and thickness of joints shall not be less than 5 mm nor more than 15 mm.
After the arch is completed, the haunches shall be loaded by filling up the spandrels upto the crown level of the arch. Care shall be taken to load the haunches on two sides of the spandrels.
When the arch face is to be pointed (and not plastered), the face bricks shall be cut to proper shape or moulded, so as to have the joints not more than 5 mm thick. These shall be laid with radial joints to the full depth of the arch. The voussoirs shall break joints to the full depth of the arch.

Flat Arches
These shall be gauged arches of brick cut or moulded to proper shape. The extrados shall be kept horizontal and the intrados shall be given slight camber of 1 in 100 of the span. The centre of the arch from which joints shall radiate, shall be determined by the point of the inter-section of the two lines drawn from the ends of the arch at the springing level and at 60° to horizontal.

In flat arches, bricks shall be laid with radial joints to the full depth of arch and voussoirs breaking joints with each other. The arch work shall be carried up from both ends simultaneously and keyed in the centre. The thickness of the joints shall not exceed 5 mm. Flat arches may be used for the sake of appearance but for purpose
of carrying loads of the wall above, these shall be used in conjunction with relieving arches, lintels placed below.

Centring and Shuttering
The centring and shuttering for the arch shall be got approved by the Engineer-in- Charge before the arch work is started. It shall be strong enough to bear the dead load of the arch and the live loads that are likely to come upon it during construction, without any appreciable deflections.
The shuttering shall be tightened with hard wood wedged or sand boxes, so that the same could be eased without jerks being transmitted to the arch. The sequence of easing the shuttering shall be got approved from the Engineer- in-Charge. The shuttering shall be struck within 48 hours of the completion of the arch but not before 24 hours. This shall be done after the spandrel has been filled in and the arch loaded.

Measurements
The length of the arch shall be measured as the mean of the extrados and intrados of the arch correct to a cm. The thickness of the arch shall be measured in multiples of the half brick.
The breadth in the direction of the thickness of wall shall be measured as specified.
The cubical contents shall be calculated in cubic metre, correct to two places of decimal.
For arches exceeding 6 m in spans extra payment shall be made on the actual area of the soffit for additional cost of centring including all strutting, bolting, wedging, easing, striking and its removal.

Rate
The rate is inclusive of the cost of the materials and labour required for all the operations described above.

D - HALF BRICK WORK

Brick work in half brick walls shall be done in the same manner as described above ( B - BRICK WOK, Laying )except that the bricks shall be laid in stretcher bond. When the half brick work is to be reinforced, 2 Nos. M.S. bars of 6 mm dia., shall be embedded in every third course as given in the item (the dia of bars shall not exceed 8 mm).
These shall be securely anchored at their end where the partitions end. The free ends of the reinforcement shall be keyed into the mortar of the main brick work to which the half brick work is joined. The mortar used
for reinforced brick work shall be rich dense cement mortar of mix 1:4 (1 cement: 4 coarse sand). Lime mortar shall not be used. Over laps in reinforcement, if any shall not be less than 30 cm.
The mortar interposed between the reinforcement bars and the brick shall not be less than 5 mm.
The mortar covering in the direction of joints shall not be less than 15 mm.

Measurements
The length and height of the wall shall be measured correct to a cm. The area shall be calculated in sq.m. where half brick wall is joined to the main walls of one brick or greater thickness and measurements for half brick wall shall be taken for its clear length from the face of the thicker wall.

Rate
The rate includes the cost of the materials and labour involved in all the operations described above except reinforcement which is to be paid for separately.

E - BRICK TILE WORK

The work shall be done in the same manner as described in (B - BRICK WOK, Laying) except that brick tile shall be used instead of bricks. The measurement and rate shall be same as specified under (B - BRICK WOK).

F - HONEY COMB BRICK WORK

The honeycomb brick work shall be done with specified class of brick, laid in specified mortar. All joints and edges shall be struck flush to give an even surface.
The thickness of the brick honeycomb work shall be half-brick only, unless otherwise specified.
Openings shall be equal and alternate with half brick laid with a bearing of 2 cm on either side.
Measurements
The length and height shall be measured correct to a cm. Area shall be calculated in square metres correct to two places of decimal. Honeycomb openings shall not be deducted.

Rate
The rate includes the cost of materials and labour involved in all the operations described above.

G - JOINING OLD BRICK WORK WITH NEW BRICK WORK

In case the height of the bricks of old as well as new work is same, the old work shall be toothed to the full width of the new wall and to the depth of a quarter of brick in alternate courses. In case the height of the bricks is unequal, then the height of each course of new work shall be made equal to the height of the old work by adjusting thickness of horizontal mortar joints in the new wall. Where necessary, adjustment shall be made equal to thickness of old wall by adjusting the thickness of vertical joints.

For joining new cross wall to old main walls, a number of rectangular recesses of width equal to the thickness of cross wall, three courses in height and half a brick in depth shall be cut in the main walls. A space of the three courses shall be left between two consecutive recesses. The new cross wall shall be bonded into the recesses to avoid any settlement.

Joining of old brick work with the new brick work shall be done in such a way that there shall not be any hump or projection at the joint.

Measurement
The height and thickness of vertical face in contact with new work shall be measured to the nearest 0.01 m and the area shall be calculated to the nearest 0.01 sqm.

Rate
The rate includes the cost of labour and material involved in all the operations described above.

H - MOULDING AND CORNICES

The specifications described under(B - BRICK WOK) shall apply in so far these are applicable. Mouldings and cornices shall be made with bricks as specified for brick work. The bricks shall be cut and dressed to the required shape as shown in the architectural drawings.

Cornices shall not ordinarily project by more than 15 cm to 20 cm and this projection shall be obtained by projecting each brick course by more than one fourth of the length. For cornices projecting more than 20 cm and requiring more than quarter bricks projection, metal cramps shall be used and paid for separately.

Corbelling shall be brought roughly to shape by plastering with the specified mortar. When the mortar is still green, the mouldings shall be finished straight and true with the help of metal templates.

Curing and Protection
The mouldings and cornices shall be cured for at least seven days. These shall be protected from the effects of sun and rain by suitable covering and also from damage during the execution of the work.

Measurements
For the purpose of measurements, the sectional periphery of mouldings and cornices (excluding the portion in contact with wall) shall be measured in centimetres and length in metres (fig. below) .
The girth and length shall be measured correct to a cm. No deduction shall be made from the masonry of wall for the bearing of the moulding and cornices.


Note : 1 The sectional periphery curve ABCDEF.
2. Length FA shall not be measured.

Rate
The rate includes the cost of materials and labour involved in all the operations described above.

I- BRICK WORK UNDER WATER OR FOUL CONDITIONS

Brick Work under following conditions :
(i) Work in or under water/or liquid mud;
(ii) Work in or under foul positions

Shall be measured separately for payment of extra rate over and above the quantity measured and paid under (B - BRICK WOK, Measurements)


J- EXPOSED BRICK WORK

Facing Bricks
The facing bricks made from suitable soils shall be free from cracks, flaws, nodules of free lime warpage and organic matter. These shall be thoroughly burnt and shall have plane rectangular faces with parallel sides and sharp straight right angled edges. Facing bricks shall have uniform colour and even texture. Unless otherwise specified, facing bricks shall be machine moulded only. As far as possible, total requirement of facing bricks for a work shall be arranged from the same kiln. Bricks with chipped edges and broken corners shall not be used.

Dimensions and Tolerances
The standard sizes of machine moulded facing bricks shall be as specified in 6.1.1.
(A-BRICKS/BRICK TILES/BRICK BATS/MECHANIZED AUTOCLAVE FLY ASH LIME BRICK, Dimensions)

The permissible tolerances shall be as under:

Note: Tolerance and Dimensions for selected hand moulded bricks + 4 mm in length and + 3 mm in width
and thickness).

Sampling

As per Para (A-BRICKS/BRICK TILES/BRICK BATS/MECHANIZED AUTOCLAVE FLY ASH LIME BRICK, Sampling and Tests )

 Physical Requirements

Facing bricks shall be of class designation 75 unless otherwise specified. Average compressive strength shall not be less than 7.5 N/mm2, water absorption shall not exceed 20 per cent by weight and efflorescence rating shall be nil when tested and tolerance in dimensions shall be checked as per the procedure laid down in Appendix A-2.
Mortar, Soaking of Bricks and laying shall be as specified in Para (B- BRICK WORK, Mortar,  Soaking of Bricks and laying respectively).

Joints in the exposed brick work shall be truly horizontal and vertical and kept uniform with the help of wooden or steel strips. The thickness of joints shall be as per  (B- BRICK WORK,Joints)

Curing and scaffolding shall be as specified (B- BRICK WORK,Curing, scaffolding)  respectively.

Measurements

Exposed brick work in face using machine moulded bricks and selected hand moulded bricks shall be measured separately and the measurement shall be as specified in (B- BRICK WORK,Measurements).

Rate

The rates shall be as specified in ( B- BRICK WORK,Rate) and shall also include the following :
(a) Labour for selecting bricks and wastage of bricks where use of selected hand moulded brick is specified.
(b) Leaving uniform horizontal and vertical grooves of specified depth and providing joints of required thickness using wooden or steel strips as the work proceeds.

K - CAVITY WALL

It is a wall comprising of two leaves, each leaf being built of masonry units and separated by a cavity so as to provide an air space within the wall and tied together with metal ties or bonding units to ensure that two leaves act as one structural unit. The width of the cavity shall not be less than 50 mm and not more than 115 mm. Each leaf of the cavity wall shall not be less than 75 mm. The space between the leaves being either left as cavity or filled with non-load bearing insulating and water proofing material.

Metal Ties

These may be of galvanised iron, wrought iron, gun metal, brass, copper, stainless steel or any such corrosion resistant metal, made of flats 20 x 5 mm cranked or twisted at their mid point with ends split and fish
tailed. The ties shall be built into horizontal bed joints during erection, placed sloping towards the exterior side to prevent water from flowing along it from outer to inner leaf side (For details refer Fig. 6).




Bonding Units

These shall be preferably precast R.C.C. units having cross-section as per Fig- 6.
Length of the Bonding units will be sum of thickness of both leaves plus width of cavity if the leaves are 75 mm or 115 mm. If the leaves are more than 115 mm thick, then the length of a unit will be 2 × 115 + width of cavity as shown in Fig. 6 . Precast RCC units shall be provided with 2 no., 6 mm mild steel reinforcement bars tied with 2 no. 3 mm. dia. M.S. wire/hard drawn wire cross bars (As shown in Fig. 6 ) placed in the centre of units.
Cement concrete used in the bonding units shall not be leaner than 1:3:6 (1 cement : 3 coarse sand : 6 graded stone aggregate 20 mm nominal size).

Spacing

Metal ties/bonding units shall be spaced not more than 90 cm apart horizontally and 45 cm vertically and staggered in each course. Additional ties shall be used near openings.

 Restrictions

Cavity walls shall not normally be built more than 7.5 metres in height and 9 metres in length. Where large lengths and heights are desired, the wall shall be divided into panels with strengthening measures such as pillars etc. Cavity shall be covered at the top with at least two courses of masonry unit and/or a coping over it.

Adoption of cavity walls is not recommended when heavy concentrated load from beam etc. are to be supported by walls.

Measurements and Rate

(a) Brick work in cavity walls shall be included and measured with general brick work. The width of the cavity shall not be measured. Skin of cavity wall, half brick thickness shall be measured as and paid as described in   (B- BRICK WORK,Measurements) and  (D - HALF BRICK WORK.

(b) The forming of the cavity shall be given in square metres stating the width of the cavity and shall include the metal ties/bonding unit specifying the numbers per square metre.
(c) Labour and material for closing cavities at the jambs, sills and heads of opening shall be as described and measured separately in running metres.
(d) The item shall include use of device for keeping cavity clear and forming the requisite weep and vent holes and nothing extra on this account shall be payable.

L - GYPSUM PARTITION PANELS

The material shall conform to IS:2849.

Dimensions
As per the item nomenclature.

Laying
(i) Panels are stored in a dry place and water should not come in contact with panels during or after construction. If the panels get wet, they should be dried before use.
(ii) The floor should be perfectly level before laying the first course. All panels must be properly aligned to the plumb. Successive layer of panels must be alternatively staggered so that vertical joints are not in the same line.
(iii) The recommended quantity of Gypsum Bonding Plaster must be used for joints and filling the grooves made for conduits, pipelines, etc. Excess Bonding Plaster must be scooped and removed, so that the joints and the places where the grooves are filled in are flush and even.
(iv) The walls should be dry and sanding done properly especially at joints before the primer is applied so that the surface is even and joints will not be visible after painting. Avoid chasing with chisel and hammer. Use electrical saw or grooving tools for conduiting etc.
(v) The recommended span of walls is maximum 6 meters and maximum height is 4.5 meters.
(vi) Gypsum panel can easily be cut with coarse tooth hand saw, electric jigsaw, etc. The panels can be cut, sawn, drilled, milled or dowelled on the job. For concealed piping and conduit, the depth of groove should not exceed 50 mm. Hammer and chisel techniques to form chases must be avoided.
(vii) Sanding: This application is to make the surface level without undulations. To make the gypsum wall surface level (in particular at joints, where there is excess bonding plaster), do sanding with sand paper at joints and other places, wherever you find uneven surface, otherwise joints will be visible after painting. It is important to sand all joints uniformly.
(viii) Primer Application: The purpose of the primer is to give a better adhesion to the paint and also to reduce consumption of paint on the wall. Water thinable primers shall be used only.

Measurements

The length and height shall be measured correct to a cm. Area shall be calculated in square meters correct to two place of decimal. No deduction shall be made for ducts, opening made from the standard size of panel.

Rate

The rate shall include the cost of materials and labour involved in all the operations described above.

M-AUTOCLAVED AERATED CONCRETE BLOCK MASONRY WORK

 Terminology

For the purpose of, Autoclave Aerated Concrete Block masonry work, the following definitions shall apply

1. Autoclaved -Steam curing of concrete Products, sand lime bricks, asbestos cement products, hydrous calcium silicate insulation Products, or cement in an autoclave at maximum ambient temperatures generally between 1700C to 2150C.
2. Block - A concrete masonry unit, any one of the external dimensions of which is greater than the corresponding dimension of a brick as specified in IS : 3952-1978 and of such size and mass as to permit it to be handled by one man. Furthermore, to avoid confusion with slabs and Panels, the height of the block shall not exceed either its length or six times its width.
3. Block Density - The density calculated by dividing the mass of a block by the overall volume, including holes or cavities and end recesses..
4. Drying Shrinkage - The difference between the length of specimen which has been immersed in water and then subsequently dried to constant length, all under specified conditions; expressed as
a percentage of the dry length of the specimen.
5. Gross Area-The total area occupied by a block on its loading face, including areas of the cavities and end recesses.
6. Height -The vertical dimension of the exposed face of a block, excluding any tongue or other device designed to provide mechanical keying
7. Length - The horizontal dimension of the exposed face of a block excluding any tongue or other device designed to provide mechanical keying.
8. Width -The external dimension of a block at the bedding plane, measured at right angles to the length and height of the block.

 Dimensions & Tolerances:

Autoclave Aerated Concrete Block shall be made in sizes and shapes to fit different concrete needs. They include stretcher, corner, double corner or pier, jamb, header, bull nose, partition block and concrete floor units.
Autoclave Aerated Concrete Block shall be referred to by its normal dimension the term ‘normal’ means that the dimension includes the thickness of the mortar joints. The actual dimension shall be 10mm short of the normal dimension (or 6mm short in special areas finer joints as specified).

The normal dimension of the concrete block shall be as follows:-
Length :                    400, 500 or 600 mm
Height :                    200, 250 or 300 mm
Width :                    100, 150, 200 or 250 mm

In addition, Autoclave Aerated Concrete Block shall be manufactured in half length of 200, 250 or 300 mm correspond to the full lengths.

The nominal dimensions of the units are so designed that taking account of the thickness of mortar joints, they will produce wall length sand heights which will conform to the principles of modular
co-ordination.

Block of sizes other than those specified above, may also be used if so specified in the case of special Autoclave Aerated Concrete Block such as jallie or screen wall and ornamental block ,the specified size may not necessarily apply.

The maximum variation in the length of the Autoclave Aerated Concrete Block shall not be more than plus/minus 5mm and maximum variation in the height and width of Autoclave Aerated Concrete Block, not more than plus/minus 3mm.

The faces of Autoclave Aerated Concrete Block shall be flat & Rectangular, opposite faces shall be parallel and all arises shall be square. The bedding surfaces shall be at right angle to the face of the Blocks.

The Autoclave Aerated Concrete Block with special faces shall be manufactured and supplied if so specified.

The autoclaved Autoclave Aerated Concrete Block shall be classified in two grades according to their compressive strength as indicated in table

Materials

Cement complying with any of the Indian Standard may be used as per the direction of the manufacturer.

Use of Fly ash conforming to IS 3812-1981 may be permitted to a limit of 20% in cement conforming to IS 269-1976.

The lime shall satisfy the requirement for class C lime specified as IS 712-1973.

The aggregate used for the manufacture of Autoclave Aerated Concrete Block shall conform to the following requirements
(a) Sand-Conforming to IS 383-1970 except for the grading which may be made to suit the product and silica content shall not be less than 80%.
(b) Fly ash – Conforming to IS 3812-1981 with loss on ignition not more than 6%.

The water used in the manufacture of Autoclave Aerated Concrete Block shall be free from matter harmful to concrete or reinforcement or matter likely to cause efflorescence in the block and shall meet the requirements of IS 456-2000.

Additives and Admixtures may be added either as additives to the cement during
manufacturing or as additive or admixtures to the concrete mix. Additive or admixtures used in the manufacture of concrete block may be
(a) Accelerating , water reducing and air –entraining admixtures conforming to IS 9103-1979
(b) Water proofing agent conforming to IS 2645-1975
(c) Colouring pigments

Physical requirements
All Autoclave Aerated Concrete Block shall be sound, free of cracks or other defects which interfere with the proper placing of block units, impair the strength or performance of the construction.

Where block units are to be used in exposed wall construction, the face or faces that are to be exposed shall be free of chips, cracks or other imperfections except that if not more than 5% of a consignment contains slight cracks or small chippings not larger than 25mm, this shall not be deemed grounds for rejection.

Dimensions- The overall dimension and tolerances of the block units when measured shall be in accordance with para   (M-AUTOCLAVED AERATED CONCRETE BLOCK MASONRY WORK,  Dimensions & Tolerances).

Block Density - The Block density shall conform to the requirements specified in table given below when tested in accordance with (The block density shall be determined in the manner described in IS 6441 (part-1) -1972).
                                                               Table - A


Compressive Strength - The min. compressive strength being the average of twelve block units shall be as prescribed in table A (as above) , when tested in accordance with IS 6441 ( part-5) -1972.

Thermal Conductivity - The thermal conductivity shall be not exceed the values specified in table A (as above)  when tested in accordance with IS 3346 -1980.

Drying Shrinkage – the drying shrinkage shall be not more than 0 .05% for grade –1 block and 0.10% for grade-2 block when tested in accordance with  IS 6441 ( part-2) -1972.

Tests

1. Block Density- The block density shall be determined in the manner described in IS 6441 ( part-1) -1972
2. Compressive Strength- The compressive strength of block shall be determined in accordance with IS 6441 ( part-5) -1972
3. Thermal Conductivity- The thermal conductivity of block shall be determined in accordance with IS 3346 -1980
4. Drying Shrinkages-The drying shrinkage of block shall be determined in the manner described in IS 6441 ( part-2) -1972.


 Sampling
Lot - In any consignment, all the blocks of the same size and from the same batch of
manufacture shall be grouped together into a minimum number of groups of 10000 blocks or less.Each such group shall constitute a lot.

From each lot, a sample of 24 blocks shall be selected at random. The required numbers of Blocks shall be taken at regular intervals during the loading of the vehicle or unloading the vehicles depending on whether sample is taken before delivery or after delivery. When this is not practicable,
sample shall be taken from the stack in which case the required number of blocks shall be taken at random from across the top of the stacks, the sides accessible and from the interior of the stacks by opening trenches from the top.

The sample of blocks shall be marked for future identification of the consignment it represents.The blocks shall be kept under cover and protected from extreme conditions of temperature, relative
humidity and wind until they are required for test. The tests shall be undertaken as soon as practicable after the sample has been taken.

Number of tests

All the 24 Blocks shall be checked for dimensions and inspected for visual defects.

Out of the 24 blocks, 12 blocks shall be subjected to the test for compressive strength, 3 blocks to the test for density, 3 blocks to the test for thermal conductivity and 3 blocks to the test for drying shrinkage. The remaining 3 blocks shall be reserved for re-test for drying shrinkage if a
need arises.

The samples of AAC blocks (each sample consisting of 6 specimen) shall be chosen randomly from the lot procured and tested for various parameters specified in para 6 above. One samples shall be tested for every 100 cum or part thereof. However, minimum one sample shall be tested from each lot received at site if the quantity procured in the lot is less than 100 cum. If required, Engineer-in-Charge or his authorized representative shall inspect the factory during production of
the material for this work and also collect samples (of materials used for making AAC blocks and precast AAC blocks) from the factory itself. The contractor shall consider this contingency also while placing the order with one of the approved firms. Nothing extra shall be payable on this account.

Criteria for conformity
The number of blocks with dimensions outside the tolerance limit and or with visual defects, among those inspected, shall not be more than two.

For density, the mean value shall be within the range specified in Table A (As above)

For compressive strength, the mean value, say X shall be determined. The test results
shall be grouped into groups of 4, individual values of ranges shall be determined, the average range a calculated from these values and shall satisfy the following condition:
X- 0.6 R> minimum value specified in Table A (As above).

For thermal conductivity, the mean value shall be equal to or less than the value specified in Table A.

For drying shrinkage, all the test specimens shall satisfy the requirements of the test. If one or more specimens fail to satisfy the requirements, the remaining 3 blocks shall be subjected to these tests. All these blocks shall satisfy the requirements.

Manufacturer’s Certificate

The manufacturer shall satisfy himself that the masonry units conform to the requirements of this specification and, if requested, shall supply a certificate to this effect to the purchaser or his representative.

Independent Test
If the purchaser or his representative requires independent tests, the samples shall be taken before or immediately after delivery, at the option of the purchaser or his representative and the tests shall be carried out in accordance with this specification.

The manufacturer shall supply free of charge the units required for testing.

Storage

General requirements of storage of autoclaved cellular (aerated) concrete blocks shall be as described in IS : 4082-1977*.

Marking

Each lot of concrete masonry units manufactured in accordance with this specification shall be suitably marked with information-
(i) The identification of the manufacture
(ii) The grade and block density of the unit
(iii) The month and year of manufacturing
Each block may also be marked with the ISI Certification mark.

The R.C C bend shall be provided on 150mm /230mm/300mm thick masonry to increase the strength and compatibility . The RCC bend shall be provided at sill level and at
lintel level over throughout the wall. This thickness of the bend shall be approved by the Engineer in charge or as specified in drawing. The payment of RCC bend and reinforcement shall be paid separately.
Autoclave Aerated Concrete Block masonry shall be provided with polymer modified adhesive mortar.The polymer modified adhesive mortar shall be provided @ 30 kg per cum or with cement mortar 1:4 (1 cement : 4 coarse sand).

Autoclave Aerated Concrete Block with 100 mm thick masonry shall be provided with two number 6mm dia reinforcement steel bar at every third course. The payment of reinforcement shall be paid separately.
6.14.16. Autoclaved Aerated Concrete Block confirming the IS Code – 2185 (Part-3) 1984
(Reaffirmed 2005).

Measurements

Autoclave Aerated Concrete Block Masonry shall be measured in cubic metres unless
otherwise specified.
Any extra work over the specified dimensions shall be ignored. Dimensions shall be measured correct to the nearest 0.01 metre. ie. 1 cm. Areas shall be calculated to the nearest 0.01 sqm and the cubic contents shall be worked out to the nearest 0.01 cubic metres.

Note : (i) Autoclave Aerated Concrete Block work in parapet walls, mumty, lift machine room and water tanks constructed on the roof upto 1.2 m height above roof shall be measured together with the corresponding work of the floor next below.

No deductions or additions shall be done and no extra payment made for the following:

Note: Where minimum area is defined for deduction of an opening, void or both, such areas shall refer only to
opening or void within the space measured.
(a) Ends of dissimilar materials (that is, joists, beams, lintels, posts, girders, rafters, purlins, trusses, corbels, steps etc.); up to 0.1 m2 in section;
(b) Opening up to 0.1 m2 in area (see Note);
(c) Wall plates, bed plates, and bearing of slabs, chajjas and the like, where thickness does not exceed 10 cm and bearing does not extend over the full thickness of wall;
(d) Cement concrete blocks as for hold fasts and holding down bolts;
(e) Iron fixtures, such as wall ties, pipes upto 300 mm diameter and hold fasts for doors and windows;
(f) Chases of section not exceeding 50 cm in girth; and
(g) Bearing portion of drip course, bearing of moulding and cornice.

Note: In calculating area of an opening, any separate lintel or sills shall be included with the size of the opening but end portions of lintel shall be excluded. Extra width of rebated reveals, if any, shall also be excluded.

String courses, projecting pilasters, aprons, sills and other projections shall be fully described and measured separately in running metres stating dimensions of each projection.

Square or rectangular pillars shall be measured separately in cubic metres

Circular pillars shall be measured separately in cubic metres as per actual dimensions

Autoclave Aerated Concrete Block work curved on plan shall be measured like the block work in straight walls and shall include all cutting and wastage of blocks, tapered vertical joints and use of extra
mortar, if any. Block work curved on plan to a mean radius not exceeding six metres shall be measured separately and extra shall be payable over the rates for block work in straight walls. Nothing extra shall be payable if the mean radius of the block work curved in plan exceeds six metres.

Tapered walls shall be measured net as walls and extra payment shall be allowed for making tapered surface for block work in walls.

Rate

The rate shall include the cost of materials and labour required for all the operations described. The rate shall also include the following:
(a) Raking out joints or finishing joints flush as the work proceeds;
(b) Preparing tops of existing walls and the like for raising further new block work.
(c) Rough cutting and waste for forming gables, splays at eaves and the like.
(d) Leaving holes for pipes upto 150 mm dia. and encasing hold fasts etc.
(e) Rough cutting and waste for block work curved in plan and for backing to stone or other types off acing.
(f) Embedding in ends of beams, joists, slabs, lintels, sills, trusses etc.
(g) Bedding wall plates, lintels, sills, roof tiles, corrugated sheets, etc. in or on walls if not covered in respective items
(h) Leaving chases of section not exceeding 50 cm in girth or 350 sq cm in cross-section; and
(i) Block on edge courses, cut brick corners, splays reveals, cavity walls, brick works curved on plan to a mean radius exceeding six metres.


APPENDIX - A


TEST FOR DIMENSIONAL TOLERANCE

A -1. Sampling

Sampling: For carrying out compressive strength, water absorption, efflorescence and dimensional tests, the samples of bricks shall be taken at random according to the size of lot as given in Table -3.
The sample thus taken shall be stored in a dry place until tests are made. For the purpose of sampling, the following definition shall apply.
(a) Lot: A collection of bricks of same class and size, manufactured under relatively similar conditions of production. For the purpose of sampling a lot shall contain a maximum, of 50,000 bricks.
In case a consignment has bricks more than 50,000 of the same classification and size and manufactured under relatively similar conditions of production, it shall be divided into lots of 50,000 bricks or part thereof.
(b) Sample: A collection of bricks selected for inspection and/or testing from a lot to reach the decision regarding the acceptance or rejection of the lot.
(c) Defective: A brick failing to meet one or more of the specified requirements.

 The samples shall be taken as below:
(i) Sampling from a Stack: When it is necessary to take a sample from a stack, the stack shall be divided into a number of real or imaginary sections and the required number of bricks drawn from each section. For this purpose bricks in the upper layers of the stack shall be removed to enable
units to be sampled from places within the stack.
Note: For other methods of sampling i.e. sampling in motion and sampling from lorries or trucks, IS :5454 may be referred.
Scale of sampling and criteria for conformity for visual and dimensional characteristics:—
Visual characteristics: The bricks shall be selected and inspected for ascertaining their conformity to the requirements of the relevant specification.
The number of bricks to be selected from a lot shall depend on the size of lot and shall be in accordance of Col. 1 and 2 of Table - 3 for visual characteristics in all cases and dimensional characteristics if specified for individual bricks.
(ii) Visual Characteristics: All the bricks selected above in accordance with Col. 1 and 2 of Table -3 shall be examined for visual characteristics. If the number of defective bricks found in the sample is
less than or equal to the corresponding number as specified in Col. 3 of Table - 3 the lot shall beconsidered as satisfying the requirements of visual characteristics, otherwise the lot shall be deemed as not having met the visual requirements.
(iii) Dimensional Characteristics: The number of bricks to be selected for inspecting thedimensions and tolerance shall be in accordance with Col. 1 and 4 of Table -below . These bricks will be divided into groups of 20 bricks at random and each of the group of 20 bricks thus formed will be tested for all the dimensions and tolerances. A lot shall be considered having found meeting the requirements of dimensions and tolerance if none of the groups of bricks inspected fails to meet the specified requirements
                                                                 Table - 3

Note: In case the lot contains 2000 or less bricks the sampling shall be as per decision of the Engineer-in-Charge.
(iv) Scale of Sampling and Criteria for Physical Characteristics: The lot which has been found satisfactory in respect of visual and dimensional requirements shall be next tested for physical characteristics like compressive strength, water absorption, efflorescence as specified in relevant material specification. The bricks for this purpose shall be taken at random from those already selected above. The number of bricks to be selected for each of these characteristics shall be in accordance with relevant columns of Table -4. 

                                                                  Table -4

Note: In case the lot contains 2000 or less bricks, the sampling shall be as per decision of Engineer-in-Charge.

(v) A lot shall be considered having satisfied the requirements of physical characteristics if the condition stipulated here in are all satisfied.
(a) From the test results for compressive strength, the average shall be calculated and shall satisfy the requirements specified in relevant material specification.
Note: In case any of the test results for compressive strength exceeds the upper limit for the class of bricks, the same shall be limited to the upper limit of the class for the purpose of averaging.
(b) Wherever specified in the material specification, the compressive strength of any individual bricks tested in the sample shall not fall below the minimum average compressive strength specified for the corresponding class of brick by more than 20 percent.
(c) From the test results for water absorption, the average for the bricks in the sample shall be calculated and shall satisfy the relevant requirements specification in material specification.
(d) The number of bricks failing to satisfy the requirements of the efflorescence specified in the relevant specification should not be more than the permissible no. of defectives given in Col.3 of Table-4.

A -2. Procedure

All the blisters, loose particles of clay and small projections shall be removed from the surface of  bricks. Each specimen of 20 bricks shall then be arranged upon a level surface successively as  indicated in Fig. A, B and C of para A-4 below in contact with each other and in straight line. The  overall length of the assembled bricks (20 Nos) shall be measured with a steel tape sufficiently long to  measure the whole row at one stretch.

A-3. Tolerance

The actual dimensions of bricks when tested as described in A-2 shall be within the following limits
per 20 bricks.



A-4. Criteria for Conformity

A lot shall be considered conforming to the requirements of dimensions and tolerances if all the  groups of bricks are tested to meet the specified requirements.





APPENDIX - B



TEST FOR COMPRESSIVE STRENGTH

B-1. Specimen

Five whole bricks shall be taken from the samples as specimens for this test. Length and width of each specimen shall be measured correct to 1 mm.

B-2. Apparatus

The apparatus consists of compression testing machine, the compression plate of which shall have a ball seating in the form of portion of a sphere the centre of which shall coincide with the centre
of the plate.

B-3. Procedure

(a) Pre-conditioning: The specimen shall be immersed in the water for 24 hours at 250
C to 290C. Any surplus moisture shall be allowed to drain at room temperature. The frog of the bricks should be filled flush with mortar 1:3 (1 cement : 3 clean coarse sand of grade 3 mm and down) and shall be kept under damp jute bags for 24 hours, after that these shall be immersed in clean water for three days.
After removal from water, the bricks shall be wiped out of any traces of moisture.

(b) Actual Testing: Specimen shall be placed with flat faces horizontal and mortar filled face upward between three 3 ply plywood sheets each of thickness 3 mm and carefully centred between plates of the testing machine. Plaster of Paris can also be used in place of plywood sheets to ensure a uniform surface.
Load shall be applied carefully axially at uniform rate of 14 N/mm2 per minute till the failure of the specimen occurs.

B-4. Reporting the Test Results
The compressive strength of each specimen shall be calculated in N/mm2 as under :

Compressive Strength ={Maximum load at failure (in N) / Area of Specimen (in sq mm)}

In case the compressive strength of any individual brick tested exceeds the upper limit of the average compressive strength specified for the corresponding class of brick, the same shall be limited to the upper limit of the class specified in table below  for the purpose of calculating the average compressive strength. Compressive strength of all the individual bricks comprising the sample shall be averaged and reported.


B-5. Criteria for Conformity

A lot shall be considered having satisfied the requirements of average compressive strength if the average compressive strength specified in Table above  for the corresponding class of brick tested is not below the minimum average compressive strength specified for the corresponding class of bricks by more than 20 per cent.



APPENDIX - C

TEST FOR WATER ABSORPTION

C-1. No. of Specimen
Five whole bricks shall be taken from samples as specimen for this test.

C-2. Apparatus
A balance required for this test shall be sensitive to weigh 0.1 percent of the weight of the specimen.

C-3.Procedure
(a) Pre-conditioning: The specimen shall be allowed to dry in a ventilated oven at a 110°C to 115°C till it attains a substantially constant weight. If the specimen is known to be relatively dry, this  would be accomplished in 48 hours, if the specimen is wet, several additional hours may be  required to attain a constant weight. It shall be allowed to cool at room temperature. In a ventilated room, properly separated bricks will require four hours for cooling, unless electric fan  passes air over them continuously in which case two hours may suffice.
The cooled specimen shall be weigh (W1) a warm specimen shall not be used for this purpose.
(b) Actual Testing: Specimen shall be completely dried before immersion in the water. It shall be kept in clean water at a temperature of 27°C ± 2°C for 24 hours. Specimen shall be wiped out of  the traces of water with a damp cloth after removing from the water and then shall be weighed
within three minutes after removing from water (W2).

C-4. Reporting the Test Results
The water absorption of each specimen shall be calculated as follows and the average of five tests shall be reported.
WaterAbsorption ={ (W2– W1) / W1 } * 100

C-5. Criteria for Conformity
A lot shall be considered having satisfied the requirements of water absorption if the average water absorption is not more than 20% by weight.



APPENDIX - D

TEST FOR EFFLORESCENCE

D-1. No. of Specimen
Five whole bricks shall be taken as specimen for this test.

D-2. Apparatus
Apparatus required for this test shall be a shallow flat bottom dish containing distilled water.

D-3. Procedure (actual testing)
The brick shall be placed vertically in the dish with 2.5 cm immersed in the water. The room shall be  warm (18ºC to 30ºC) and well ventilated. The bricks should not be removed until it absorbs whole water. 
When the whole water is absorbed and the brick appears to be dry, place a similar quantity of water in that  dish and allow it to evaporate as before. The brick shall be examined after the second evaporation.

D-4. Reporting the Test Results
The rating to efflorescence in ascending order shall be reported as ‘NIL’, ‘SLIGHT’, ‘MODERATE’,‘HEAVY’ or ‘SERIOUS’ in accordance with the following :
(a) NIL: When there is no perceptible deposit of efflorescence.
(b) SLIGHT: When not more than 10 per cent of the area of the brick is covered with a thin deposit of salts.
(c) MODERATE: When there is heavier deposit and covering upto 50% of the area of the brick surface  but unaccompanied by powdering or flaking of the surface.
(d) HEAVY: When there is a heavy deposit of salts covering 50% or more of the brick surface but unaccompanied by powdering or flaking of the surface.
(e) SERIOUS: When there is heavy deposit of salts, accompanied powdering and/or flaking of the surface and tending to increase in the repeated wetting of the specimen.

D-5. Criteria for Conformity
A lot be considered having satisfied the requirements of efflorescence if for 4 out of the specimen of 5 bricks, the rating of efflorescence is not beyond “Moderate.


Thanks a lot
Mukesh Kumar
Gyan of engineering
Source of Content  : CPWD SPECIFICATIONS 2019

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