03-division 3-section 03300 cast in place concrete-version 1.0

ABU DHABI SEWERAGE SERVICES COMPANY

(ADSSC)

GENERAL SPECIFICATION FOR CIVIL WORKS

DIVISION 3 CONCRETE

SECTION 03300 CAST IN-PLACE CONCRETE

ADSSC/GSCW Division 03 Section 03300

Cast in Place Concrete Rev: 01 April 2008 of 41

General Specification for Civil Works Abu Dhabi Sewerage Services Company

(ADSSC)

DOCUMENT CONTROL SHEET

Revision No. Date Revision Description / Purpose of Issue

01 April 2008 First Issue.

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TABLE OF CONTENTS

1 GENERAL ..........................................................................................................4 1.1 SCOPE ...................................................................................................4 1.2 RELATED DOCUMENTS .......................................................................4 1.3 STANDARDS..........................................................................................4 1.4 SUBMITTALS .........................................................................................7 1.4.1 PRODUCTS AND MATERIALS APPROVAL. ........................................7 1.4.3 DRAWINGS ............................................................................................9 1.5 QUALITY CONTROL............................................................................10 1.6 DELIVERY, STORAGE AND HANDLING ............................................11 1.6.1 CEMENT, GGBS, PFA AND SILICA FUME. ........................................11 1.6.2 AGGREGATES.....................................................................................11 1.6.3 ADMIXTURES ......................................................................................12 1.6.4 WATER.................................................................................................12

2 PRODUCTS......................................................................................................12 2.1 CONCRETE MIX ..................................................................................12 2.2 PORTLAND CEMENT ..........................................................................15 2.3 GROUND GRANULATED BLASTFURNACE SLAG (GGBS). .............16 2.4 PULVERIZED FLY ASHES (PFA) ........................................................17 2.5 SILICA FUME (SF) ...............................................................................18 2.6 AGGREGATES.....................................................................................19 2.7 ADMIXTURES. .....................................................................................21 2.8 WATER.................................................................................................21 2.9 FIBER REINFORCEMENT...................................................................22 2.10 HESSIAN/POLYTHENE SHEETING/CURING COMPOUND ..............22 2.11 VAPOUR BARRIER..............................................................................23

3 EXECUTION.....................................................................................................23 3.1 PRELIMINARY MIX TESTS .................................................................23 3.2 CONCRETE TRIAL MIX AND PLACEMENT........................................23 3.3 BATCHING AND MIXING OF READY MIXED CONCRETE................25 3.4 ROUTINE CONCRETE TESTING........................................................28 3.5 DELIVERY OF CONCRETE.................................................................31 3.6 PREPARATION FOR CONCRETING ..................................................32 3.7 PLACEMENT OF CONCRETE.............................................................34 3.8 ADVERSE WEATHER CONCRETING.................................................35 3.9 COMPACTION OF CONCRETE ..........................................................36 3.10 FINISHING CONCRETE ......................................................................37 3.11 CURING AND PROTECTION...............................................................38 3.12 SCHEDULE OF TOLERANCES...........................................................39 3.13 REPAIR AND PATCHING ....................................................................39 3.14 DEFECTIVE CONCRETE ....................................................................40 3.15 LOADING OF STRUCTURES ..............................................................40




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1 GENERAL

1.1 SCOPE

This section of the specification gives the requirements for concrete batching, delivery, placing, compacting, finishing and curing.

1.2 RELATED DOCUMENTS

The following sections of the specification shall be read in conjunction with this section.

Section 01000-07 Submittals Section 01000-08 Quality control Section 01000-09 Materials and equipment Section 03100 Concrete formwork Section 03200 Concrete reinforcement Section 03700 Joints in concrete

1.3 STANDARDS

All activities relating to this section of the specification shall comply with the following or approved equal standards.

Cement BS EN 197-1 Cement. Composition, specifications and conformity criteria

for common cements. BS 4027 Specification for sulfate-resisting Portland cement. BS 4550-0 Methods of testing cement. General introduction. BS 4550-3.1 Methods of testing cement. Physical tests. Introduction. BS 4550-3.4 Methods of testing cement. Physical tests. Strength tests. BS 4550-3.8 Methods of testing cement. Physical tests. Test for heat of

hydration. BS 4550-6 Methods of testing cement. Standard sand for mortar

cubes. Ground Granulated Blast Furnace Slag (GGBS) BS 6699 Specification for ground granulated blastfurnace slag for

use with Portland cement. Pulverized Fuel Ash (PFA) BS 3892-1 Pulverized-fuel ash. Specification for pulverized- fuel ash

for use with Portland cement BS EN 450 Fly ash for concrete. Definition, requirements and quality

control Silica Fume ASTM C1240 Standard Specification for Silica Fume Used in

Cementitious Mixtures




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Aggregates ASTM C88 Standard test method for soundness of aggregates by use

of sodium sulfate or magnesium sulfate. ASTM C123 Standard test method for lightweight particles in aggregate. ASTM C127 Standard test method for density, relative density (specific

gravity) and absorption of coarse aggregate. ASTM C128 Standard test method for density, relative density (specific

gravity) and absorption of fine aggregate. ASTM C131 Standard test method for resistance to degradation of small

size coarse aggregate by abrasion and impact in the Los Angeles machine.

ASTM C142 Standard test method for clay lumps and friable particles in aggregates.

ASTM C227 Standard test method for Test for potential alkali reactivity of cement-aggregate combinations. (mortar bar method)

ASTM C289 Standard test method for potential alkali-silica reactivity of aggregates. (chemical method)

ASTM C1260 Standard test method for potential alkali reactivity of aggregates. (mortar-bar method)

BS 812-105.1 Testing aggregates. Methods for determination of particle shape. Flakiness index.

BS 812-105.2 Testing aggregates. Methods for determination of particle shape. Elongation index of coarse aggregate.

BS 812-109 Testing aggregates. Methods for determination of moisture content.

BS 812-112 Testing aggregates. Method for determination of aggregate impact value.

BS EN 933-1 Tests for geometrical properties of aggregates. Determination of particle size distribution. Sieving method.

BS EN 933-2 Tests for geometrical properties of aggregates. Determination of particle size distribution. Test sieves, nominal size of apertures.

BS EN 933-7 Tests for geometrical properties of aggregates. Determination of shell content. Percentage of shells in coarse aggregates.

BS EN 1367-4 Tests for thermal and weathering properties of aggregates. Determination of drying shrinkage.

BS EN 1744-1 Tests for chemical properties of aggregates. Chemical analysis.

BS EN 12620 Aggregates for concrete.

Concrete admixtures BS EN 480-1 Admixtures for concrete, mortar and grout. Test methods.

Reference concrete and reference mortar for testing. BS EN 480-2 Admixtures for concrete mortar and grout. Test methods.

Determination of setting time.




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BS EN 480-4 Admixtures for concrete mortar and grout. Test methods. Determination of bleeding of concrete.

BS EN 480-5 Admixtures for concrete mortar and grout. Test methods. Determination of capillary absorption.

BS EN 480-6 Admixtures for concrete mortar and grout. Test methods. Infrared analysis.

BS EN 480-8 Admixtures for concrete, mortar and grout. Test methods. Determination of the conventional dry material content.

BS EN 480-10 Admixtures for concrete, mortar and grout. Test methods. Determination of water soluble chloride content.

BS EN 480 11 Admixtures for concrete, mortar and grout. Test methods. Determination of air void characteristics in hardened concrete.

BS EN 480-12 Admixtures for concrete, mortar and grout. Test methods. Determination of the alkali content of admixtures.

Water ASTM D512 Standard test methods for chloride ion in water. ASTM D513 Standard test methods for total and dissolved carbon

dioxide in water. ASTM D516 Standard test method for sulfate in water. BS 3148 Methods of test for water for making concrete. Concrete ACI 305R Hot weather concreting ASTM C138 Standard test method for density (unit weight), yield and air

content (gravimetric) of concrete. ASTM C173 Standard test method for air content of freshly mixed

concrete by the volumetric method. ASTM C231 Standard test method for air content of freshly mixed

concrete by the pressure method. ASTM C232 Standard test methods for bleeding of concrete. ASTM C497M Standard test methods for concrete pipe, manhole sections,

or tile. (Metric version) ASTM C1064 Standard test method for temperature of freshly mixed

hydraulic-cement concrete. ASTM C1202 Standard test method for electrical indication of concrete’s

ability to resist chloride ion penetration.. BS 1881-124 Testing concrete. Method for analysis of hardened

concrete. BS EN 206-1 Concrete. Specification, performance, production and

conformity BS EN 12350-2 Testing fresh concrete. Slump test. BS EN 12350-6 Testing fresh concrete. Density. BS EN 12390-2 Testing hardened concrete. Making and curing specimens

for strength tests BS EN 12390-3 Testing hardened concrete. Compressive strength of test

specimens




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BS EN 12309-7 Testing hardened concrete. Density of hardened concrete BS EN 12390-8 Testing hardened concrete. Depth of penetration of water

under pressure. BS EN 12504-1 Testing concrete in structures. Cored specimens. Taking,

examining and testing in compression. Curing compounds ASTM C309 Standard specification for liquid membrane forming

compounds for curing concrete. General ISO 9000 Quality management systems.

1.4 SUBMITTALS

1.4.1 PRODUCTS AND MATERIALS APPROVAL.

In order to verify compliance with the specification the Contractor shall submit information for all products and materials used in the Works to the Engineer for approval sufficiently in advance of their use in accordance with the Contract programme allowing ample time for review, trials, testing, approval and ordering times. Submittals related to this section will only be approved by the Engineer if the results of the concrete trial mix and placement conducted in accordance with Clause 3.02 are to his satisfaction. In certain circumstances this trial mix and placement requirement may be waived at the Engineers discretion. Reference shall also be made to Section 01000-09 of the specification on products and materials approval. Information to be submitted shall comprise but not necessarily be limited to:

a) Details of the proposed ready mix supplier which shall include at least

the following:

i. Name and location of supplier and his plant. ii. Management structure at plant. iii. Description of production, and quality control management practice. iv. Description of plant, equipment and production rate per hour. v. Description of maintenance management practice. vi. Identify technical team, their qualifications and experience. vii. Number of delivery vehicles and their rated capacities. viii. Description of in-plant testing facilities.

b) Mix design for each grade of concrete to be used to include at least the

following:

i. List of all materials to be used in the mix, cement, ground granulated blast furnace slag (GGBS), pulverized fly ashes (PFA), silica fumes, fiber reinforcement, aggregates, admixtures and water etc, their sources and type, trade names, detailed recent test reports and manufacturer’s certificates confirming compliance with the specified requirements and referenced standards.




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ii. For admixtures the following specific information shall also be given.

The generic chemical names of the main active ingredients in the admixture.

Chloride and alkali content. Range of solids content. Reducing sugar content by percentage weight of the assupplied

admixture which shall be less than 4% and be confirmed with a test certificate.

All information as required under BS EN 480-1, 2, 4, 5, 6, 8, 10, 11, 12

Dosage limits at 25oC and 30oC Any detrimental effects, short or long term, that may affect the

performance or durability of the concrete.

iii. Cement content. iv. GGBS content if applicable. v. PFA content if applicable vi. SF content if applicable. vii. Fibre reinforcement content if applicable. viii. Maximum aggregate size. ix. Aggregate grading curves. x. Proportionate quantities of all individual materials on a yield of 1m3.

Aggregate proportions shall be based on measured and not relative densities.

xi. Details of calculations for various ratios to include water cement ratio, fine to coarse aggregate ratio, paste to aggregate ratio by volume, fineness modulus.

xii. Compressive strength at 7 and 28 days. xiii. Hardened density. xiv. Water permeability. xv. Water absorption. xvi. ASTM C1202 permeability at 7 and 28 days. xvii. Sulphate and chloride contents. xviii. Concrete setting time and bleed. xix. Target slump at discharge and slump retention time. xx. Target unit weight. xxi. Target temperature. xxii. Names, locations and services to be provided by sub-contractors

regarding testing, supplies technical support and know how to be used in concrete production and placement.




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1.4.2 METHOD STATEMENTS The Contractor shall submit method statements to the Engineer for approval 4 weeks in advance of commencing the site activity in accordance with Section 01000-07 of the specification. These shall comprise but not necessarily be limited to:

a) Details for receiving, pumping, placing, compacting, sampling and curing

concrete. Include at least the following: i. Identify concrete crew, their skills, experience and training received. ii. Identify all equipment and materials that will be required on site

before any concreting operation commences and the method of utilising equipment, materials and men to ensure that the concreting operation runs smoothly, without errors and in a timely fashion.

iii. For each structure identify concrete placement sequences which shall include:

Timing of pour during hot weather conditions. Estimated time for pours. Concrete required per hour. Numbers of vibrators required Concrete final finish. Method of curing Quality control measures.

iv. The arrangement for sampling, making of cubes, curing, transport

and testing of cubes.

b) Repair of deficiencies which may occur during construction which shall include blow holes, lack of cover, honeycombing, plastic cracking, other types of cracks and tie rod holes.

1.4.3 DRAWINGS

a) The Contractor shall submit drawings to the Engineer for approval in advance of commencing the site activity in accordance with Section 01000-07 of the specification. These shall comprise but not necessarily be limited to:

i. Layout of concrete pours including position of all vertical and

horizontal joints, height of lifts, size of pours, rate of pours, pump locations and truck access routes.




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b) Representative samples, as agreed with the Engineer, must be

submitted for at least the following items at the same time as the particulars are submitted. All samples shall be taken in the presence of the Engineer’s representative.

i. Cement, GGBS, PFA and SF.

Provide cement, GGBS, PFA and SF samples as requested by

the Engineer for testing.

ii. Aggregates.

Provide samples of both fine and coarse aggregates for testing at least 3 weeks prior to beginning deliveries to the site and at regular intervals as requested by the Engineer.

iii. Admixtures.

As requested by the Engineer.

iv. Water.

Provide samples of water proposed for concreting and curing

works for testing.

v. Fibre reinforcement.

Small bag of fibre reinforcement. 1.5 QUALITY CONTROL

a) Prior to dispatch of any product and/or material from source the contractor shall notify the Engineer in writing in sufficient time to allow the Engineer the opportunity to inspect and test the product and/or material prior to delivery in accordance with Section 01000-08 of the specification.

b) Products and materials shall be from a manufacturer/supplier who

operates a quality system which is registered to ISO 9000 series or approved equal.

c) To allow the Engineer to inspect the Works the Contractor shall give the

Engineer a minimum of 24 hours notice of carrying out the following activities on site.

i. Delivery and placement of concrete.




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1.6 DELIVERY, STORAGE AND HANDLING

Delivery, storage and handling of products and materials shall be in accordance with the manufacturers recommendations, Section 01000-09 of the specification and the following provisions.

1.6.1 CEMENT, GGBS, PFA AND SILICA FUME.

a) Store and protect cement from deterioration and contamination. b) Store in dust controlled dry waterproofed silos either shaded or painted

white.

c) Provide separate cement silos for each type of cement. Do not mix different types of cement.

d) Any consignment of cement not used within 3 months from the date of

manufacture which in the opinion of the Engineer is of doubtful quality shall not be used in the Works.

e) Provide copy of plant certificate and delivery note of every delivery to

batching plant.

f) Cement delivered to the work site in drums or bags provided by the manufacturer or supplier shall be stored in the drums or bags until used in the Works, in clearly marked separate storage facilities and be used in the order in which they are received.

g) GGBS, PFA and silica fume shall be stored in separate clearly identified

facilities as for the requirements for cement. 1.6.2 AGGREGATES.

a) Store in purpose built shaded or covered bins or bunkers with an impermeable sloping substrate.

b) Prevent intermixing from adjacent aggregate piles of a different size by

the provision of adequate walls between bins.

c) Prevent contamination of aggregates.

d) Provide suitable labels for each bin/bunker.

e) Height of stock pile within each bin shall not exceed 3m.

f) Cooling of aggregates by spraying with water shall not be accepted.




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g) Washed fine aggregate shall be drained overnight from the time of delivery.

1.6.3 ADMIXTURES

a) Store in waterproofed shaded closed container, clearly marked for easy identification of its contents and fitted with a stirrer or circulating pump.

b) Each type of admixture shall have its own circulation system.

1.6.4 WATER

a) Water shall be stored in clean covered tanks to prevent contamination.

b) The chilled storage water tank shall be insulated. 2 PRODUCTS

2.1 CONCRETE MIX

a) Concrete shall comply with the requirements of Table 1 and Table 2 below unless otherwise approved by the Engineer.




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Table 2.1.1 - Grades of Concrete

Concrete Grade

Nominal Max Size of

Aggregate mm

Min Cement Content kg/m3

Type of Cement

Max Water/ Cement

Ratio

28 day Min Compressive

Strength N/mm2

C20 20 250 SRPC 0.60 20

C40/10 10 400 OPC 0.40 40

C40/20 20 350 OPC 0.42 40

C40FR 20 350 SRPC/OPC 0.40 40

Notes to Table 2.1.1 1. Where adequate workability is difficult to obtain at the maximum water/cement

ratio allowed, the use of plasticisers or water-reducing admixtures shall be considered.

2. Cement contents in excess of 400kg/m3 shall not be used. 3. Grade C20 concrete shall typically be used for infilling of soft areas, blinding,

pipe support and surround. 4. Grade C40/20 concrete shall typically be used for precast work, slabs, walls,

columns, beams, chambers and reinforced structures. 5. Grade C40/10 concrete shall be used in congested areas at the discretion of the

Engineer. 6. Grade C40FR shall include up to 1.0kg/m3 of fibre reinforcement with exact

quantities being determined by site trials. 7. GGBS, PFA and silica fumes may be proposed by the Contractor as cement

substitutes up to agreed limits all to the approval of the Engineer.




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Table 2.1.2 - General Requirements for Concrete

Test Test Method Specification Limit

Temperature at placement ASTM C1064 30°C Max

Slump at placement BS EN 12350-2 125 ± 25mm

Unit weight ASTM C138 BS EN

12350-6 ± 35kg/m3 from Target Unit Weight

Bleeding ASTM C232 1.0% Max

Hardened density BS EN 12390-7 Not Applicable

Compressive strength BS EN 12390-3 See Table 1

Water permeability of concrete at 28 days old BS EN 12390-8 25mm Max

Chloride ion penetration ASTM C1202 ≤4000 coulombs for mixes without mineral additives

Water absorption after 30 mins of concrete at ASTM C497 2.3% Max 28 days old

Chlorides by weight of cement for reinforced BS 1881 Part 124 concrete only Manufactured using OPC 0.30% Max Manufactured using SRPC 0.15% Max

Sulphates by weight of cement for all concrete

BS 1881 Part 124 4.0% Max

Notes to Table 2.1.2 1. For concrete Grade C20 only slump at placement and compressive strength

tests shall apply. 2. Target unit weight shall be established during plant trials.




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b) Design of Concrete Mixes.

i. At the commencement of the Works the Contractor shall design a mix for each grade of concrete listed in Table 1 that is required to be built into the works.

2.2 PORTLAND CEMENT

a) Portland cement shall comply with CEM 1 42.5 N to BS EN 197 for Ordinary Portland Cement (OPC) and Class 42,5H (LH) to BS4027 for Sulphate Resisting Portland Cement (SRPC) except as modified by the specification herein.

i. The Contractor shall provide details of other cements if specified or

recommended. ii. High Alumina cement shall not be used under any circumstances

for structural concrete or for corrosion protection of steel or concrete.

iii. Cement batch certificate shall meet the following requirement.

Attribute or Property Unit OPC SRPC 1. Chemical assay C3A % 5 - 9 < 3.5 Insoluble residues % max 1.50 Loss on ignition % max 3.00 Acid soluble alkalis % max 0.60 MgO % max 5.00 SO3 % max 2.50 Cl % max 0.10




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2. Acceptance tests Specific surface area (Blaine)

m2/kg 225 - 325

Initial setting time minutes - ≥ 60 Final setting time minutes ≤ 600 - Compressive strength 2 days

N/mm2 - ≥ 10

Compressive strength 28 days

N/mm2 42.5 – 62.5

Le Chatelier soundness

mm ≤10

b) The cement producer shall have tested every batch of cement to the

relevant standard and shall provide a test certificate not older than 2 months that contains the above information and in addition the following data for every batch of cement delivered.

i. Chemical essay

Calculated phase composition (C3A, C4AF, C3S, C2S) Free lime content Carbon content

ii. Acceptance tests

Initial and final setting time Heat of hydration value

c) Any cement which is, in the opinion of the Engineer, unsuitable for use in

the Works shall be rejected and the Contractor shall promptly remove such cement from the Site at his own cost and consequences.

d) Whenever required by the Engineer, representative samples of cement

shall be taken and forwarded in the presence of the Engineer to an approved independent laboratory for analysis to check the compliance against the Specification.

i. A representative sample of cement shall be collected by the

Contractor from each consignment and kept in the store. Samples shall be disposed only with permission of the Engineer.

2.3 GROUND GRANULATED BLASTFURNACE SLAG (GGBS).

a) GGBS shall comply with BS 6699, in addition to the following requirements, unless otherwise approved by the Engineer.

i. Raw material (slag) is limited to one source. Slag supplied or

blended from several different plants or mills shall not be accepted. ii. The GGBS must originate from an iron winning process using the

balst furnace process and the hot slag must be rapidly water




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quenched before extraction as slag suitable for use as a concrete improver additive.

iii. GGBS quality (i.e. reactivity) is subject to considerable variation from the different sources using the same process. Therefore the supplier must have a long term contract from the same furnace to ensure consistency of performance. The supplier shall provide documentary evidence to validate the fact..

iv. One of the important markers for quality is the composition, glass content and fineness. The supplier’s test certificate shall include the the items in the test certificate:

Particles > 45 microns : 20% max Glass content : 90% min

v. GGBS that has been manufactured earlier than one year shall not

be used. vi. Blast furnace slag which has been used for de-sulphurising iron

shall not be used for producing GGBS vii. GGBS shall be supplied to the concrete batching plant in bulk

powder form.

Interground slag cement shall not be used. Preblended slag cements shall not be used.

viii. Whenever required by the Engineer, representative samples of

GGBS shall be drawn and forwarded in the presence of the Engineer to an approved independent laboratory for analysis to check compliance against the Specification.

A representative sample of GGBS shall be collected from each

consignment and kept in the store. Samples shall be disposed only with the permission of the Engineer

2.4 PULVERIZED FLY ASHES (PFA)

a) PFA shall comply with BS 3892-1 and BS EN 450, in addition to the following requirements, unless otherwise approved by the Engineer.

b) PFA shall be limited to one source. PFA blended from several different

sources shall not be accepted.

c) Whenever required by the Engineer representative samples of PFA shall be taken and forwarded in the presence of the Engineer to an approved independent laboratory for analysis to check compliance against the specification.




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2.5 SILICA FUME (SF)

a) Silica fume shall comply with ASTM C1240 inclusive of the options indicated in the standard and in addition to the following requirements unless otherwise approved by the Engineer.

i. The silica fume must originate from ferrosilicon or silicon smelters.

Fume from other base metal furnaces shall not be acceptable ii. The silica fume producer shall produce a type test certificate for

each furnace of the fume’s origin in compliance with ASTM C 1240 and include all the optional requirements stipulated in the standard.

iii. Silica fume shall be from one source, such evidence shall be provided on demand. Silica fume supplied or blended from several different sources shall not be accepted.

iv. Silica fume shall be supplied in powder form and comply with the following specification limits:

SiO2 content : 85% min Cl content : 0.02% max Free carbon : 3% max Loss on ignition : 4% max Bulk density : 600 kg/m3 max Specific surface area : (BET) 16,000 m2/kg min. Si metal content : 0.1% max

b) Batch test certificates issued by the producer of the silica fume shall accompany every batch delivered and contain at least the following details:

i. The type and location of of the furnace e.g. ferrossilican, El Ismaere,

Bavaria ii. Relevant dates, signatures, official seal. iii. The test results iv. A declaration confirming that the silica fume originated at the

named furnace v. Batch test certificate shall be issued by the producer.

c) Whenever required by the Engineer, representative samples of silica

fume shall be drawn and forwarded in the presence of Engineer to an approved independent laboratory for analysis to check compliance against the specification at the Contractor’s expense.




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2.6 AGGREGATES.

a) Fine and coarse aggregates shall be in accordance with Table 2.6.1 below along with the following general requirements unless otherwise approved by the Engineer:

i. Aggregates shall consist of hard, durable, uncoated materials

containing no harmful substances in quantities sufficient to adversely affect the strength or durability of the concrete or attack the reinforcement.

ii. Aggregates shall not have the potential to cause alkali-silicate or

alkali-carbonate reactions or other damaging chemical reactions between aggregates and alkalis. The Contractor shall carry out tests to ensure that the aggregate-cement-additive mixture is free of potentially damaging reactions.

iii. Aggregates shall be initially assessed for reactivity in accordance

with ASTM C289 and C1260 and if potential activity is shown, then tests in accordance with ASTM C227 shall be conducted.

iv. Aggregates used in the permanent work shall be obtained only from

the sources approved by the Engineer.

v. Aggregates shall comply with the requirements of BS 882 except as modified in this section of the specification and if necessary shall be mechanically sieved or washed clean with potable water to comply with these requirements.

vi. Fine aggregate shall be naturally occurring uncrushed sand,

crushed quarried sand or a blend of the two. The use of clean dune sand blended with coarser sand may be permitted if it meets the applicable specification requirements.

vii. Coarse aggregates shall be crushed quarried stone.




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Table 2.6.1 - Aggregate Tests

Requirement Test Method Fine Coarse Min Test Aggregate Aggregate Frequency Limit Limit Grading BS EN 933-1

BS EN 933-2 BS 882 BS 882 Once a day

Material finer than 0.075mm: • Natural, uncrushed/crushed • Crushed rock

BS EN 933-1 BS EN 933-2

3% Max 9% Max

1% Max 1% Max

Once a day

Clay lumps and friable particles

ASTM C142 1% Max 1% Max As requested

Light weight pieces ASTM C123 0.5% Max 0.5% Max As requested

Water absorption ASTM C127 ASTM C128

2.3% Max 2% Max Once a week

Specific gravity apparent ASTM C127 2.6 Min 2.6 Min Once a month ASTM C128 Shell content in aggregates: BS EN 933-7 Once every 3 •Coarser than 10mm None 5% Max months •5mm to 10mm None 15% Max •2.36mm to 5mm 10% Max None •Finer than 2.36mm None None • Hollow shells None None Particle shape: • Flakiness index • Elongation index

BS 812-105.1 BS 812-105.2

25% Max 30% Max

Once every week

Acid soluble chlorides: BS EN 1744-1 Once every 3 •For OPC reinforced 0.03% Max 0.02% Max months •For SRPC reinforced 0.03% Max 0.01% Max •For OPC unreinforced 0.05% Max 0.04% Max •For SRPC unreinforced 0.03% Max 0.02% Max Acid soluble sulphates BS EN 1744-1 0.3% Max 0.3% Max Once every 3

months Soundness: • MgSO4 (5 cycles) or • Na2SO4

ASTM C88 12% Max 10% Max

12% Max 10% Max

Once every 3 months

Mechanical strength: • Impact value • Los Angeles abrasion

BS 812-112 ASTM C131

30% Max 30% Max

Once every 3 months

Drying shrinkage BS EN 1367-4 0.05% Max 0.05% Max Once every 6 months




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Potential reactivity: Once every 6 • Aggregates, chemical ASTM C289 Innocuous Innocuous months method • Cement-aggregate combination

ASTM C227/C1260

6 month expansion

6 month expansion

0.10% Max 0.10% Max Moisture content BS 812-109 Twice a day 2.7 ADMIXTURES.

a) Water reducing and retarding admixtures shall be to BS EN 480.

i. Admixtures containing chlorides shall not be used. ii. Use water reducing admixtures and retarding admixtures in

accordance with the manufacturer's recommendations. iii. Notify the Engineer of the limits of dosage for the various

temperatures encountered during use. iv. Retarding admixtures shall not contain reducing sugars of more

than 4% by weight of the admixture. 2.8 WATER

a) Water used for concrete mixes, washing of equipment and curing shall be potable water and shall comply with the requirements of BS 3148 and Table 4 below.

b) pH of water used in concrete works shall be in the range of 6 to 9.

c) Ice if used, shall be flaked and shall be the product of frozen water which

complies with the acceptance criteria of BS 3148 and Table 2.8.1.

d) Every effort should be made to protect water pipes and tanks from the sun by burying, shading, insulating or painting white.

e) Whenever required to do so by the Engineer, the Contractor shall take

samples of the water being used and test it for quality.

f) No source of water shall be used unless approved by the Engineer.




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Table 2.8.1 - Water Quality

Maximum Concentration Test Method Specification Limit

Chlorides ASTM D512 250 mg/l

Sulphates ASTM D516 350 mg/l

Alkali carbonates and bicarbonates

ASTM D513 500 mg/l

2.9 FIBER REINFORCEMENT

a) Fiber reinforcement shall comply with the following requirements unless otherwise approved by the Engineer:

i. Materials shall be polypropylene with a nominal surface area of

225m2/kg, a nominal thickness of 18 microns and a nominal length of 12mm.

ii. Exact dosage for the fiber reinforcing shall be determined during plant trial but shall be within manufacturer’s recommended limits

iii. Fiber shall be supplied in cellulose concrete ready bags to ensure rapid dispersion during mixing. For uniform distribution, the fibers shall be added at the batching plant.

2.10 HESSIAN/POLYTHENE SHEETING/CURING COMPOUND

a) Hessian used for curing shall be close knit and new and shall be approved by the Engineer.

b) Polythene sheeting to be used for curing shall have a minimum

thickness of 100 microns and a minimum reflectance of 70% and be undamaged.

c) Water for curing purposes shall be potable and shall comply with the

requirements of BS 3148.

d) Curing compounds shall be to ASTM C309, Type 1, Class B with a curing efficiency of greater than 80%, a water retention of less than 0.55kg/m2 and a touch drying time of a maximum of 4 hours. They shall be compatible with subsequently applied finishings or coverings and shall be not deleterious to bond of cementitious materials to concrete.




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2.11 VAPOUR BARRIER

Vapour barrier shall be a clear polythene sheet with a minimum thickness of 250 microns.

3 EXECUTION

3.1 PRELIMINARY MIX TESTS

a) Preliminary mix tests shall be carried out with the approved materials to demonstrate that the mixes for each grade of concrete will satisfy the specification.

i. Samples shall be taken and tests shall be conducted at a laboratory

approved by the Engineer to demonstrate conformance with all the requirements given in Tables 2.1.1 and 2.1.2.

ii. If any of the values obtained are unacceptable, the mixes shall be redesigned.

3.2 CONCRETE TRIAL MIX AND PLACEMENT

a) Unless otherwise approved by the Engineer concrete will not be allowed to be placed in the works until a successful combined trial mix and placement has been conducted to the satisfaction of the Engineer.

b) Prior to the combined trial mix and placement the Contractor shall satisfy

himself by inspection and audit that the ready mix plant and concrete placement crew are capable, ready, well equipped and experienced to conduct the successful production and placement of concrete.

c) A trial mix and placement shall be conducted to test and prove the ability

of the contractor to obtain concrete of the desired quality and his ability to place, compact and cure the concrete to achieve the desired properties of strength, durability, finish and workmanship.

d) The trial mix and placement shall be conducted in the same manner that

a normal placement into the works would be executed.

e) At least 1m3 of concrete for each grade proposed for use shall be manufactured, sampled, tested, delivered, pumped, placed, compacted and cured into a dummy construction at the site following the details, methods and plans submitted under clause 1.04 above.

i. For concrete grade C40 at least one reinforced horizontal slab

measuring 1.2m X 1.2m X 0.30m thickness and one reinforced wall section measuring 1.6m high X 1.6m long X 0.30m thickness, reinforced as directed by the Engineer, shall be constructed as trial panels.




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f) The dummy construction shall be designed:

i. For coring samples at 7 and 28 days for compressive strength and density testing and chloride ion penetration and chloride and sulphate profiling.

ii. As a surface for trial and demonstration of application of coatings, laminates and other treatments or finishings to be used in the Works.

g) Fresh concrete shall be sampled and tested for concrete bleed, slump,

temperature, unit weight and air content and at least 19 number 150mm cubes shall be moulded and cured for testing at 7 and 28 days to the schedule given in Table 3.2.1 below. Methods of making and curing cubes shall be in accordance with BS EN 12390-9

Table 3.2.1 Concrete Trial Mix Cube Testing

No. of Cubes To be Tested for Test Method

3 7 day cube compressive strength and density

BS EN 12390-3 BS EN 12390-7

3 28 day cube compressive strength and density

BS EN 12390-3 BS EN 12390-7

3 7 day 100mm core compressive strength

BS EN 12504-1

3 28 day 100mm core compressive strength

BS EN 12504-1

1 7 day chloride ion penetration and chloride and sulphate profile

ASTM C1202 BS 1881-124


ASTM C1202 BS 1881-124

3 28 day water penetration BS EN 12390-8

1 28 day 75mm core water penetration BS EN 12390-8

1 Spare

h) At 5 days and 25 days 100mm cores shall be extracted from the dummy

placement and shall be tested at 7 and 28 days to the schedule given in Table 3.2.2 below.




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Table 3.2.2 - Concrete Trial Mix Core Testing

No. of Cores To be Tested for Test Method

3 7 day compressive strength and density

BS EN 12504-1

3 28 day compressive strength and density

BS EN 12504-1


ASTM C1202 BS 1881-124


ASTM C1202 BS 1881-124

3 28 day water penetration BS EN 12390-8

Notes to Table 3.2.2 1. An acid soluble chloride and total sulphate content shall be performed on the

sample before the ASTM C1202 test is carried out. 2. An acid soluble chloride and total sulphate profile shall be made on the entire

thickness of the disc after the ASTM C1202 test by analysing 10mm depth dust drillings extracted within 4 hours of testing to prevent drying out/migration.

i) The results of the tests undertaken in Clauses 3.2g) and 3.2h) shall meet

the requirements of Tables 2.1.1 and 2.1.2.

j) Whenever a change of brand or source of supply for any of the concrete constituents occurs, additional trials directed at the Engineers discretion may be required to demonstrate compliance with the specification.

3.3 BATCHING AND MIXING OF READY MIXED CONCRETE

a) Concrete shall be batched, mixed and delivered in accordance with BS EN 206-1, unless otherwise approved by the Engineer.

b) Provide concrete to a mix design approved at the trial mix and

placement and to possess the minimum properties determined at the trial mix placement. None of the properties shall be below minimum or above the max values, specified in Tables 2.1.1 and 2.1.2.




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c) Weights and volumes of all constituent materials must take account of the free water already contained in the material. Adjust actual weights or volumes accordingly. Water in admixture shall be calculated as part of the free water.

d) All raw materials shall be added to the mixer by an automated computer

controlled system. Manual or semi-manual additions shall not be carried out without the prior approval of the Engineer.

e) The mixer shall not retain significant amounts of concrete upon

discharge. Mixer shall be washed and cleaned at frequent intervals and before the making of different mix designs.

f) Unless otherwise approved by the proposed ready-mix plant must be an

offsite commercial plant properly staffed and equipped to consistently produce the classes of concrete to be used at the works to the standards achieved and agreed upon at the trial mix and placement.

g) Concrete for the works must be batched in a modern fully automated

computerised wet batching plant.

h) Batching plant shall be calibrated in-house every three months and at least once a year by an independent agency approved by the Engineer. Batching plant accuracy shall be as shown in Table 3.3.1 below.




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Table 3.3.1 - Batching Tolerances

Constituent Material Individual Batch % Cumulative Load %

Coarse aggregate (20mm) ± 2 ± 1

Coarse aggregate (10mm) ± 2 ± 1

Fine aggregate (5mm) ± 2 ± 1

Dune sand ± 2 ± 1

Cement ± 2 ± 1

GGBS ± 2 ± 1

PFA ± 2 ± 1

Silica fume ± 4 ± 1

Water ± 1 ± 1

Ice ± 1 ± 1

Liquid admixture(s) ± 3 ± 3

i) A batch-system computer printed batch ticket must accompany each

load delivered to site and shall include at least the following.

i. Batch ticket number, date and vehicle number. ii. Identification of supplier and batching plant. iii. Name of purchaser and destination site. iv. Project designation/contract number. v. Grade of concrete, targeted strength and targeted free W/C ratio. vi. Itemised list of raw materials, their sources, type, trade names and

weights or volumes used in each batch and their variances. vii. Mixing time. viii. Number of batches in the load. ix. Weight and volume of concrete delivered. x. Time of batching. xi. Space for signatures of batch plant representative and contractor’s

representative.

j) The readymix plant shall have a flaked ice maker or other approved source of ice.

k) The readymix plant must be equipped with a water chiller of sufficient capacity capable of maintaining the water temperature in the water storage tank to below 6oC during hot weather.




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l) The ready-mix plant must be operated by well trained qualified personnel.

m) A sufficient number of well maintained concrete agitator trucks shall be

provided to maintain a continuous delivery of the required amount of concrete to the job site without delay or hindrance.

n) A fully equipped testing laboratory operated by experienced and

qualified personnel must exist at the production plant to carry out the tests on materials and fresh and hardened concrete as specified herein.

o) The plant must have the capability to stock sufficient raw materials to

meet the peak demands of concrete supply to the works.

p) A second supplier that meets all the requirements must be proposed in the event that the primary supplier becomes incapacitated.

q) Unless approved by the Engineer delivery agitator trucks shall not carry

separately any liquid admixtures when delivering concrete to the site.

r) Unless approved by the Engineer water, liquid admixture or other additives shall not be added to the concrete after wet concrete has been loaded into agitator trucks.

s) Dry concrete ingredients shall not be loaded into the truck at any time.

3.4 ROUTINE CONCRETE TESTING

a) The Contractor shall perform the tests given in Table 3.4.1 below at the frequency stated to ensure that the concrete delivered to the project is in conformance to the approved mix design.




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Table 3.4.1 - Routine Concrete Testing

Test Class C20 Concrete Class C40 Concrete Test Method Test Frequency Test Frequency

Fresh concrete

Temperature Not applicable Every load ASTM C1064 BS 5328-4

Concrete slump Every alternative Every load ASTM C143 load BS EN 12350-2

Concrete unit weight During trial mixes and as requested by the Engineer

During trial mixes and as requested by the Engineer

ASTM C138 BS EN 12350-6

Air content Not applicable During trial mixes ASTM C173 and as requested by ASTM C231 the Engineer

Identification of aggregates

Every load Every load By washing

Concrete bleeding Not applicable During trial mixes and once a month

ASTM C232

Hardened concrete Density All cubes required

for All cubes required for

BS EN 12390-7

compressive compressive strength strength Compressive strength

Min of one set for every 100m3 cumulative of concrete

Min of one set per casting per day and for every 50 m3

cumulative of Concrete

BS EN 12390-3

Concrete cores from structure

Not applicable As requested by the Engineer

BS EN 12504-1

Non destructive Testing

Not applicable As requested by the Engineer

Resistance to chloride ion penetration

Not applicable One test for every 50m3 cumulative of concrete or as requested by the Engineer

ASTM C1202




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Water permeability Not applicable One test for every 100m3 cumulative of concrete or as requested by the Engineer

BS EN 12390-8

Water absorption Not applicable One test for every 100m3 cumulative of concrete or as requested by the Engineer

ASTM C497M

b) 150mm concrete cubes for compressive strength testing shall be taken

in sets of six at such times and places as the Engineer may direct unless otherwise stated and in any case not less than the rate specified in Table 8. Acquire concrete for these cubes at the point of delivery and from the same load and prepare in accordance with BS EN 12390-2.

i. Cube moulds of the same type and manufacture shall be used for

making all test specimens. ii. All cubes shall be kept in insulated boxes until demoulded. iii. All cubes shall be demoulded between 16 and 24 hours after

casting and immediately placed in curing tank. iv. All demoulded cubes from site shall be transported to an approved

testing laboratory under the supervision of the Engineer. v. Cubes shall be numbered consecutively throughout the work and

marked with the date of casting. vi. Test three cubes at 7 days and another three at 28 days for

compressive strength and density. vii. If a cube fails to produce the minimum specified strength or density

when tested at 7 days the Contractor shall immediately remove the structure of which the cube represents or await at his own risk the result of the 28 days test.

viii. If the 28 days results also fail to attain the average strength specified.

The Contractor at his own expense may opt to test cores from

the structure of which the cubes represent. The strength data from the cores shall be in line with the data obtained during the trial mix and placement.

The Contractor shall remove the structure of which the cubes and cores represent or execute such additional works or adopt such additional measures as the Engineer may direct at the Contractor’s expense.

ix. If the chloride ion penetration of the 28 day cube, with no mineral additives in the mix, exceeds 4000 coulombs the contractor shall immediately remove the structure if the Engineer so directs.




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c) In certain cases the Engineer may so direct or the Contractor may with

the prior approval of the Engineer obtain approved samples of the concrete from the structure by drilling or coring and after dressing the samples for testing, submit the samples to density, compressive, permeability (ASTM C1202) water cement ratio, cement content, additive content, excess voids and petrographic tests in order to obtain further information. Correlation data between cube and cylinder strengths shall be extracted from the trial and placement results and such data shall be used in ascertaining or obtaining validity of results between placed concrete and cube samples. Should the Engineer refuse to sanction the coring of cured structures the Contractor shall not make any claim in consequence thereof. Samples dressed for testing shall not contain any reinforcement other than minor reinforcement in the plane parallel to the compressive faces. All costs caused by investigation of concrete quality shall be borne by the Contractor.

d) Submit to the Engineer a copy of records for each sample cube taken

and tested.

e) The Contractor shall submit for the Engineer’s approval suitable repair materials for repairing cored areas and for making good minor defects in concrete.

f) Provide and maintain the following equipment on site for the Engineer's

use during the contract.

1 No. Set of sieves to BS EN 933-2. 36 No. (min) 150mm moulds for test cubes and accessories. 2 No. Cones for slump tests and accessories. 1 No. Electronic balance reading to 20kg (sensitivity 1gm) 1 No. Cover meter (for measuring cover depth). 3 No. Lab grade glass thermometer 0-70 (or 100)oC. 2 No. Tape measures (readability 1mm). 1 No. Humidity meter. 1 No. Portable anemometer. 1 No. Wet dry thermometer. 1 No. Maximum and minimum thermometer.

g) The Contractor shall record wet and dry bulb temperatures, wind velocity

and any precipitation three times daily. (0800, 1200 and 1500 hours) 3.5 DELIVERY OF CONCRETE

a) Transportation, delivery and handling shall be in accordance with BS 5328 unless otherwise approved by the Engineer.

i. Contractor is to check all delivery tickets and batch print out sheets

and confirm the compliance of the batch to the specification to the




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satisfaction of the engineer before concrete is allowed to be poured. ii. Concrete shall be conveyed from the mixer to its place in the works

as rapidly as possible by methods which will minimise segregation and drying out.

iii. Ensure that concrete is of the required workability at the point and time of placing.

iv. If segregation has nevertheless occurred in any instance, the materials shall be remixed to the satisfaction of the Engineer or discarded.

v. The drum of the agitator shall be rotated for at least 2 minutes at the mixing speed before discharging concrete from the agitator.

vi. Contractor shall be responsible for delivering concrete in such a manner as to avoid cold joints.

vii. Rate of sampling and testing shall be as defined in Table 8. viii. If field tests show excessive temperature, non-compliant slump, unit

weight or invalid aggregates, the entire batch of concrete from which the sample in question was taken will be rejected.

3.6 PREPARATION FOR CONCRETING

a) Formwork and accessories shall be in accordance with the requirements of Section 03100 of the standard specification.

b) Reinforcement shall be in accordance with the requirements of Section

03200 of the standard specification.

c) Construction joints.

i. Form construction joints as required in slabs and beams at the quarter point of the span and at right angles to the member except where otherwise approved by the Engineer. Where slabs are supported by beams, construct both beams and slabs in one operation.

ii. In all cases, provide vertical stop boards at the end of each section of work which is to be concreted in one operation. Thoroughly compact concrete against these stop boards.

iii. Construct wall panels consecutively. Where this is not possible, form a gap not exceeding 1m between adjacent panels. Do not concrete the gap until a minimum interval of 7 days has expired since the casting of the most recent adjacent panel.

iv. The size of bays for reinforced floors, walls and roofs shall not exceed 7.5m in either direction and 6m when unreinforced or nominally reinforced.

v. Provide construction joints of plain butt type or rebated type as directed or approved by the Engineer.

vi. If the Contractor’s methods of forming construction joints are not proving effective the Engineer shall order the Contractor to execute at the Contractor’s expense such preventative measures as the Engineer may consider necessary to ensure the watertightness of




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the joints. vii. In water retaining structures all construction joints shall require the

use of an approved type of water stop or water bar. viii. Construction joints shall be so located as not to impair the strength

of the structure and be in accordance with the requirements of Section 03700 of the specification.

ix. Concrete which forms the face of a construction joint shall have all laitance removed and the aggregate exposed prior to placing of fresh concrete.

Laitance shall wherever practicable be removed by spraying the

concrete surface with water under pressure and brushing it whilst it is still green.

Laitance may also be removed by the application of surface mortar retarder followed by washing and scrubbing with stiff broom.

Where the laitance cannot be removed whilst the concrete is still green, the whole of the concrete surface forming part of the joint shall have the aggregate exposed by means of a proprietary power driven scabbling/brush hammer as approved by the Engineer.

All loose matter shall be removed and the exposed surface thoroughly cleaned by wire brushing, air blasting or washing until the surface to which fresh concrete is applied is clean and saturated with suitable water.

If in the opinion of the Engineer any deleterious materials have come in contact with the concrete at the construction joint, the concrete shall be cut back to such a depth as the Engineer shall order and the required surface shall be thoroughly cleaned with compressed air and water jet or other approved means and brushed and watered immediately before depositing fresh concrete.

d) Movement joints.

i. Construct movement joints for expansion and contraction joints in

accordance with the details and to the dimensions shown on the drawings or where otherwise ordered by the Engineer and in accordance with the requirements of Section 03700 of the specification

e) In locations where new concrete is doweled to existing work, drill holes

in existing concrete, insert steel dowels and secure with approved chemical grouts.

f) Co-ordinate the placement of joint devices together with the erection of

concrete formwork and placement of form accessories.




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3.7 PLACEMENT OF CONCRETE

a) Place a concrete grade C20 blinding layer of a minimum thickness of 75 mm, immediately upon completion of any excavation and where shown on the drawings or ordered by the Engineer, to prevent deterioration of the formation and to form a clean working surface for the structure.

b) Install vapour barrier comprising two layers of 250microns thickness

polythene sheet to underside of blinding concrete and ground slabs on grade. Lap joints by a minimum of 100mm and do not disturb barrier during concreting operations.

c) Provide Engineer with a minimum of 24 hours prior notice of the

commencement of operations to enable appropriate inspections to be carried out. If concrete is not placed within 24 hours of the approval being given, make a fresh application for approval for concreting. Perform further inspections immediately prior to concreting to check that placement areas and surfaces are clean, formwork and reinforcement workmanship and formations are in compliance, all necessary equipment, tools and curing materials are at the placement area, staff have been properly trained and instructed.

d) Ensure reinforcement, inserts, embedded parts, formed expansion and

contraction joints, water stops and water bars cannot be disturbed during concrete placement.

e) Ensure that the concrete is not more than 30oC immediately prior to

placement and compaction. If during any part of the compaction the unplaced concrete temperature rises above 30oC, further placement shall be halted, unless otherwise approved by the Engineer.

f) Do not mix or place concrete when ambient temperature is above 40oC

on a rising thermometer or 43oC on a falling thermometer.

g) Slabs requiring surface finishing must be poured in late afternoon or evening during falling temperatures unless otherwise agreed with the Engineer.

h) Only the previously nominated approved and trained crew shall conduct

the placement in accordance with the approved submittals on plan, methods and manner of placement.

i) If concrete in any part of the placement begins to set before the entire

placement has been completed, all placing operations shall halt immediately; the ends of the placement shall be suitably trimmed and stopped and curing shall be applied.




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j) Pour and compact concrete in horizontal layers not exceeding 0.5m and

keep it at an even level throughout the Work. Do not allow concrete to slide or flow down sloping surfaces directly into its final position. Place concrete to its final position using previously approved means. Avoid separation of the constituent materials.

k) Ensure that vibration shock or other disturbances are not transferred to

the reinforcement, formwork and compacted concrete.

l) Do not allow the concrete to be dropped freely from a height greater than 1.5m. Use chutes, or conveyor belts designed to ensure there is no segregation or loss of mortar.

m) The following shall not occur - runs, honeycombing, segregation, voids

and grout/matrix loss.

n) Maintain records of concrete placement. Record date, location, quantity, air temperature, test samples taken and any problems encountered.

o) Place the concrete continuously between the control joints and

construction joints. When placing concrete against horizontal or inclined elements of waterstops, lift the waterstop and place concrete and compact it to a level slightly higher than the underside of the waterstop before releasing the waterstop to ensure complete compaction of the concrete around the waterstop.

p) Concreting shall be carried out continuously up to the construction joints.

The timetable for the depositing of concrete shall be so arranged that no face of concrete shall be left for more than 20 minutes before fresh concrete is placed against it. Do not permit cold joints to occur.

q) Place floor slabs in checkerboard or saw cut pattern as indicated.

r) Saw cut joints within 12 hours after placing. Use 5mm thick blade and

cut into 1/4 depth of slab thickness. 3.8 ADVERSE WEATHER CONCRETING

a) ACI 305 guidelines shall be used

b) Do not mix or place concrete when ambient temperature is above 40oC on a rising thermometer or 43oC on a falling thermometer.

c) Slabs requiring surface finishing must be poured in late afternoon or

evening during falling temperatures unless otherwise agreed with the Engineer.




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d) Do not mix or execute concrete work during the hours of 0900 to 1500

during the months May to September, unless otherwise agreed with the Engineer.

e) Do not execute concreting if it rains or during sandstorms.

3.9 COMPACTION OF CONCRETE

a) Except for slabs less than 100mm thick, all concrete cast in place shall be compacted with power driven internal type vibrators at a frequency of not less than 6,000 cycles per minute, supplemented by hand spading and tamping unless otherwise approved by the Engineer.

i. Unless otherwise agreed by the Engineer, slabs less than 100mm

thick shall be compacted by approved vibrating screeds. ii. The type of vibrators shall be subject to approval of the Engineer.

b) Internal type vibrators shall be inserted into the uncompacted concrete

vertically and at regular intervals.

i. Vibrators shall not come into contact with the reinforcement or the formwork. When fusion bonded epoxy coated reinforcement is present the vibrators shall be equipped with rubber or non metallic vibrating heads.

ii. Internal type vibrators shall not be placed in the concrete in a haphazard manner nor shall concrete be moved from one part of the work to another by means of the vibrators.

iii. Vibrators shall at all times be adequate in numbers, amplitude and power to compact the concrete properly and quickly throughout the whole of the volume being compacted to the satisfaction of the Engineer.

iv. Spare vibrators shall be readily on hand in case of breakdown.

c) Compaction shall commence as soon as there is sufficient concrete to immerse the vibrator and shall continue during the placing operations so that at no times shall there be a large volume of uncompacted concrete in the formwork.

d) Duration of vibration shall be limited to that required to produce

satisfactory compaction without causing segregation.

i. Vibration shall not be continued after water or excess grout has appeared on the surface.

e) External vibrators.

i. External vibrators shall be rigidly clamped to the formwork resting




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on an elastic support so that both the form and the concrete are vibrated.

ii. The formwork shall be strong and tight to prevent distortion and leakage of grout.

iii. Concrete shall be placed in thin layers and the position of the vibrator may have to be changed as concreting progresses.

iv. If approved by the Engineer portable non clamped vibrators may be used at sections not otherwise accessible.

v. The frequency of the vibrator shall have at least 8,000 cycles per minute unless otherwise approved by the Engineer.

f) Concrete shall be compacted to the levels desired. Compacted concrete

shall not be moved or displaced. In the event compacted concrete is moved, the disturbed concrete shall be recompacted if the slump is greater than 75 mm, otherwise the Engineer shall direct that the concrete be removed from site.

3.10 FINISHING CONCRETE

a) Requirements for formed surfaces shall comply with the requirements of Section 03100 of the specification.

b) Unformed finishes shall be as designated on the drawings and shall

comply with one of the following:

i. Class U1 finish.

Class U1 shall be used at construction joints only. Concrete shall be levelled and screeded, to form a uniform plain

or ridged finish, which shall not be disturbed in any way after the initial set.

Surplus concrete shall be struck off immediately after compaction.

Class U1 is the first stage for Class U2 and U3 finishes and for a bonded concrete surface.

ii. Class U2 finish.

Shall be a wood float finish applied to slab surfaces which are to receive trowel and other finishes such as screeds, floor finishes and coatings.

Floating shall be done after the initial set of the concrete has taken place and the surface has hardened sufficiently.

Concrete shall be worked no more than is necessary to produce a uniform surface free from screed marks.

iii. Class U3 finish.

Shall be a hard smooth steel-trowelled finish applied to slab




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surfaces that are exposed to view or are to be covered with thin film coating systems..

Trowelling shall not commence until the moisture film has disappeared and the concrete has hardened sufficiently to prevent excess laitance from being worked into the surface.

Surface shall be trowelled under firm pressure and left free from trowel marks.

iv. Bonded finish.

Where a bonded concrete surface is specified, the laitance shall be removed from the Class U1 finished surface and the aggregate exposed while the concrete is still green.

v. Broomed finish.

Where a broom finish is specified, the surface of the concrete shall first be levelled and screeded and then brushed in one direction with a stiff broom.

3.11 CURING AND PROTECTION

a) Immediately after placement, protect concrete from evaporative losses and damage as follows:

i. Immediately after finishing, the concrete shall be protected by

placing overlapped polythene sheets for the first 24 hours. Overlapping shall be at least 150 mm.

ii. The polythene sheets shall be kept in contact or near contact with the surface of the concrete and prevented from displacement by wind, foot traffic or other disturbances.

iii. After the lapse of the first 24 hours, remove the polythene sheet. Overlapped hessian that has been prewetted shall be placed in direct contact with the surface of the concrete. The hessian shall be overlapped by at least 150mm.

iv. Cover the wet hessian immediately with polythene sheet overlapped by at least 150mm. The overlapped edges of the polythene shall not be coincident with the overlapped edges of the hessian underneath it.

v. Secure the polythene and wet hessian against displacement by wind, foot traffic or other disturbances.

vi. The concrete surface shall be kept wet or at 100% relative humidity continuously for a period of at least 7 days.

vii. The curing system shall be monitored and managed. Corrections and adjustments shall be made if necessary by a nominated staff member approved by the Engineer.

viii. For walls and free standing columns after removal of the formwork the polythene and wet hessian subsequently shall be wrapped helically and secured by tying tightly against the column.




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ix. Exposed free ends containing protecting reinforcements shall be protected and kept wet by stuffing with crumpled strips of wet hessian and polythene into the spaces in between the protruding reinforcements. .

x. Where pipes and cavities enter the structure the open areas of the pipes shall be stopped with loose stuffing and the free openings taped up with polythene to prevent moisture loss from the concrete surface into such cavities.

xi. Chemical curing membranes shall not be used unless the geometry is of such a nature that there is no alternative upon which it shall be used with the prior approval of the Engineer. If curing membranes are used, at least three of four coats shall be applied depending on the nature and characteristics of the proprietary material.

xii. Maintain records of curing operations and inspections. 3.12 SCHEDULE OF TOLERANCES

a) Concrete work shall be constructed to tolerances which shall permit the proper assembly of components and subsequent installations.

b) Tolerances shall be compatible with the designated finish.

c) Accuracy of the work shall be within the following tolerances, unless

otherwise shown on the drawings or unless otherwise approved by the Engineer.

i. All laying out dimensions ± 5mm ii. Sections of concrete members ± 5mm iii. Surface of foundations against ground ± 10mm iv. Top surfaces of foundations, bases and piers ± 20mm v. Surface level of floor slabs (5m straight edge) ± 5mm vi. Surface level of floor slabs to datum ± 10mm vii. Verticality of columns and walls per storey height ± 5mm viii. Surface levels of plinths to datum ± 3mm

3.13 REPAIR AND PATCHING

a) The Engineer shall inspect the concrete immediately upon removal of forms.

b) Patch imperfections as directed.

c) Plastering of defective concrete using cement plaster as a means of

making good will not be permitted, except in the case of minor surface porosity when the Engineer may approve a surface treatment by running in cement and sand mortar of the same richness as the concrete. The method and materials to be used shall require the prior approval of the Engineer.




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d) Do not treat any concrete surfaces until the Engineer has inspected the structure.

e) Holes formed in concrete surfaces by formwork supports or the like shall

be filled neatly with non shrink mortar as approved by the Engineer. 3.14 DEFECTIVE CONCRETE

a) Defective Concrete shall be defined as one or more of the following:

i. Not conforming to required levels, lines, details and elevations. ii. Failure to attain the required concrete strength, permeability or

finish. iii. Non conforming due to improper placement or voids, preparation of

concrete formwork, insufficient cover, improper formwork joints, honeycombing, segregation, excessive voids, damage surface, exposed reinforcement, improperly placed snap on or cone ties, unsatisfactory surface for the performance of finishing work on the concrete.

b) The discovery of defective concrete must be reported to the Engineer,

immediately. Remedial work shall not be carried out without the prior agreement of the Engineer. A proposal to the method, nature and materials to be used in the repair of defective concrete shall be submitted to the Engineer. The Engineer has the right to instruct the removal of the structure in part or whole if he deems that the structure is irreparable or the proposed repair is not consistent with restoring the fitness of the structure.

c) The Engineer’s decision shall be final in all aspects related to the repair

or demolition of defective concrete structures. 3.15 LOADING OF STRUCTURES

a) Do not apply load of any kind to any part of a concrete structure until the concrete has matured for at least 7 days and then only with the approval of the Engineer and after confirmation that the specified 7 day cube strengths have been met.

b) Do not apply the full design load until a period of 28 days has elapsed

c) Do not permit backfilling around any structure incorporating a ground or

floor slab before that slab has been cast and properly cured for a period of 28 days and fully protected or until the design strength has been reached.

d) The structure shall not be subjected to any flooding, hydrostatic pressure

or contamination until the concrete has been fully protected in accordance with the specification.




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END OF SECTION



03-division 3-section 03300 cast in place concrete-version 1.0

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