SECTION - 3
BRICK AND CEMENT CONCRETE BLOCK WORK
3.1 SCOPE
This section consists of construction of brick/ cement concrete block work walls
of any thickness with first class hand-mould and/or machine pressed
bricks/cement concrete blocks with the specified ratio of cement mortar in
foundation, plinth superstructure or for any other structure as directed by the
Engineer, or shown in the Bid Schedule. The Contractor shall furnish all
materials and all other requirements to produce finished brick/block work.
Brick/block work and materials for brick/block work shall be in strict
accordance with this section of the specifications and applicable drawings and
subject to the terms and conditions of the Contract.
3.2 MATERIALS
3.2.1 Portland Cement
Portland cement shall conform to the stipulations and requirements set forth in
Section "CONCRETE".
3.2.2 Mortar Sand
Sand for mortar used in construction of brickwork/blockwork required under
these Specifications shall be furnished by the Contractor in accordance with the
provisions and in conformity with the stipulations and requirements of ASTM
Designation C144-70 or latest revision and shall have a fineness modulus
between 1.6 to 2.5.
3.2.3 Water
The water used in the preparation of mortar shall be free from objectionable
quantities of silt, organic matter, alkali salts and other impurities and it will be
tested in accordance with BS-3148 and approved by the Engineer at the
Contractor's cost.
3.2.4 Aggregate
Aggregates for mortar shall comply with the requirements of ASTM C144. Sand
that has been in contact with seawater shall not be used unless it has been
thoroughly washed to the satisfaction of the Engineer.
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3.2.5 Additives
Additives where used, shall be proprietary products used in the proportions and
manner recommended by the manufacturer. The additives shall in no way
adversely affect the mortar strength or contain chemicals, which may e harmful
to other building materials. To add gypsum to cement is strictly forbidden.
3.3 MORTAR AND GROUT
Materials for mortar, sand binding agent and water shall be mixed by volume for
at least 3 minutes with the minimum amount of water to produce a correctly
mixed mortar or grout of workable consistency in a mechanical batch mixer. For
small jobs, hand mixing may be permitted, the ingredients being mixed with
sufficient water to produce a correctly mixed workable mortar. Mortar used in
masonry construction shall conform to ASTM C-270 standard.
Mortars shall be mixed in batches, which can be used within a period before the
setting process commences. Once a mix begins drying off, it shall be rejected.
No ingredients shall be added to it once the setting process has begun. Mortar
shall not be retained for more than 30 minutes and shall be constantly worked
over with hoe or shovel until used.
3.4 MORTAR BATCHING
Methods or equipment used for mixing mortar shall be such as will accurately
determine and control the amount of each separate ingredient entering into the
mortar and shall be subject to the approval of the Engineer. If a mixer is used it
shall be of approved design and the mixing time after the ingredients are in the
mixer, except for the full amount of water, shall not be less than two minutes.
Mortar shall be mixed only in sufficient quantities for immediate use and all
mortar not used within 30 minutes after addition of water to the mix shall be
wasted. Retampering of mortar shall not be allowed. Mixing pans and troughs
shall be thoroughly cleaned and washed at the end of each day's work.
3.5 SCAFFOLDING
Contractor shall provide safe scaffolding of adequate strength for use of
workmen at all levels and heights at his own expense. Scaffolding which is
unsafe in the opinion of the Engineer shall not be used until it has strengthened
and made safe for use of workmen. Cost of scaffolding etc., shall be included by
the Contractor in the unit rate for masonry items.
Damage to masonry from scaffolding or from any other object shall be repaired
by the Contractor at his own cost.
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3.6. JOINTING
Jointing is the forming of joints as work proceeds. Joints shall be as follows:
3.6.1 Exterior exposed joints shall be tightly formed to a weather joint with the point
of the trowel.
3.6.2 Interior exposed joints shall be tightly formed to a concave joints.
3.6.3 Joints which are subsequently covered with plaster or other finish materials shall
be struck flush.
3.7 BRICKS
The bricks used shall be of standard size (9"x4.5"x3") first class well burnt,
uniform in shape, size, texture, colour and should produce a ringing sound when
struck. The bricks shall be free from flaws, cracks, chips, stone nodules of lime
or kan-kar or any other blemishes. The brick shall not absorb more than one
sixth of its weight when soaked in water for one hour. Compressive strength
shall not be less than of 1400 psi. Bricks over burnt, under burnt vitrified and
irregular shall not be used. Bricks of uniform size shall be used throughout the
work and source of supply shall not be diversified.
3.7.1 Soaking
Before use all bricks shall be soaked in clean water in tanks or pits for at-least
two hours.
3.7.2 Laying of Bricks
All brickwork shall be skillfully laid with level courses, uniform joints, square
corners, plumb verticals and true surfaces except when otherwise shown on the
Drawings or directed by the Engineer. Brickwork will be of best standard of
workmanship obtainable and objectionable offsets in the brickwork shall be
avoided. Smoothest practicable finished surface of the brickwork shall be
ensured. Unless otherwise specified bricks shall be laid in English Bond with
frogs (Manufacturer's marks) upward.
All horizontal joints shall be parallel and truly level. Vertical joints in alternate
coarses shall come directly over one another. Thickness of joints unless
otherwise specified shall not be less than 1/4 of an inch and not more than 3/8 of
an inch. The height of 4 coarses and 3 joints as laid shall not exceed by more
than 1 inch the height of 4 bricks as piled one upon the other.
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3.7.3 Curing
All brick work involving use of cement shall be cured by water curing or other
acceptable methods. The Engineer shall approve all methods and operations of
the Contractor in curing different portions of work.
When curing by water brickwork shall be kept wet for at least 14 days by
covering with water saturated materials or by a system of perforated pipes,
mechanical sprinklers, porous hose, ponding or by any other approved method
which will keep all surfaces to be cured continuously wet. Water used for curing
shall meet the requirements given in Clause 3.2 of these specifications.
3.8 BLOCKS
Cement, aggregates and water for concrete blocks shall conform to the
requirements as specified in the section for plain and reinforced concrete or as
approved by the Engineer.
3.8.1 Concrete Block Making
3.8.1.1 The solid and hollow blocks as and where used by planning, shall be machine
moulded. The block making machines shall be of the standard approved by the
Engineer. They shall be operated according to the instructions laid down by the
manufactures.
3.8.1.2 The blocks shall be continuously water cured by sprinkling water for a minimum
of 10 days and covered between sprinkling operations with 4 mils thick
polyethylene sheeting. After the 10 days water curing period the blocks shall be
air dried. Under no circumstances will blocks be used in the work until they are
completely dry. During curing period no surfaces of the block will be allowed to
dry.
3.8.1.3 Cured concrete blocks shall be stored off the ground, stacked on level platforms,
which allow air circulation under stacked units. Units shall be covered and
protected against wetting.
3.8.1.4 Care shall be exercised in the handling of all concrete blocks. No damaged
blocks shall be used in the work.
3.8.1.5 The blocks cast on different dates shall be stacked separately and must be labeled
showing the date on which they were cast.
3.8.2 Properties of Blocks
3.8.2.1 All blocks shall be of size and shape required to complete the work shown in the
Drawings or as instructed by the Engineer.
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3.8.2.2 The cement, sand and coarse aggregate shall be volume batched and their
proportion may be adjusted so as to provide the concrete of the required strength
when tested and shall be mixed in a concrete mixer.
3.8.2.3 All blocks shall conform to ASTM C 145 standard. The compressive strength
based on gross area shall be minimum 8.30 MPa for an average of 3 blocks and
minimum 7.0 MPa for lowest individual blocks with 28 days after casting
Cement Concrete Solid Blocks.
3.8.2.4 The Contractor shall provide test certificates show in the average minimum
crushing strength of the blocks prior to the commencement of the construction.
Further test certificates shall be provided as required by the Engineer, to ensure
that all batches of block strengths are to be determined in accordance with
ASTM C- 140 Standard.
3.8.2.5 The test shall be carried out by a laboratory approved by the Engineer. Evidence
shall be produced that the block manufacturer has an efficient method of quality
control. The Engineer will require to test samples of blocks periodically and the
Contractor shall make necessary arrangements accordingly. The method of
sampling for all test shall be in accordance with ASTM C-140.
3.8.2.6 All properties or specifications of blocks, not explain in these Specifications or
ASTM C 145 shall comply with the requirements of PS 419, as directed by the
Engineer.
3.8.3 Soluble Salt Content
For exposed block work, the contents by weight percent of soluble sulphate,
calcium, magnesium, potassium and sodium radicals, shall not exceed 0.30,
0.10, 0.30, 0.03 percent respectively when ascertained in accordance with BS
3921, at the cost of the Contractor.
3.8.4 Erection
3.8.4.1 Block shall be laid true to line, level and laid in accurately spaced courses in
stretcher bond with vertical joints of each course located at centre of units in
alternate courses below. Vertical joints shall be buttered in the entire height of
blocks. Each course shall be bonded. Courses of block shall be kept plumb
throughout and corner reveals shall be true and in plumb.
Standard with of mortar joints for both horizontal and vertical joints shall be
7/16 inch (maximum). Mortar joints in wall shall have full mortar coverage on
vertical and horizontal faces between the blocks. Mortar joints on wall including
struck joints, shall be thoroughly compacted and pressed tight against the edges
of the blocks with proper tools. Blocks terminating against soffits of beam or
slab construction shall be wedged tight with wedges and the joints shall be
packed solidly with mortar between the top of the block and the bottom of slab
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or beam. Control expansion joints shall e kept free from mortar or other debris.
Unless otherwise shown on the drawings or specified by the Engineer, the spaces
around door frames and other material or built in items shall be solidly filled
with mortar. Spaces around the door and window hold fasts shall be filled in
with Class C concrete. Work required to be built in with masonry including door
frame anchors, wall plugs, dovetail anchors and accessories shall be built in as
the erection progresses.
3.8.4.2 The block work shall be carried out in a uniform manner and no portion shall be
carried more than one metre above the adjoining one at any times. All masonry
shall be kept strictly true and square and the whole properly bonded together and
levelled round each floor.
3.8.4.3 Sleeves, Chases, holes, sinking and mortices for other trades shall be correctly
located and formed to the sizes as required by the relevant trades. Chiselling of
completed walls or the formation of holes shall only be carried out with the
approval of the Engineer.
3.8.4.4 Walls of blocks indicated as being non-load bearing shall be constructed on
insitu concrete floor slab unit after the floor formwork is struck and the concrete
has obtained sufficient strength to support their weight. Toothing into load-
bearing walls shall not be permitted.
3.8.4.5 All bolts, anchors, ties, pipe sleeves, flushing metal attachments lintels and the
like required to be built into the work shall be correctly inserted and executed as
the work proceeds.
3.8.4.6 Walls or partitions abutting concrete columns or walls shall be securely anchored
and tied with metal anchors or ties at not more than 18 inches vertical centres.
Wall ties cast in with concrete shall be bent down after the removal of form
work and shall be securely jointed into the mortar beds of walling.
3.8.5 Curing and Repairs
3.8.5.1 All block masonry shall be water cured and shall be kept wet for at least seven
days, by an approved method, which will keep all surfaces to be cured
continuously wet. Water used for curing shall meet the requirements of
specifications for water used in the manufacture of blocks.
3.8.5.2 Tolerances
All block work shall be erected plumb and true to line and level with the
maximum variation in any storey height or any length of wall being one mm in
one metre. The maximum tolerance in the length, height or width of any single
masonry wall shall be + 1/8 inch.
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3.8.5.3 If, after the completion of any block masonry work, the block is not in alignment
or level, or does not, conform to the lines and grades shown on the Drawings or
shows a defective surface, it shall be removed and replaced by the Contractor at
his expense unless the Engineer grants permission, in writing, to patch or replace
the defective area.
3.9 MEASUREMENT AND PAYMENT
3.9.1 Material (Brick and cement concrete block work )
Measurement and payment for brick/cement concrete block work shall be made
in accordance with the provisions given hereafter.
3.9.1.1 Method of Measurement
Measurement for brick/block work shall include number of cubic ft. of
brick/block work provided within the limits as shown on the Drawings or as
directed by the Engineer.
3.9.1.2 Basis of Payment
Payment for brick/block work shall be made at the contract unit price per cubic
feet. Payment shall constitute full compensation for furnishing all materials,
equipment and labour including all incidentals necessary to complete the work:
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Pay Item Description Unit
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3.1 Provide and Lay Brick Masonry Cft.
with cement sand mortar in
foundation and super structures.
3.2 Provide and Lay Block Masonry Cft.
with cement sand mortar in
foundation and super structures.
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