Federal Electricity & Water Authority Water Directorate ... · PDF file5.1 Concrete Blocks 5.2 Calcium Silicate Block ... DUBAI Order: Document: MWA_PRO ... Premoulded closed-cell

WAM

Client: FEDERAL ELECTRICITY AND WATER AUTHORITY (FEWA) Project: STANDARD SPECIFICATIONS FOR WATER WORKS

Engineer WATER DIRECTORATE - WATER ASSET MANAGEMENT DEPARTMENT

Title: Technical Terms / Chapter-4 / Engineering Specifications / Civil Engineering Works Specification

CS12-MASONRY / PLASTERING / SCREED

Office:

DUBAI Order: Document:

MWA_PRO_07/WAM-04-CS12 Rev: OCT/2014 sheet: 1 of: 20

Federal Electricity & Water Authority

Water Directorate

Asset Management Department

STANDARD SPECIFICATIONS

FOR WATER WORKS

TECHNICAL TERMS

Chapter – 4

Engineering Specifications

[C-Civil Engineering Works Specifications]

CS12-Masonry/Plastering/Screed

WAM


Engineer WATER DIRECTORATE - ASSET MANAGEMENT DEPARTMENT



Office: DUBAI Order: Document: MWA_PRO_07/WAM-04-CS12 Rev:

OCT/2014 sheet: 2 of: 20

CS12-Masonry/Plastering/Screed TABLE OF CONTENT

A. MASONRY

9. GENERAL

10. STANDARDS AND CODES (To include all latest amendments)

11. SAMPLES

12. TEST RESULTS

13. MATERIALS

5.1 Concrete Blocks

5.2 Calcium Silicate Block Work

5.3 Mortar

5.4 Joint Filling Sealant

5.5 Wall Ties and Mesh Reinforcement

5.6 Concrete Bricks

5.7 Special Blocks and Thermal Blocks

5.8 Pre-cast Claustra Blocks

5.9 Miscellaneous Materials

6. MANUFACTURE

7. QUALITY ASSURANCE

7.1 Construction requirement

7.2 Mock-Up

7.3 Field Quality Control

7.4 Damp- Proof Course

8. WORKMANSHIP

9. REINFORCED CONCRETE BLOCK WALL STIFFENERS

10. ANCILLARY WORKS

11. CONSTRUCTION TOLERANCES

12. SUBMITTALS

13. JOB CONDITIONS

14. CURING

15. REPAIR, POINTING AND CLEANING

16. BUILDERS WORK

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B. PLASTERING

1. GENERAL


3. SAMPLES

4. MATERIALS

4.1 Sand and Cement Plaster

4.1.1 Cement

4.1.2 Sand

4.1.3 Water

4.1.4 Admixtures and Colouring Agents

4.2 Job Conditions

5. WORKMANSHIP

5.1 General

5.2 Preparation

5.3 Plastering

5.3 Expanded Metal Lathing/Plaster Beads/Stops/Angles, etc..

5.3.1 Plaster Stops Beads

5.3.2 Angle Beads

5.3.3 Concrete, Blockwork and Masonry Backgrounds

5.4 Internal Plaster

5.5 External Plaster

5.6 Reveals, Jambs and Soffits

5.7 Rough Cast

5.8 Mixing

5.9 Finishes

5.10 Curing

5.11 Cutting and Patching

5.12 Cleaning and Protection

C. SCREEDS AND TOPPINGS

1. GENERAL

2. SUBMITTALS

3. Materials and Products

4. Workmanship

4.1 General

4.2 Mixing

4.3 Joints

4.4 Compaction

4.5 Tolerances

4.6 Finishes

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CS12-Masonry/Plastering/Screed

A. MASONRY 1. GENERAL

This work shall consist of the supply of all materials and the execution of all concrete block work and partition construction including forming all the openings for doors, windows, ventilators, etc. and all builders work for all services, etc. in accordance with the Drawings and Specifications.


B.S. 12 Specification for ordinary and rapid hardening Portland cement. B.S. 105 Expanded Metal (steel) for general purpose B.S. 743 Materials for damp proof courses B.S. 890 Specification for building limes, hydrated lime, (powdered) quick lime putty

etc. B.S. 1200 Specification for building sand B.S. 1243 Wall ties B.S. 2028 Precast concrete blocks B.S. 4254 Specification for two-part polysulphide based sealants B.S. 4551 Test methods for mortars B.S. 5224 Specification for masonry cement B.S. 5828 Code of Practice for the structural use of masonry B.S. 6073 Specification for precast concrete masonry, material tolerances, etc. B.S. 8050 Part 3 - Code of Practice for masonry walling C.P. 121 Walling C.P. 121 Part 1 - Brick and block Masonry C.P. 122 Wall and partitions of blocks and slabs

2. SAMPLES

The Contractor shall submit representative samples for the different sizes of concrete blocks (hollow and solid) as required.All tests shall be performed by the Contractor at his own expense as directed by the Engineer.

3. TEST RESULTS

The Contractor shall submit compressive strength test results to FEWA/ Engineer for each type of concrete block for approval before supplying to the Site.

Testing of blocks shall be in accordance with the appropriate B.S. and the Contractor shall submit

results of testing to FEWA/ Engineer at regular but not less than fortnightly intervals. Where blocks are supplied by an approved block manufacturer, test certificates where required by FEWA/ Engineer will be obtained by the Contractor from the manufacturer.

Any batch of precast concrete blocks shall be subject to the testing of four blocks selected at

random.

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5. MATERIALS 5.1 Concrete Blocks

The cement, water, sand and aggregates used shall meet the requirements of the section of the Specification relating to Concrete and Reinforcements.Concrete blocks shall be obtained from approved local manufactures. They shall be sound, of uniform size, shape and texture. Concrete blocks may be solid, insulated or hollow, depending upon their use.

Solid concrete blocks will have a dry density higher than 1900 kg/m3 and a minimum strength of

100 kg/cm2. Hollow concrete, non load bearing, blocks will have a density higher than 1200 kg/m3 and a strength of 55 kg/cm2.Water absorption shall be 20% or less of dry weight.

Blocks in contact with the ground shall be solid sulphate resisting concrete blocks coated with thick black bitumen or tar composition unless otherwise stated.The basic dimensions of concrete blocks shall be such that the thickness of walls shown on Drawings will be satisfied. Blocks shall have the following dimensions: Height - 200 mm +/- 1% tolerance Length - 400 mm +/- 0.5% tolerance Width - * +/- 1% tolerance * The nominal width is indicated on the Approved drawings.

Concrete blocks shall meet the requirements of BS 2028 and BS 6073. All blocks that do not conform to requirements will be rejected.

Visible headers shall be plane and the colour and texture of concrete shall be compared such that it

is regular, cement grey and slightly granulated free of all latence.Dimensional tolerances from – 2 mm to 0 mm on all dimensions. Planeity of the faces : camber 1 mm maximum.

Any block that is chipped, even slightly cracked or irregular shall be refused. Edges are to be

perfectly straight.The cement content in the concrete mix of the manufactured block shall not be less than 200 kg./m3.

5.2 Calcium Silicate Block Work Precast calcium silicate blocks shall be brought only from the approved supplier. Block size shall be of 400 x 200 x 150 mm.

Mortar shall be prepared in 1:4 proportions with the addition of the minimum quantity of clean portable water for workability. Cement and sand or crushed marble mortar 1:4 mix shall be composed of one part of white cement to four part of washed white sand or crushed marble sand by volume.

Ingredients, i.e. cement and sand shall be measured in proper clean gauge boxes and the mixing shall be carried out by means of an approved mechanical batch mixer. Mortar shall be used within 30 minutes after mixing.

Horizontal and vertical joints shall be racked out 10 mm. and mortar joint thickness shall not exceed as shown in the drawing.So constructed masonry work shall be cured for at least 4 days.Block works and fair faced concrete surfaces shall be protected against damage during the progress of the works. Over the top of the capping beam, galvanized and painted steel spikes shall be provided.

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5.3 Mortar Materials for mortar, sand binding agent and water, shall be mixed by volume or by weight for at least 3 minutes with the minimum amount of water to produce correctly mixed workable consistency in a mechanical batch mixer. For small jobs, hand mixing shall be permitted, the ingredients being mixed with sufficient water to produce a correctly mixed workable mortar. Mortar shall be as strong, but no stronger than the materials it bonds together.Mortars containing plasticizers shall not be overmixed. Mixers shall be kept clean at all times. Mortar shall be used within thirty minutes after mixing. Hardened mortar shall not be used in the work and shall be removed immediately from the Site. Mortar shall be prepared in the following proportions with the addition of a minimum quantity of water for workability. The mortar for concrete block shall be as follows:

The sand for mortar shall conform to the BS 1200. The source shall be approved by the Engineer. Marine sand shall not be acceptable.

The mortar for building block walling for superstructure shall be of 1:4 mix (one part of ordinary Portland cement to four parts of sand).

The mortar for building block walling for substructure shall be of 1:3 mix (one part of sulphate resisting portland cement to three parts of sand).

Mortar, if not mixed by a mechanical mixer, shall be thoroughly mixed two times when dry and two times after adding water on a clean watertight platform. Mortar shall be mixed in small quantities and used fresh. Mortar which has begun to set or has been mixed for more than 30 minutes shall not be used or remixed.

Mortar : Batch Control (material B.S./5628 - 4551)

Measure and batch materials either by volume or weight, such that the required proportions for mortar can be accurately controlled and maintained. Measurement of sand exclusively by shovel will not be permitted.

Mix mortars with the minimum amount of water consistent with workability to provide maximum tensile bond strength within the capacity of the mortar.

Mix mortar ingredients for a minimum 3 minutes in a mechanical batch mixer. Use water clean and free of deleterious materials, which would impair the work. Do not use mortar which as begun to set, or if more than 1/2 hours has elapsed since initial mixing. Retemper mortar during 1/2 hours period as required to restore workability.

5.4 Joint Filling Sealant Movement joint filling sealants shall be of the type and colour stated on the drawings and shall be from a Manufacturer/Supplier approved by FEWA/Engineer. Two part polysulphide based sealants shall be used in strict conformity with manufacturers recommendations. Joint filler shall be a compressed sheet of wood fibre impregnated with bitumen emulsion.The filler may alternatively be a compressed sheet of cork granules bonded with bitumen or synthetic resins.Ordinary insulation board dipped in creosote will not be accepted. Premoulded closed-cell cellular rubber expansion joint-material shall comply with ASTM D1056. Premoulded closed-cell vinyl or polyvinyl chloride expansion joint material shall comply with ASTM D 1667.

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5.5 Wall Ties and Mesh Reinforcement Ties for cavity walls shall be of stainless steel to BS 1243, double triangle or twisted strip with drip.Minimum length of ties shall be 100mm in excess of the width of the cavity.Special metal ties or anchors shall be as detailed on the drawings. Every fourth layer of block work, suitable mesh reinforcement shall be provided as per standard. 5.6 Concrete Bricks Concrete bricks are manufactured by compacting the concrete under high pressure into a mould. The pressure employed shall be such that a high initial strength is achieved, enabling the brick to be removed immediately by extrusion, from the mould. The cement used shall be of ordinary or rapid-hardening Portland Cement. The aggregate shall be sand or manufactured sand. 5.7 Special Blocks and Thermal Blocks Lightweight Concrete blocks shall be manufactured using cement, lightweight aggregate and water. The lightweight aggregate shall be pulverized fly ash or volcanic aggregate obtained from an approved source. The lightweight aggregate shall comply with ASTM C 331. Thermal blocks for special purposes shall be form standard manufacturers and shall comply with the standards specified. 5.8 Pre-cast Claustra Blocks Pre-cast Claustra (Screen) Blocks shall be fabricated of white Portland cement and crushed limestone chipping in steel moulds, or of off-white terra-cotta, of the dimensions, thicknesses and patterns approved by FEWA/Engineer. The mortar for bedding, jointing and pointing of Pre-cast claustra block shall be composed of one part white cement to three parts of crushed limestone or crushed white marble.\ 5.9 Miscellaneous Materials

a) Strap and frame anchors These shall be in stainless steel to grade 304 S15 in accordance with BS EN 10095. For approved suppliers of these products refer Vendor List.

b) Reinforced galvanised steel mesh These should be hot-dip zinc coated low carbon steel to BSEN 10142 and mild steel rods complying with BS 4449, hot dip galvanised to FEWA/Engineer approval.

c) Insulation between tops of concrete block partitions and underside of structure Mineral wool or fibrous glass board of 1.1 lb density, machine cut, recessed each side of wall to accept caulking/smoke seal, placed under minimum 25% compression when installed.

14. MANUFACTURE

The standard sizes of the wall blocks shall be: - Length 400 mm, width 200 mm and height 200 mm or as shown on Approved drawings. - Any alternative measurements must be of standard ratio according to that specified in BS EN 772-2. The blocks of the load bearing walls shall not be less than 200 mm thick. - The ratio of cavitations in the hollow block shall vary between 25% to 50% and the thickness of the outer layer 35mm., the amount of the thickness shall be equal to the

size of the largest piece of aggregate used multiplied by 1.75 times, whichever of the two amounts is bigger.

- Tolerance in the given total dimensions (length or width of height shall not exceed + or -

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3 mm. at any point). a) Shrinkage

The blocks shall be tested for shrinkage according to the specifications and the results obtained must conform with the specifications in BS EN 772-2 provided the shrinkage shall not at any rate exceed 0.05%.

b) Sampling Ten blocks shall be selected at random per 1,000 blocks of each load or part thereof, or each set produced. All samples shall be clearly mark on selection in order to distinguish them from each other and so that each produced set (or part thereof) or the whole load shall be distinctly identified and distinguished.

c) Durability The concrete blocks of the load bearing walls, when tested according to BS EN 772-2, shall have an average compression strength exceeding 12.5 N/mm², provided no single result shall be less than 10 N/mm². The concrete blocks of the non-load bearing walls shall have an average compression strength of more than 7.5 N/mm², provided no single test result shall be less than 6 N/mm² minimum.

d) Durability Test The durability test under compression shall be carried out on the sample in accordance with BS EN 772-2.

e) Water Absorption Water absorption shall be 20% or less of dry weight. Blocks in contact with the ground shall be solid sulphate resisting concrete blocks coated with thick black bitumen or tar composition unless otherwise stated.

7. QUALITY ASSURANCE

7.1 Construction requirement

Before commencing masonry work, verify that Site conditions will allow construction of masonry within required limitations for wall heights, wall thickness, openings, bond, anchorage, material support, and compressive strengths of masonry units and mortars.

7.2 Mock-Up

Construct sample wall 1525 mm high and 2440 mm long of mortar and masonry units specified for project, to show colour range, texture, bond, jointing, and unit cutting to provide mock-up as specified in this section.

Approved mock-up may be included in the work.

Include in mock-up damp proof flashing, specified masonry units and accessories specified in this section.

Construct a sample wall for each type of masonry specified which is exposed to view.

7.3 Field Quality Control

Inspect and report on mortar materials and on compressive strength of mortar samples as laying of masonry progresses. Provide six 50 mm cubes of mortar from samples taken randomly at the Site, as directed.

Immediately following each inspection and/or testing submit a copy of reports to Engineer.

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7.4 Damp- Proof Course

Damp-proof course in walls shall consist of one layer of tropical quality bituminised fiber felt damp-proof course or black sheet of pitch, P.V.C. and synthetic fibers, complying with BS 743, weighing not less than 3.3 kg/m2. The damp-proof course shall be well lapped at corners and joints and bedded in cement mortar (1:4) mix and pointed both sides.

The Contractor shall also provide and build in a vertical damp proof course at jambs of openings in cavity walls and a horizontal damp proof course above such openings and to parapet walls.

Damp proof membranes to be 1000 gauge polythene sheet; joins to be lapped 150mm.

Damp proof concrete shall comprise standard structural concrete in accordance with project specification for concrete, together with suitable additives.

8. WORKMANSHIP

Samples of all types of blocks to be used shall be submitted to FEWA/Engineer for approval before any of them are delivered to the site. The approved samples shall be retained on site for use as standards until completion of the Contract.

Blocks shall not be used until one month after casting. All blocks shall be well buttered with the appropriate mortar before being laid and all hoists shall be thoroughly flushed up as the work proceeds.

Any blockwork shall be set out and built to the dimensions shown on the working drawings. All blockwork below plinth level shall be solid blockwork with blocks manufactured with sulphate resisting cement. Generally all external walls shall be cavity walls consisting of a 100 mm solid blockwork outer leaf and a 200 mm hollow blockwork inner leaf. Internal walls shall be single leaf constructed with 200 mm hollow blocks. Reinforced concrete lintels shall be provided over all openings. Weep holes shall be formed in the outer leaf of external walls immediately above the d.p.c. at plinth level and above the d.p.c. and flashings of lintels.

Walls shall be carried up regularly without leaving any part more than one meter lower than another unless the permission to do so is first obtained from the Engineer. Work which is left at different levels shall be raked back. In the case of cavity walls, both thickness shall not be carried up more than approximately 400 mm.

The courses of blockwork shall be properly levelled. The perpendicular joints shall be properly lined and quoins, jambs and other angles plumbed as the work proceeds. Reinforcement shall be included in all walls in accordance with chapters 23 and 24 of the Uniform Building Code 1979 Edition.

All walls shall be thoroughly bonded in accordance with the best constructional practice and as directed by FEWA/ Engineer.

All concrete blocks shall be soaked with water before being used and the tops of walls left off shall be wetted before work is recommenced. The faces of walls shall be kept clean and free from mortar droppings and splashes.

All blocks shall be properly spread with mortar before being laid and all joints shall be thoroughly flushed up solid through the full thickness of the wall at each course as the work proceeds.

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Walls to be left unplastered shall have a fair-face consisting of selected blocks pointed with a neat weathered or flush joint as the work proceeds, using the same mortar mix as for jointing.

Walls to be plastered shall have the horizontal joints raked out to a depth of 15 mm to form a key.

Blockwork shall be bonded to concrete columns and the like with one tie every two courses made of electro-galvanized steel ties 3 mm. thick x 10 cm. length along the column and 15 cm along the course, forming a right angle with fish-tailing at end of 15 cm. length, and fixed to column by an expansion bolt of a suitable length but not less than 4 cm. Shot bolts shall not be allowed for use.

Cavity walls shall comply with the requirements of CP 121. Cavities shall be 50 mm wide and shall include a 25 mm thick layer of insulation. The two leaves shall be bonded together with wall ties spaced 60 cm apart horizontally and approximately 400 mm apart vertically and staggered. Extra ties shall be provided at reveals, quoins and openings.

The ties shall be galvanised or stainless steel of the full-twist type. The length of the ties shall be 20 cm x 20 cm width x 3 mm thickness. The cavity shall be kept clean by lifting screeds or by other means approved by the Engineer, and shall be left clean at completion.

Allowance shall be made for temporary leaving of open courses immediately under all structural members built into the walls. These open courses shall be left in suitable positions to permit the structural members to take up their full deflection. The open courses shall be made good and pointed up after the structural members have been fully loaded and before completion of the works. An approved compressible material may be used to fill the open course.

The Contractor shall butt and fit blockwork around steel work, etc. leave or form chases for edges of concrete slabs, staircases, ends of partitions, etc. cut chases for pipes, conduits, etc. and make good.

Wooden plates and doors and window frames shall be bedded and exposed edges pointed in a sealant and fixing cramps shall be built in. Timber frames and such others abutting the wall shall be coated with bitumen or timber preservatives.

Permanent marks with levels, must be established on the building so that all elevations can be checked by means of such marks when required.

Unless otherwise started or shown on drawings, the thickness of joints shall be equal and shall be not more than 12 mm. A tolerance should be exploited so as to obtain the best appearance of the facings without the necessity of laying fragments of a block of less than 10 cm.

The erection of walls shall be in such a manner and so arranged that the workers will not stand on walls during work. For this purpose suitable scaffolding should be provided by the Contractor when walls reach heights of 1.60 meters approximately. Although all scaffolding shall be subject to the approval of the Engineer, the Contractor shall be the only person responsible for the proper erection and safety of the scaffolding.

Masonry units shall be cut with a motor driven saw designed to cut masonry with clean sharp edge.

Masonry units disturbed after laying shall be cleaned and re-laid in fresh mortar.

All block work in temporary free standing position shall be adequately braced or otherwise protected all times against the effect of lateral loading or wind pressure.

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9. REINFORCED CONCRETE BLOCK WALL STIFFENERS

Vertical stiffeners shall consist of intermediate reinforced concrete columns. The reinforcement for these stiffeners shall lap onto starter reinforcement previously cast and left protruding from the beams or slabs immediately above and below the location of the stiffener. The horizontal tie beam shall be designed at every 2.5m height of the wall.The tie column and tie beam shall constitute aframed system to resist any kind of collapse.

10. ANCILLARY WORKS

a) Doors and windows shall be built into the blockwork as the work proceeds. They shall be bedded in mortar similar to that in adjacent work. Frames shall be fixed by galvanized steel fish tail clamps at every other course or by an alternative method to be approved by FEWA/Engineer. On both vertical sides of door or window openings and over a minimum of half a block width, the blocks shall be solid or the cavities filled with concrete.

b) Blockwork built-up to structural members Unless shown otherwise on the approved drawings, the allowance shall be made for leaving, temporarily, open courses immediately under all beams and slabs. The blockwall shall no be packed up to the sofit of the beam or slab until after the full dead weight of the structure has been applied to the beam or slab.

c) Chasing Where walling is cut, holed or chased for conduits, pipes or the like, all such chases shall be filled in solid with cement mortar mix (1:4) prior to the application of the finishes. In no case shall a horizontal chase be deeper than one sixth the thickness of wall.

d) Scaffolding Scaffolding holes shall be carefully and properly filled up on completion of walling work. e) The 50mm cavity in cavity double skinned blockwall shall be filled with FEWA/Engineer approved insulation material.

11.CONSTRUCTION TOLERANCES

Variation from plumb : for vertical lines and surfaces of columns, walls and arises do not exceed 6 mm in 3 Meters or 10 mm in a storey height not exceeding 6 Meters, or 12 mm in 12 Meters or more.

For external corners, expansion joint, control joint and other conspicuous lines, not exceeding 6 mm in any storey, or 6 Meters maximum, or 12 mm in 12 Meters or more.

Variation from level: for lines of exposed lintels, sills, parapets, horizontal grooves and other conspicuous lines, not exceeding 6 mm in any bay of 6 Meters maximum, nor 18 mm in 12 Meters or more.

Variation of linear building line : for position shown in plan and related portion walls and partitions not exceeding 12 mm in any bay of 6 Meters maximum, nor 18 mm in 12 Meters or more.

Variation in cross-sectional dimensions : not exceeding minus 6 mm nor plus 12 mm.

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12. SUBMITTALS

Production data : submit manufacturer’s Specifications and other data for each type of masonry unit, accessory and other manufactured products, including certification that each type complies with specified requirements. Include instructions for handling, storage, installation and protection.

13. JOB CONDITIONS

Do not apply concentrated loads for at least 3 days after building masonry walls etc.

Protect sills, ledges and projections from dropping of mortar.

14.CURING

Factory units shall be cured in a moisture controlled atmosphere or in an autoclave at normal pressure at temperature to comply with ASTM C90, type 1.

Moisture absorption shall be limited during delivery and until time of installation to the maximum percentage specified for the average annual relative humidity.

Constructed wall surfaces shall be cured as for other concrete works for not less than 3 days. Blockwork shall be protected from hot sunlight and drying winds until mortar has sufficiently matured.

15. REPAIR, POINTING AND CLEANING

Remove and replace masonry which is loose, chipped, broken stained or otherwise damaged, or if blocks do not match adjoining blocks as intended. Provide new matching blocks and install in fresh mortar or grout, pointed to eliminate evidence of replacement.

Pointing during the tooling of joints, enlarge any voids or holes, except weep holes and completely fill with mortar. Point up all joints at corners, openings and adjacent work to provide a neat, uniform appearance, properly prepared for application of caulking or sealant compounds.

Clean exposed masonry by dry brushing at the end of each day’s work and after final pointing to remove mortar spots and droppings.

16. BUILDERS WORK

All services openings in the block walls as per the builders work drawings shall be done during the course of block work construction. The sizes and locations of openings shall be as marked in the drawings and as required by the Engineer.

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B. PLASTERING 1. GENERAL

This work consists of the supply of all plastering materials and the execution of all plastering in accordance with the Drawings and the Specifications. The work shall include all necessary labour, materials, equipment and auxiliary works as required. Plaster shall be applied in accordance with the finish schedule given on the drawings or specified elsewhere, or as directed by FEWA/ Engineer.


B.S. 12 Specification for ordinary and rapid hardening Portland cement B.S. 443 Specification for testing zinc coatings on steel wire for quality requirements B.S. 882 Specification for aggregates from natural sources for concrete B.S. 1199 Specification for building sand from natural sources B.S. 1369 Metal lathing (steel) for plastering B.S. 1494 Fixing accessories for building purposes B.S. 3148 Methods of tests for water for making concrete B.S. 4551 Methods of testing mortars and specification for mortar testing sand B.S. 4887 Mortar plasticizers B.S. 5262 Code of Practice for external rendered finishes B.S. 5492 Code of Practice for internal plastering B.S. 8000 Code of Practice for plastering and rendering Part 10

3. SAMPLES

The Contractor shall submit representative samples of the materials he proposes to use, and the Engineer shall approve the sources of such materials and shall supervise the necessary tests conducted on the representative samples in accordance with the stipulated standard tests for the respective material.

4. MATERIALS 4.1 Sand and Cement Plaster 4.1.1 Cement The materials shall be stored on Site, protected from rain, and inclement weather kept off ground and away from damp surfaces, to the satisfaction of the Engineer. Damaged or deteriorated materials shall be removed from Site.

Uniformity of the material shall be guaranteed. The cement and water shall meet the same requirements as for the Concrete Works Section of these Specifications.

4.1.2 Sand The sand to be used shall be clean, well washed and free from injurious amounts of saline, alkaline, organic or other deleterious matters, and shall be chemically and structurally stable and sieved and graded in accordance with the requirements of FEWA/ Engineer.

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The sand shall be guaranteed to produce a faultless plaster and shall comply with BS 1199 Table 1. Both the purity to the appropriate standard and the uniformity of the fractions shall be guaranteed continuously.

The sand used for the first coat shall be uniformly graded and passing through sieve No. 4 and retained on sieve No. 5. The sand used for the second coat shall be fine sand passing through sieve No. 5 (2.38 mm) and retained on sieve No. 8 (0.30 mm).

4.1.3 Water Water shall be clean, free from harmful amounts of deleterious matter and from any unusual proportion of dissolved salts. Drinking water is normally suitable.

4.1.4 Admixtures and Colouring Agents If admixtures, sealing coats and the like are used or special processes or materials applied, the maker’s or supplier’s instructions shall be strictly observed.

4.2 Job Conditions The Contractor shall protect contiguous work from soiling, spattering, moisture deterioration and other harmful effects, which might result from plastering.

5. WORKMANSHIP 5.1 General All plastering shall be executed in a neat workmanlike manner, all faces, shall be true and flat, and angles shall be straight and level or plumb and slightly rounded to a 5 mm radius or to the corner bead if required.

All tools, implements, and surfaces shall at all times be kept scrupulously clean and strict precautions shall be taken to prevent the plaster or other materials from being contaminated by pieces of partially set material which would tend to retard or to accelerate the setting time. The coating work shall not begin until all :

required openings, chases or other apertures have been cut;

pipes, fixtures, fixing pads and plugs have been fixed;

making good has been completed.

The Contractor shall protect all existing work and approaches with boards, dust sheets, etc. All droppings on to finished work shall be cleaned off immediately. Plastering shall be neatly made good up to metal or wood frames and skirting and around pipes or fittings, and the Contractor shall attend and make good after every trade. 5.2 Preparation All surfaces to be plastered shall be clean and free from dust, loose mortar and all traces of salts. Projections and concrete fins shall be hacked off. Traces of mould oil, grease, dust and other incompatible materials shall be removed by scrubbing with water containing detergent.

Where cement plaster is to be applied, the surfaces shall first be wetted and dashed with a slurry coat dashed on the surface with a steel trowel to provide a key for the first coat of plaster.The

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slurry coat shall be composed of 400 kg of cement to one cubic meter of clean coarse sand.At least a day shall elapse after the application of the slurry before the succeeding coat is started.

5.3 Plastering The sand for plastering shall be clean, fine sand and shall be chemically and structurally stable and sieved and graded in accordance with the requirements of FEWA/Engineer.

Lime shall be imported and of the hydrate type complying with Class B of BS 890.

The method of measuring and mixing plaster shall be as laid down under "Concrete Work"and the proportions and minimum thickness of finished plaster work shall be in accordance with the following:

Plaster Mix Minimum Thickness Lime, sand and cement 1 part lime two coat tota Gauged plaster Internally 2 parts cement 12 mm ceilings 10 parts sand 15 mm to walls

Cement and Sand 1 part cement two coat total Plain Face 4 parts sand 15 mm to walls

Cement and Sand 1st coat Render and Spray 1 part cement two coat, 2nd coat Finish External 4 parts sand sprayed on 13 mm overall

2nd coat 1 part cement 1 part sand

Plaster work and external cement and sand plain face rendering to a finish thickness greater than the two coat total thickness shown in the above table shall be applied using the number of coats shown on the approved drawings or in the Bill of Quantities. With regard to the lime mortars gauged with cement, the addition, just before use, of cement to small quantities of the lime/sand mix shall preferably take place in a mechanical mixer and mixing shall continue for such time as will ensure uniform distribution of materials and uniform colour and consistency. It is important to note that the quantity of water used shall be carefully controlled.

A plasticizer may be added to cement/sand plaster with the written permission.

Plaster may be mixed either in a mechanical mixing machine or by hand. Hand mixed plaster shall be first mixed in the dry state being turned over at least three times. The required amount of water should then be added and mix again turned over three times or until such time as the mass is uniform in colour and homogenous.

The plaster shall be completely used within thirty minutes of mixing and hardened plaster shall not be re-mixed but removed from the site.

Irregularities in the surfaces to be plastered shall be filled with mortar, without lime, twenty four (24) hours before plastering is commenced. Joints in blockwork etc. are to be well raked out

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before plastering to form a good key. Smooth concrete surface to be plastered shall be treated with an approved proprietry bonding agent.

All plastering shall be executed in a neat workmanlike manner. All faces except circular work shall be true and flat and angles shall be straight and level or plumb. Plastering shall be neatly made good up to wood frames and skirting and around pipes or fittings.

All angles shall be rounded to 5 mm radius.

Surfaces of undercoats shall be well scratched to provide a key for finishing coats. Screed,marks or making good on undercoats shall not show through the finishing coats. Surfaces to be trowelled smooth and shall be finished with a steel or celluloid trowel to a smooth flat surface free from trowel marks. Surfaces to be floated shall be finished with a wood or felt float to a surface free from trowel marks.

All tools, implements, vessels and surfaces shall be kept clean at all times and strictprecautions shall be taken to prevent the plaster or other materials from being contaminated by pieces of partially set material which would tend to retard or accelerate the setting time.Each coat of plaster work shall be maintained in a moist condition for at least three days after the plaster has developed enough strength not to be damaged by water.

5.3 Expanded Metal Lathing/Plaster Beads/Stops/Angles, etc.. Before plastering is commenced all junctions between differing materials shall be reinforced. This shall apply where walls join columns and beams, particularly where flush and cracks are likely to develop and as directed by FEWA/Engineer, shall be reinforced with galvanized metal lathing strips/beads/ angles/stops which shall be plugged or nailed at both edges or stapled as required with stainless steel nails at intervals not exceeding 450mm as specified hereunder.Where plaster is to be carried over a concrete column, beam or similar flush with the blockwork, expanded metal lath shall be fixed in one width right across the beam, column, etc. and shall extend 150mm on either side. 5.3.1 Plaster Stops Beads This shall be of tight-coat, galvanized steel conforming to BS 2989, and shall be fixed plumb, square and true to line and level. Metal plaster stops shall be fixed with plaster dabs. Thickness of bead shall match the plaster thickness. 5.3.2 Angle Beads Angle beads shall be tight-coat galvanized steel conforming to BS 2989, and shall be fixed plumb, square and true to line and level.Metal angle beads shall be fixed to solid backgrounds with plaster dabs. Both types of fixing shall be on each side of the angle.

5.3.3 Concrete, Blockwork and Masonry Backgrounds Concrete, blockwork and masonry backgrounds shall be drilled and plugged at not less than 40 cm centres, and the lathing shall be fixed with clout nails or wire staples driven at angle to tauten the mesh.

5.4 Internal Plaster Internal plaster shall consist of two coats (other than the slurry coat mentioned above) having a total thickness of approximately 12 m m to the following Specifications :

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The first coat shall be 8 mm thick, made with 1:3 mix (one part of cement to three parts of uniformly graded coarse sand) and shall be done between screeds not more than 2 m apart, and shall be floated and trowelled true, even and plumb, with no hollows, ridges or irregularities.This coat shall be scarred to form a key and shall be allowed to set for three days, during which period it shall be cured and kept constantly wet.

The second and final coat shall be approximately 4 mm thick and of 1:3 mix (one part of cement to three parts of fine sand) with an approved plasticizer to be used as per the manufacturers instructions, and shall have a wood or felt floated finish.

5.5 External Plaster External plaster shall consist of two coats (other than the aforementioned slurry coat) having a total thickness of approximately 20 mm, applied as follows:

The first coat shall be the same as for the first coat of internal plaster, but 14-16 mm thick.

The second and final coat shall be 6-4 mm thick and of 1:3 mix (one part of cement to three parts of fine sand), with approved plasticizer and waterproofing additive to be used in accordance with the manufacturer’s instructions.

All external plaster shall use sulphate-resisting cement.

5.6 Reveals, Jambs and Soffits The first and second coat of internal plastering to all reveals, doors and windows jambs and soffits shall be done with 1:3 mix and shall be plastered in one operation for each coat between the respective wall faces. 5.7 Rough Cast Rough-cast, where specified or asked for by the Engineer, shall be done over the final external coat of plaster and shall consist of two coats of rough-cast with 400 kgs. of white Portland cement per cubic meter of sand applied manually or by approved machine. The mix shall include quartz as instructed by the Engineer.

5.8 Mixing Material for plaster shall be measured in approved gauge boxes and shall be prepared and mixed on a watertight clean platform approved by FEWA/ Engineer. Mortar shall be mixed in quantities sufficient only for immediate use.

Plaster mix that has hardened or partially set shall not be used, revived or mixed with fresh batches. Plasticizer shall be used in accordance with the manufacturer’s instructions and to the approval of FEWA/ Engineer.

5.9 Finishes Except where otherwise specified, internal and external plastering shall be finished smooth with a wood or felt float. The finish shall be of even texture throughout, showing no joints or variations where work has been stopped and resumed. Blisters, imperfections and loose parts shall be cut out and properly made good by the Contractor.

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5.10 Curing Each coat of all plaster work and rough-cast shall be maintained in a moist condition for at least seven days after it has developed enough strength not to be damaged.

Care shall be taken to prevent too rapid drying out during hot weather and in dry winds. The Contractor shall therefore provide a protective covering of plastic or similar impervious sheeting, which shall be hung so that it is clear of the finished surface. Any cracking, discolouration or other defects caused by inadequate protection shall be remedied immediately by the Contractor.

5.11 Cutting and Patching Cut, patch, point-up and repair plasters as necessary to accommodate other work and restore cracks, dents and imperfections. Repair or replace work to eliminate blister, buckles, excessive crazing and check cracking, dry-outs, efflorescence, sweat-outs and similar defects, including areas of the work which do not comply with specified tolerances and where bond to the substrate has failed. 5.12 Cleaning and Protection

Remove temporary protection and enclosure of other work. Promptly remove plaster from doorframes, windows and other surfaces, which are not to be plastered. Repair floors, walls and other surfaces, which have been stained, marred or otherwise damaged during the plastering work. When plastering work is completed, remove unused materials, container and equipment and clean floors and plaster debris.

The Contractor shall comply with procedures required for the protection of plasters from deterioration and damage during the remainder of the construction period.

C. SCREEDS AND TOPPINGS 1. GENERAL

This Section of the Specification applies to parts of the works such as floor and roof where screeds or toppings will be used. The work shall include all necessary labour, materials, equipment and auxiliary works as required.

2. SUBMITTALS

Control samples : The Contractor shall prepare sample areas being part of the finished work for each type of screed or topping in approved locations and obtain Engineer’s approval. The size of the samples to be not less than 5 m2.

Tests : The Contractor shall carry out preliminary tests on natural aggregates in accordance with BS 812 and submit results to the Engineer for his approval.

3. MATERIALS AND PRODUCTS

Cement for screed and topping mixes is to be ordinary Portland cement to BS 12 part 2, unless otherwise specified. Screeds to ground floor slabs will contain sulphate resisting cement. The screed exposed to sun and at adverse weathering conditions shall be provided with polypropelyne fibre. Air entraining agent for lightweight roof screeds shall be to ASTM C796-77.

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Admixtures : do not use admixtures other than plasticizers and water-retaining agents without prior approval. Do not use admixtures of any type with proprietary mixes. Do not use calcium chloride or any admixtures containing calcium chloride.

Water : to be clean, free from silt, organic matter, alkali, salts and other deleterious impurities. Obtain approval of source of supply. Test to BS 3148. Cement-sand screed: fine aggregate : to BS 882, grading limit C or M mix proportions : 1 - 3 parts cement-sand.

Lightweight roof screed : composed of one part cement, three parts fine aggregate to BS 882 grading limit C or M and air entraining agent to produce lightweight concrete density 800 kg/m3 and compressive strength 6 kg/m2.Multilayer or self levelling epoxy screed with average thickness of 5 mm over suitable primer. Slip-Resistant Material : Silicon carbide or aluminium oxide, graded between BS 410 sieves 1.70 mm and 500 micrometers.Liquid surface hardener and dustproofer : silicofluoride based liquid.

4 WORKMANSHIP 4.1 General The Contractor shall take adequate precautions to protect the work carried out from premature drying out by hot weather. He shall protect and keep clean all completed areas. Any droppings shall be cleaned off immediately. The Contractor shall take adequate precautions to prevent damage to screeds. Defective work shall be made good before the finishes are applied. Before any screeding is carried out the Contractor shall prepare and clean the bases thoroughly to remove concrete mortar, plaster, dirt, rust and grease.

Surface laitance to the base slab shall be brushed off with a stiff broom before it has hardened and at a later date the surface shall be thoroughly cleaned by scrubbing and washing. The base slab shall be kept wetted for several hours before the screed is laid. The excess water shall be removed and cement slurry of creamy consistency shall, then, be brushed in. Alternatively, the surface can be primed and a bonding agent applied in accordance with the manufacturer’s recommendations. The screed or topping shall be laid while the slurry or bonding agent is still wet.

4.2 Mixing The materials shall be mixed thoroughly to a uniform consistency. The water content of mixes is to be the minimum necessary to achieve full compaction, low enough to prevent excessive mortar being brought to surface during compaction. The mixed material shall be used while sufficiently plastic to enable proper compaction.

The mixing of the materials shall be carried out only in quantity for the work immediately in hand. The material which has stiffened by starting to set shall not be used.

4.3 Joints The joints, where not shown on the drawings shall be agreed with the Engineer before starting the work. The forms are to be square edged with steel top surface and securely fixed. Compaction at

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the edges shall be properly carried out to give a level and closely abutted joints with no lipping.The bay sizes for bonded toppings are to be not more than 15 m2, ratio of length to breadth being not more than 3/2 and a joint occurring over every joint in base slab. For unbonded toppings the bay sizes shall be not more than 10 m2, ratio of length to breadth being not more than 3/2.

Unless otherwise specified, the screeds shall be cast continuously as far as possible without joints using ‘wet screeds’ between strips or bays wherever practicable.

4.4 Compaction Lightweight roof screed shall be laid in one layer from low to high points and compacted in accordance with air entertaining agent manufacturer’s instructions to achieve the specified density and apply 1-2 cement-sand slurry to produce smooth finish.

4.5 Tolerances Tolerances for floors : sudden irregularities shall not be permitted. Gradual irregularities expressed as maximum permissible deviation shall be : 3 m straight edge : ± 3 mm 1 m straight edge : ± 1 mm Tolerances for roof screeds : sudden irregularities shall not be permitted. Maximum permissible deviation under a 2 m straight edge is to be ± 3 mm.

4.6 Finishes Smooth floated finish : The Contractor shall use a hand float, skip float or power float to give an even surface with no ridges or steps on screeds to receive rigid tiles and the like.Toppings or roof screeds shall be finished with a float to an even surface with no ridges or steps. Hand or power trowel shall be used successively at intervals, applying sufficient pressure to the surface to give a uniform smooth finish free from trowel marks and other blemishes. Where slip resistant trowelled finish is required the topping shall be floated with a hand or power trowel successively at intervals to give a smooth finish from trowel marks. While the topping is still plastic slip resistant material shall be sprinkled evenly at the rate of 1 kg/m2 and trowelled into surface.

Where a surface hardener is used the Contractor shall clean the surfaces properly and apply the number of coats of liquid surface hardener in accordance with manufacturer’s recommendations. Immediately after laying the screeds or toppings the surfaces shall be protected from wind, draughts and strong sunlight. As soon as the setting has taken place cover closely with polythene sheeting and keep it in position for not less than 7 days.

Documents

Federal Electricity & Water Authority Water Directorate ... · PDF file5.1 Concrete Blocks 5.2 Calcium Silicate Block ... DUBAI Order: Document: MWA_PRO ... Premoulded closed-cell