Abu Dhabi, United Arab Emirates. STANDARD CONSTRUCTION SPECIFICATIONS (PART 1 - ROADS, Second Edition 2020)

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4.3.12.8

Rejecting Fresh Concrete

Prior to sampling, the Engineer may reject any batch or load of concrete that appears defective in
composition without testing. This includes cement content or aggregate proportions. Rejected
material shall not be incorporated in the structure.

4.3.12.9

Concrete with Nonconforming Strength

Concrete with tested compressive strengths (refer to Section 4.3.12) that fail to meet acceptance
level requirements will be rejected. Rejected concrete and the associated work shall be removed
and replaced at the Contractors expense. Removal and replacement limits will be evaluated and
approved by the Engineer prior to start of the Contractor’s removal work.

4.3.13

Curing Materials

All concrete curing compounds and concrete evaporation retardants must demonstrate conformance
to the requirements of these Standard Specifications. Each lot of the material shall be sampled at
the site of the works and tested for acceptance.

Material that fails to meet the requirements of these Standard Specifications shall not be used.

4.3.13.1

Sheet Materials for Curing Concrete

Sheet materials for curing concrete shall meet the requirements of ASTM C171, “Sheet Materials for
Curing Concrete,” except that only the white, reflective type shall be used.

4.3.13.2

Liquid Membrane-forming Concrete Curing Compounds

Liquid membrane-forming compounds used for curing concrete shall conform to ASTM C309, Type
1D or 2, Class A or B, requirements; except that the loss of water within 72 hours shall not exceed
0.40 kg/m

for all applications, per ASTM C156.

4.3.13.3

Burlap Cloth

Burlap cloth shall meet the requirements of AASHTO M 182, Class 4.

4.3.13.4

Sampling

A product sample shall be submitted for each material under consideration, with the request for
approval of material. Sample sizes shall be per the applicable testing standard as described in the
subsections of Section 4.3.13, specifically:

•

Sheet materials: ASTM C171

•

Liquid membrane-forming compounds: ASTM C309

•

Burlap cloth: AASHTO M 182

Sample containers for liquid membrane-forming concrete curing compound shall be standard friction
seal 500 ml cans, lined to prevent rusting. Cans for sampling at the manufacturing site shall be
provided by the manufacturer.

Sampling of liquid membrane-forming concrete curing compound shall comply with the following
procedures, as applicable:

For production sampling, the following should occur:

1. Select 3 samples during actual transfer, or filling, operations to the shipping containers.

2. Take the first sample from the fill stream after 15 %, but before 30 %, of material has been

transferred or filled. Label the sample No. 1 and indicate the approximate number of drums
filled.

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3. Take the second sample from the fill stream after 40 %, but before 60 %, of material has been

transferred or filled. Label the sample No. 2 and indicate the approximate number of drums
filled.

4. Take the third sample from the fill stream after 70 %, but before 90 %, of material has been

transferred or filled. Label the sample No. 3 and indicate the approximate number of drums
filled.

For sampling drums, the following should occur:

a. Select three drums, at random, for each identifiable lot or batch.

b. Thoroughly disperse material in each drum with a mechanical mixer.

c. Check each drum for complete dispersion by scraping a 25 mm by 25 mm slat, or similar object,

along the drum bottom.

1. Remove the slat and examine the end for settlement and material along the length for

uniform appearance.

d. Secure a sample, using a 25 mm diameter tube or pipe, for each of the three drums.

1. Insert the tube or pipe to within approximately 150 mm of the bottom of the drum, place the

palm of the hand over the open end of the tube or pipe to form a seal and withdraw the tube
over the sample can and discharge sufficient material to fill the can.

2. Discharge the remainder of material back into the drum.

e. Allow material in the tube to drain down to a drip and wipe material from the exterior of the

tube before sampling another drum.

When drums cannot be identified by lot or batch, segregate into groups of no more than 20 drums
each. Assign a lot or batch number to each group and sample according to the drum sampling
procedure. If there are 3 drums or less, sample each drum.

For bulk storage sampling, the following should occur:

a. Bulk storage tanks must be designed for recirculation; therefore, have fixed stirrers or use

portable stirrers to insure complete mixing prior to discharge or use of material.

b. Ensure complete mixing as described in Step 3 of the drum sampling procedure, prior to

sampling.

c. Bulk storage tanks with re-circulating systems may be sampled from a re-circulating line or

from the discharge line. Discharge approximately 19 l into a clean container before securing
sample.

1. Circulate for 3 to 5 minutes, discharge approximately 19 l and secure a second sample.

Repeat the circulation and discharge. Secure a third sample. Number the samples in the
order taken.

2. Discharged material may be returned to the storage tank if clean containers have been

used.

d. Bulk storage tanks using mixers may be sampled in the same manner as drums, using a tube.

1. Secure three samples: 1 from the top third of the tank, 1 from the middle third, and 1 from

the bottom third.

Under no conditions shall two or more portions of material be blended or mixed to form a composite
sample.

Samples of liquid membrane-forming compounds for curing concrete must be labelled with the batch
number; the part of the batch represented, i.e., the first, middle, or last third; the total batch quantity
represented; and the producer, material type, date of sampling, date of manufacture, and sampler's
name.

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Cost of sampling, testing, and processing shall be borne by the Contractor.

4.3.13.5

Tests and Acceptance

Material shall be accepted based on the Engineer

’s approval of a request for approval of materials,

which shall include the following information:

1. Company name

2. Physical and mailing addresses

3. Type of material

4. Laboratory test report for each material with test data showing compliance with these standard

specifications

5. Contact person and telephone number

4.3.14

Steel Reinforcing Bar

Concrete reinforcement shall meet the requirements of Chapter 5.

4.3.15

Joint Sealing Materials

Use of joint fillers, pads, waterstops, proprietary or custom-built expansion-joint assemblies, or other
incidental materials used in forming, constructing, and sealing permanent joints, shall be subject to
the approval of the Engineer. Joint filler and sealants shall conform to drawing requirements. When
not specified, one of the joint fillers identified in these specifications may be used.

Samples for each lot taken by, or in the presence of, the Engineer shall be submitted by the
Contractor to the Engineer for approval. Samples must be submitted for testing 14 days prior to use
in the works.

Each lot of the joint filler or sealant shall be identified with the batch and lot number, material, the
batch quantity, the date and time of manufacture, and the name and address of the manufacturer;
and shall be accompanied by the manufacturer's certification attesting compliance with this
specification.

When required by the Engineer, the Contractor shall submit test certificates issued by

an approved, independent testing authority to confirm that the respective materials comply with the
specified requirements, or a certificate by the patent holder or designer certifying that the
manufactured item complies in all respects with relevant product specifications.

4.3.15.1

Fixed-joint Seal

Joint sealer shall repel the intrusion of stones, dirt, and other material into the joint or into the material
itself. Joint sealer shall be neoprene, preformed or extruded type, of the size and shape indicated
on the Contract plans. Preformed joint sealer material shall comply with the requirements of
AASHTO M 220 or ASTM D2628. Lubricant adhesive, for use with the preformed sealer, shall
conform to ASTM D4070.

Shape, width, and depth of the sealer shall meet the following requirements:

1. Such that it is compressed to the point of being substantially solid with a minimum of air spaces

when installed at the minimum joint opening.

2. Such that the top centre of the exposed surface is depressed below the surface of the sealer

edges when compressed.

3. Approved by the Engineer prior to being furnished.

Sealer  shall  be  flexible  and  pliable  and  retain  its  elasticity  at temperatures  from  -28°  C  to  54°  C.
Sealer  shall  not  develop  appreciable  permanent  set  after  full  compression  of  the  approved  joint
shape for the full effective life of the material. It shall be compatible with the material of which the
joint  surfaces  are  composed  and  be  relatively  unaffected  by  the  normal  moisture  in  the  material.
Joint sealer shall not be field spliced, except when specifically permitted by the Engineer.

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Each lot of the adhesive shall be delivered in containers plainly marked with the manufacturer's
certification attesting compliance with this specification.

4.3.15.2

Preformed Joint Fillers

Preformed joint fillers shall be furnished in a single piece for the depth and width required for the
joint with a thickness not less than 13 mm.

Table 4-28: Joint fillers

Type

Specification

Preformed expansion joint filler

(bituminous type)

AASHTO M 33 or

ASTM D1751

Preformed sponge-rubber and cork expansion joint fillers

AASHTO M 153*

Type I

–

sponge-rubber

Type II

–

cork

Type III

–

self-expanding cork

Preformed expansion joint fillers

(nonextruding and resilient bituminous types)

AASHTO M 213

Flexible cellular joint filler

ASTM D1056, Type 2,

Grade 4 or 5

*Compression test specimen shall recover to at least 65 % of its thickness before testing. Compressive
strength shall be at least 0.07 MPa.

4.3.15.3

Backer Rod

Backer rod, or backing material, shall conform to the requirements of ASTM D5249. Sealant shall
be a compatible sealant as recommended by the rod manufacture. Backer rod sizes shall conform
to Table 4-29.

Table 4-29: Backer rod sizes

Joint width after preparation

Rod diameter

8 mm

9 mm

13 mm

16 mm

19 mm

25 mm

32 mm

38 mm

50 mm

Material containing bitumen or solvents shall not be used with thermosetting chemically curing
sealants.

4.3.15.4

Joint Sealants

Sealers for joints not coming in contact with bituminous materials shall be a 2-component, cold-
curing polysulphide liquid polymer meeting Federal Specification, TT-S-227e, Type II, Class A, or as
approved by the Engineer or as shown in the Contract plans. Sealer shall be gun grade, or Type II,

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suitable for both horizontal and vertical joints. Where a primer is to be used in conjunction with the
sealant, it shall be of the prescribed proprietary material.

For proprietary asphalt-rubber products, the Contractor shall furnish the following:

1. Source and grade of asphalt binder

2. Total granulated rubber content and mass, as percent of the asphalt-rubber mixture

3. Granulated rubber types and content of each type, if blend

4. Mass as a percent of combined rubber

5. Gradation of granulated rubber

6. Type of asphalt modifier, if any

7. Quantity of asphalt modifier and mass as a percent of asphalt binder

8. Heating and application temperatures

9. Manufacturer's recommended application procedures

10. Other additives

Thermosetting chemically curing sealants shall comply with the requirements of ASTM C920. Final
international rubber hardness degree (IRHD) hardness of the sealant shall be 20 +5. Silicone
sealants shall comply with the requirements of the project particular specifications. Other sealants
may be used, if approved by the Engineer, after the Contractor has furnished the Engineer with full
information and specifications.

4.3.15.5

Hot-poured Joint Sealants

Hot-poured joint sealants shall meet the requirements of ASTM D6690 and be sampled and tested
per ASTM D5167 and ASTM D5329. In addition, the sealant shall have a flash point per AASHTO T
48 of 205° C minimum.

Physical properties of the joint sealer, when mixed in accordance with the manufacturer’s
recommendations, shall be per Table 4-30.

Table 4-30: Poured rubber joint sealer

Property

Criteria

Colour

Gray or black

Viscosity

Pourable and self-levelling at 10ºC

Application life

≥ 3 hours at 22º C and 50 % relative humidity

Set to touch

≤ 24 hours at 22º C and 50 % relative humidity

Curing time

≤ 96 hours at 22º C and 50 % relative humidity

Non-volatile content

≥ 92 %

Hardness rating (durometer

“Shore A”) 5 to 35

Resiliency

≥ 80 %

Bond test methods

In accordance with this section of the standard
specifications

Note 1: Viscosity and application life may be waived if the material is mixed and placed by a
pump and mixer approved by the Engineer. Suitable primer, if required by the manufacturer, shall
be furnished with each joint sealer. Primer shall be suitable for brush or spray application at 10ºC
or higher and shall cure sufficiently at 10º C to pour the joint within 24 hours. It shall be considered

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Property

Criteria

as an integral part of the sealer system. Any failure of the sealer in the test described herein,
attributable to the primer, shall be grounds for rejection or re-testing.

Acceptance of joint sealing compound for use on a project shall be on the basis of laboratory tests
of samples representative of each batch of material to be used on the job. A period of at least two
weeks shall be allowed for completion of tests. Each container of the compound shall be clearly
identified by its batch number.

Bond test for joint sealants shall be made per the following procedure:

a. Scope: This method covers the bond test for joint sealers.

b. Bond test apparatuses include the following:

1. Bond extension apparatus shall consist of an extension machine, similar to that described

in federal specifications, SS-R-406, so designed that the specimen can be extended for four
hours at a uniform rate of approximately 3.175mm per hour. It shall consist essentially of
one  or  more  screws  rotated  by  an  electric  motor  through  suitable  gear  reductions.  Self-
aligning  plates  or  grips, one  fixed  and  the  other carried  by  the  rotating  screw  or  screws,
shall be provided for holding the test specimen in position during testing. Machines must be
capable of reversing themselves for the recompression cycle. Bond extension machine shall
be housed in a refrigeration unit capable of maintaining a temperature of -18° C ±2° C.

2. Concrete blocks shall measure 25.4 mm by 76.2 mm by 50.8 mm.

3. Spacers made of brass or steel shall measure:

i. 152.4 mm by 25.4 mm by 12.7 mm, or

ii. 50.8 mm by 25.4 mm by 12.7 mm

4. Release agents shall consist of 50 % talc, 35 % glycerine, and 15 % water-soluble medical

lubricant blended into a smooth paste, where percentages are by weight.

c. Bond test preparation includes the following:

1. Prior to use, the cured blocks shall be removed from storage in 98 % relative humidity, and

acid etched with hydrochloric acid. Blocks shall be rinsed with water, wiped and allowed to
surface dry before using. Three prepared blocks shall then be placed on a glass plate and
a  spacer  152.4  mm  by  25.4  mm  by  12.7  mm  placed  between  them.  At  each  end  of  the
spacer block, a spacer block 50.8 mm by 25.4 mm by 12.7 mm shall be placed on end. Prior
to  using,  the  spacer  blocks  shall  be  coated  with  a  release  agent.  When  the  blocks  are
pushed together and secured with rubber bands, a joint that measures 152.4 mm by 25.4
mm by 12.7 mm in size is formed. Hot-poured joint sealer, prepared as per ASTM D 5167,
is poured in the formed joint to the top of the spacer blocks. Test specimens shall be allowed
to cool at standard conditions at least 2 hours; they shall be flush with the top and bottom
of  the  block;  and  shall  be  trimmed  using  a  heated  metal  knife.  Test  specimens  shall  be
placed in a freezer or extension chamber to equilibrate to testing temperature for at least 4
hours prior to first extension.

Two component joint sealers shall be prepared according the manufacturer’s
recommendations and poured in the formed joint to the top of the spacer blocks. Allow to
cure for 96 hours.

3. Three samples are required for each test.

d. Bond test procedures consist of the following:

1. Remove the spacers and insert the test specimens in the clamps of the extension machine.

Bond extension machines must be at -18° C ±2° C. Blocks shall then be extended to 12.7
mm in approximately 4 hours. Specimen shall be removed within 30 minutes post extension
and immediately inspected for obvious separations. Spacer strips shall be replaced and the

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blocks allowed to recompress at room temperature for 2 hours. This completes one cycle.
Specimens shall be returned to the freezer for at least 4 hours prior to the next extension.
This cycle shall be repeated 2more times for 3 total test cycles. Immediately following final
extension cycle, the Contractor shall determine conformance to respective material
specifications.

2. Development of any crack, separation, or other opening in the joint sealer or between the

joint sealer and the block shall be considered as a failure to pass the bond extension test.

4.3.15.6

Joint Mortar

A  completed mortar joint  shall  be  formed  with  a bead  on  the  outside  and  finished  smooth  on  the
inside of the sections and cured per the manufacturer’s recommendations.  Masonry mortar shall be
proportioned to meet the requirements of Article 4.3.10.4.

4.3.15.7

Bond Breakers

Bond breaker shall be a nonstaining type which will provide positive bond prevention. Polyethylene
tape-coated paper, metal foil, or similar material may be used where bond breakers are required.

4.3.16

Waterstops

Waterstops shall be of the type, size, and shape specified in the Contract documents. They shall
conform to the requirements of Article 21.9.1.6 of Chapter 21, Concrete Structures, of theses
standard specifications.

4.4

Construction Requirements

The concrete construction shall be as indicated on the Contract plans, as specified herein and as
directed by the Engineer.

4.4.1

Placing Concrete

Prior to the start of concrete placement of any element of the work, the Contractor shall review his
concrete placement methodology and program with the Engineer, unless this review requirement is
otherwise waived by the Engineer.  Contractor’s concrete placement methodology and program shall
be included in his program of works submittal, which shall meet the requirements of Section 1.6.2.
This  program  of  works  may  need  to  be  updated  by  the  Contractor  for  any  specific  concrete
placement, if directed by the Engineer.

Concrete shall be placed immediately after mixing by the Contractor. Contractor shall provide
sufficient capacity in the concrete producing plant and concrete transporting arrangements to avoid
cold joints. Cold joints are defined as locations where one concrete pour ends and becomes non-
plastic before the next concrete pour begins.

Transport of concrete from the mixers to the place of final deposit shall be by methods that prevent
the separation, loss, or contamination of any of the ingredients. Any method using pipes or chutes
for  transporting  concrete  will  not  be  permitted,  except  with  the  written  approval  of  the  Engineer.
Engineer may require that all structural concrete mixing, placement, and curing be accomplished in
shaded  areas.  Concrete  shall  not  be  placed  in  locations  where  nearby  vibrations  could  harm  the
concrete’s initial set or strength.

Concrete shall always be plastic and workable. Maximum time to discharge beyond the requirements
of Article 4.3.12.7 may be reduced by the Engineer to ensure plasticity and workability.

Methods for placing and consolidating concrete shall:

Deposit concrete as near its final position as possible

Place each layer of concrete before the previous layer commences to set

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Produce a compact, dense, homogeneous, and impervious concrete with smooth faces on

exposed surfaces substantially free from water and air pockets, or honeycombs

Work the concrete around the reinforcement steel, ducts, embedded fittings, and into the

corners of the formwork

Methods for placing and consolidating concrete shall not:

a. Leave a line of separation between layers

b. Segregate materials or aggregates

c. Displace reinforcing steel

d. Cause water to collect at the ends, corners, or along the faces of the forms

e. Move concrete over long distances

f. Allow surface water, such as rain, to affect or damage surface mortar quality or cause a flow

or wash the concrete surface

g. Allow concrete to free fall more than 1 m

To convey the concrete as near as possible to its final position, drop chutes of rubber or metal
conforming to the chutes, troughs, and conveyor belts requirements in Article 4.4.1.1 shall be used
for small sections and bottom dump buckets or other suitable vessels for large sections. All vibration,
consolidation, and finishing operations shall occur immediately after concrete is placed in its final
position. Plastering is not permitted.

Prior to concrete placement for any part of the works, the Engineer shall evaluate and approve the
following:

1. Placement of reinforcement steel

2. Method and sequence of placing concrete

3. Formwork

4. Depth and character of foundation

Immediately prior to concrete placement for any part of the works, the conditions of forms and
foundations shall be:

a. Thoroughly clean, with no dirt, shavings, loose stones, or other debris

b. Free from material that might adhere to or discolour the concrete

c. Free from standing water. Contractor shall remove standing water by pumping, if necessary.

d. Saturated with water, for foundations, excavations, and absorbent form materials such as

timber

e. Treated with a non-staining material to prevent adherence to the concrete, for exposed

surfaces

After acceptance, concrete shall not be modified by the addition of water or in any other manner to
facilitate handling or for any other reason.

Thickness of the layers shall be:

150 mm to 300 mm for reinforced concrete

Up to 450 mm for unreinforced concrete

As instructed by the Engineer, dependent on the width of forms, amount of reinforcement and

the necessity of placing each layer before the previous one commences to set

To protect the initial set of  the concrete, the  Contractor shall provide the following protections for
freshly  placed  concrete  for  at  least  72  hours  after  the  time  of  placing  and  until  the  Engineer
determines the concrete is not vulnerable to these factors. Contractor shall:

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a. Prevent jarring of the forms

b. Prevent strain on the ends of projecting reinforcement steel

c. Install fencing or otherwise prevent persons from walking or placing articles on the concrete

d. Protect the concrete from rain, dust storms, chemical attack, and the harmful effects of sun,

heat, wind, flowing water, vibrations, and shocks.

Concrete washout water shall be collected and disposed of in accordance with all applicable
regulations. In no case shall washout water be allowed to enter any storm drains or other surface
waters.

If a concrete pump is used as the placing system, the pump priming slurry shall be discarded before
placement.  Initial  acceptance  testing  may  be  delayed  until  the  pump  priming  slurry  has  been
eliminated. Eliminating the priming slurry from the concrete may require that several cubic metres of
concrete  are  discharged  through  the  pumping  system  and  discarded.  Use  of  a  concrete  pump
requires a reserve pump or other backup equipment at the site. When concrete pumps are used for
placement,  a  Contractor

’s representative shall, prior to use on the first placement of each day,

visually inspect the pumps’ water chamber for water leakage. Pumps that allow free water to flow
past the piston shall not be used by the Contractor.

Any section of defective concrete shall be removed at the Contractor

’s expense.

4.4.1.1

Chutes, Troughs, and Conveyor Belts

All chutes, troughs, and pipes shall be kept clean and free from coatings of hardened concrete by
thoroughly flushing with water after each run. Water used for flushing shall not be discharged into
the works. No aluminium chutes, tremies, troughs, or conduits shall be used to pump or place
concrete.

Chute lengths and slopes shall not cause segregation. Where steep slopes are required, chutes
shall be equipped with baffle boards or be in short lengths that reverse the direction of movement.
Spouts and baffles shall be provided at the lower end to minimise segregation.

If the concrete will drop more than 1 m, it shall be deposited through a sheet metal or other approved
conduit. If the form slopes, the concrete shall be lowered through approved conduit to keep it from
sliding down one side of the form.

To prevent segregation, the maximum length of any conveyor belt used to transport concrete shall
be 90 m. If concrete requires protection from the sun or rain, the Contractor shall cover the belt.

4.4.1.2

Continuity of Concrete Work

Casting of concrete shall not commence until a sufficient quantity of approved material is at hand to
ensure continuity of operation, nor shall work commence until there is sufficient equipment in reserve
in case of breakdown.

Concreting in any one part or section of the work shall be carried out in one continuous operation
and no interruption of concreting work longer than 30 minutes shall be allowed unless the Engineer
approves a longer time. Each layer shall be placed and consolidated before the preceding layer
takes initial set.

Fresh  concrete  shall  not  be  placed  against  concrete  that  has  been  in  position  for  more  than  30
minutes  unless  a  construction  joint  has  been  formed.  If  a  longer  interruption  is  allowed,  no  fresh
concrete shall be deposited on or against the concrete placed before the interruption until the latter
is  sufficiently  set to  resist  injury, at  least  one  hour.  Same  shall  apply  to adjacent  pours  at  abrupt
changes in sections. Particular care shall be taken to ensure that partially set concrete shall not be
damaged by shock or any other cause whatsoever.

If directed by the Engineer, required in the Particular Specifications, or shown in the Contract plans,
the Contractor shall place concrete in any particular section of the works without any interruption
whatsoever from the beginning to the end of the operation.

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4.4.1.3

Hot Weather Protection and Temperature Limits

When the shade air temperature is 32° C and rising, the Contractor shall take special precautions
during all concrete operations to prevent the concrete temperature from exceeding 32° C prior to
placement. Concrete that fails to conform to the maximum temperature requirement prior to
placement shall be rejected.

Fresh concrete placed at air temperatures exceeding 32° C shall be shaded from the direct rays of
the sun to the satisfaction of the Engineer. Concrete is not to be mixed or placed without special
protection and precautions, as approved by the Engineer, when the shade air temperature is 40° C
or above.

To maintain a concrete placement temperature less than 32° C, the Contractor may implement any
combination of the following methods:

a. Shade or cool the aggregate stockpiles

1. Sprinkle coarse aggregate with water

Monitor the pile’s moisture content and the mixing water to account for the free water
in the aggregate

ii.

Remove from at least 300 mm above the bottom of the piles

2. Sprinkling of fine aggregate piles with water shall not be allowed

b. Shade the concrete mixing plant

c. Cool the mixing water

1. By refrigeration

2. By liquid nitrogen

3. By substituting well-crushed ice of a size that will melt completely during mixing for part of

the mix water on a kg-for-kg basis

d. Screen and cover concrete in transit, concrete placement, and concrete curing to protect it

from wind and sun

e. Sprinkle forms, subgrade, and reinforcing steel with cool water just prior to placement of

concrete to cool all concrete-contact surfaces to less than 32°C before placement.

In hot weather, the Contractor shall minimise the time between mixing and placing and shall not
permit mixer trucks to remain in the sun while waiting to discharge concrete. Chutes, conveyors, and
pump lines shall be shaded. Curing shall commence immediately after concrete has been placed.

If the evaporation rate at the concreting site is 0.5 kg/m

of surface per hour or more, the Contractor

shall surround the fresh concrete with an enclosure to protect the concrete from wind blowing across
its surface until the curing compound is applied.

4.4.1.4

Concrete Exposed to Seawater

All concrete placement shall be done in the dry where the completed structure will be in contact with
seawater or brackish ground water. Prior to removing dewatering and cofferdams, all exterior
surfaces of concrete exposed to seawater or brackish ground water shall be cured and water
proofing or protection coatings applied, as required in the Contract plans or Particular Specifications.

4.4.1.5

Concrete Exposed to Alkaline Soils or Water

Requirements for concrete in seawater shall also apply to concrete in alkaline soils or water. In
addition, the Contractor shall:

1. Let the concrete set at least 30 days, longer if possible, before allowing soil or water to contact

it directly

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2. Vibrate each batch of concrete immediately after it has been placed into the forms, using

enough vibrating tampers to do this effectively, and

3. Hand tamp, if necessary, to produce smooth, dense outside surfaces

4.4.1.6

Vibration of Concrete

Unless otherwise permitted by the Engineer, concrete shall be compacted by means of vibrators.
Enough vibrators shall be supplied by the Contractor to consolidate the concrete, according to the
requirements of this section. Standby vibrators shall also be made available by the Contractor in
case of breakdowns. At least 2 vibrators shall be available at locations in which more than 25 m

concrete is to be placed. The placement of the vibrators shall be strictly vertical to avoid air
entrapment in the concrete. The size of the vibrators shall be for the intended purpose and approved
by the Engineer as per the method statement or Inspection and Testing Plan (ITP).

Each vibrator shall meet the following requirements:

a. Be designed to operate while submerged in the concrete

b. Vibrate at a rate of at least 7,000 pulses per minute

c. Be of a diameter that is compatible with the spacing of the reinforcement, and

d. Receive the Engineer

’s approval on its type and method of use.

Immediately after the concrete is placed, vibration shall be applied in the fresh batch at the point of
deposit. Care shall be taken not to displace reinforcement nor to disturb or affect partially set
concrete. In vibrating the concrete, the Contractor shall:

1. Space the vibrators evenly, no farther apart than 10 times the diameter of the vibrator

2. Ensure that vibration intensity is great enough to visibly affect a weight of 25 mm slump

concrete across a radius of at least 460 mm

3. Insert the vibrators slowly to a depth that will effectively vibrate the full depth of each layer,

penetrating into the previous layer so that the fresh concrete will be worked into the previously
placed layer on multilayer pours

4. Protect partially hardened, or non-plastic, concrete by preventing the vibrator from penetrating

it or making direct contact with steel that extends into it. Vibrators shall not penetrate non-
plastic concrete when only the vibrator’s own weight is applied

5. Continue each immersion in one place until shortly after air bubbles cease to appear on the

surface of the concrete, and not long enough to form pools of grout

6. Continue vibration long enough to consolidate the concrete thoroughly, but not so long as to

segregate it

7. Withdraw the vibrator slowly, gradually, and vertically when the process is complete to ensure

no air pockets are formed

8. Not use vibrators to move concrete from one point to another in the forms, and

9. Avoid vibrator contact with reinforcement and formwork shall.

When vibrating and finishing top surfaces that shall be exposed to weather or wear the Contractor
shall not draw water or laitance to the surface. In high lifts, the top layer shall be shallow and made
up of a concrete mix as stiff as can be effectively vibrated and finished.

To produce a smooth, dense finish on outside surfaces, the Contractor shall hand-tamp the concrete.

Vibration shall be applied by experienced labourers. Previously completed concrete pours shall not
be subjected to disturbance by vibration within 4 to 24 hours of having been compacted. Vibrators
shall not be attached to reinforcement in any circumstance.

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4.4.1.7

Underwater Concrete

Placing concrete under water shall be allowed only in circumstances where it is not feasible to
dewater the location before the concrete is placed. No concrete shall be placed in running water.
Placement of concrete underwater shall be done using the methodology required in Section 21.7.4
of Chapter 21, Concrete Structures, of these Standard Specifications.

4.4.2

Curing Concrete

All  newly  placed  concrete  shall  be  cured,  which  shall  begin  immediately  after  finishing.  Concrete
surfaces  shall  receive continuous  moisture  for  at  least  7  days. When  continuous  moisture  or  wet
curing is required, the Contractor shall keep the concrete surfaces wet with water during curing.

Curing shall be performed so that moisture is always present. Improperly cured concrete shall be
considered defective and evaluated for rejection and reduced payment. Placing operations shall be
stopped by the Engineer until the Contractor can put proper curing procedures into effect.

Adopted curing method shall be subject to the Engineer's approval and shall not cause staining,
contamination, or marring of the surface of the concrete. Method A shall be used for curing exposed
concrete surfaces, unless otherwise approved by the Engineer. When permitted in writing by the
Engineer, the Contractor may use one of the following methods of curing exposed concrete surfaces.

4.4.2.1

Method A: Supplying Continuous Moisture

Continuous moisture shall  be  provided  by the  Contractor  by  watering  a covering  of  heavy-quilted
blankets or burlap and covering with white reflective type sheeting, or by wetting the outside surfaces
of wood forms. Either approach shall be executed such that concrete surfaces remain wet with water
continuously. Watering shall include supplying additional moisture by ponding, sprinkling, or fogging.
Sawdust  or  coverings  that  cause  unsightly  discolouration  of  concrete  shall  not  be  used  by  the
Contractor.  Coverings  shall  be  placed  as  soon  as  possible  after  finishing  operations  have  been
completed and there is no danger of surface damage. Coverings shall be kept continuously moist;
any method that results in the concrete being alternately wet and dry shall be considered an improper
curing procedure.

4.4.2.2

Method B: Preventing Moisture Loss

This method shall consist of preventing moisture loss from the concrete. It may be done with a
combination of waterproof paper, white reflective plastic sheeting, or liquid membrane-forming curing
compound. Paper and sheeting shall be securely anchored at the edges so as to effectively minimise
moisture loss.

If a formed surface is to be rubbed, the concrete shall be kept moist before and during the rubbing,
and the curing shall be initiated immediately following the first rub while the concrete surface is still
moist.

Runoff water shall be collected and disposed of in accordance with all applicable regulations. In no
case shall runoff water be allowed to enter any lakes, streams, or other surface waters.

Steam curing concrete is acceptable for precast units.

a. Waterproof Paper

Waterproof paper shall be the widest practicable width and adjacent sheets shall overlap a minimum
of 150 mm and shall be tightly sealed with a pressure sensitive tape, mastic, glue, or other approved
methods to form a complete waterproof cover of the entire concrete surface. Paper shall be secured
so that wind shall not displace it. If any portion of the sheets is broken or damaged before expiration
of the curing period, the Contractor shall repair the broken or damaged area immediately. Sections
that have lost their waterproof qualities shall not be used.

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b. White Reflective Plastic Sheeting

White reflective plastic sheeting shall be used in the same manner as required for waterproof paper
and shall comply with Section 4.3.134.3.13.1.

c. Curing Compounds

Only Type 2 liquid membrane-forming curing compounds complying with AASHTO M 148 may be
used, when approved by the Engineer, as the initial and final curing agents on concrete, subject to
the following limitations:

If the membrane film is broken or damaged at any time during the curing period, the area or

areas shall be recoated to the original requirements

Curing compounds shall be applied to unformed surfaces as soon as the water sheen has

practically disappeared from the concrete, or as soon as the forms have been removed from
surfaces not to be rubbed

Curing compounds shall not be used on areas receiving a rubbed finish

If there is to be any delay in applying curing compound, the surface shall receive moist curing

until the compound can be applied

Curing compounds shall be applied with equipment that shall produce a fine spray, and all

compounds shall be thoroughly agitated just prior to use. Surfaces shall be sprayed again
immediately at right angles to the first application with a rate for each application at not less
than 1 litre for each 3.6 m

of surface. Care shall be taken to prevent application to joints where

concrete bond is required to reinforcement steel, and to joints where joint sealer is to be placed

No curing compound shall be used on fixed-form concrete barriers

Timber formwork covering the concrete shall be moistened with water at frequent intervals to keep
it from drying during the curing period. Metal formwork exposed to the sun must be shaded from its
direct rays, painted white, or otherwise protected during the curing period. When forms are removed
before the end of the curing period, specified curing procedures shall be implemented by the
Contractor and continued until the end of the specified curing period.

4.4.2.3

Method C: Curing Compound

Under the curing compound method, the Contractor shall:

a. Spray 2 coats of clear curing compound, Type 1D, on the concrete surface after the free water

has disappeared. Coverage of combined coats shall be at least 4 L/15 m

b. Cover the structure with white, reflective sheeting for at least 10 days, beginning no later than

the morning after applying the curing compound.

c. After the 10-day curing period, remove the curing compound as necessary by light

sandblasting or by spraying with a high-pressure water jet to produce an even surface
appearance. Water jet equipment shall use clean fresh water and shall produce at least 175
kg/cm

at the nozzle with a discharge of at least 15 l/minute. Nozzles shall have a 25

tip and

shall be held no more than 250 mm from the surface being cleaned. Curing compounds or
concrete sealers proposals, made by the Contractor, shall be evaluated by the Engineer and
approvals shall be made in writing. As a minimum, the Contractor

’s proposal shall include the

following:

1. Product identity

Manufacturer’s recommended application rate

3. Method of application and necessary equipment

4. Material safety data sheet (MSDS)

5. Sample of the material for testing

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Contractor shall allow 14 working days for evaluating the proposal and testing the material.

4.4.2.4

Method D: Wet Blankets

Under the wet-cure method, the Contractor shall:

1. Provide an initial cure period by continuous fogging or mist spraying for at least the first 24

hours.

2. After the initial cure period, cover the structure with a heavy quilted blanket.

3. Keep the blankets continuously wet for at least 10 days. No additional finishing is required at

the end of the curing period.

In the event any member or portion of the work prove, after removal of the formwork, to be of inferior
workmanship or to be in any way whatsoever defective, or should crushing tests on samples taken
from the work show that the concrete used therein is of inferior quality, such work shall, at the
discretion of the Engineer, be cut out and replaced.

4.4.2.5

Curing Slip-form Construction

Slip-form construction shall be finished by the Contractor by:

1. Steel trowelling to close all surface pockmarks and holes; and

2. For plain surfaces, lightly brushing the front and back face with vertical strokes and the top

surface with transverse strokes.

After finishing, the Contractor shall cure the slip-form construction by using either Method C, curing
compound, or Method D, wet blankets, as described below.

Where slip-form work was performed, the concrete shall be protected against the weather and rapid
drying out by means of a 4 m wide skirt attached to the lower perimeter of the formwork and hanging
over the working platform. Skirts shall consist of hessian in the summer months and of canvas or
other suitable material in winter and shall be weighted at the bottom to prevent flapping in windy
conditions. To wet the concrete, the Contractor shall use a fixed spraybar, which shall be connected
to a suitable high-pressure water supply, along the full-length of the sliding formwork.

4.4.2.6

Insulated Curing

The insulated curing method shall allow for a waterproof cover with a 1000 gauge polyethelene sheet
and then insulated with 50mm rigid closed cells extruded polystyrene thermal board insulation. Over
the polystyrene thermal board, a 1000 gauge polyethelene sheet is again placed to avoid moisture
ingress into the Styrofoam/thermal board. The whole system is to be wrapped properly to avoid
displacements during the curing period (normally 10 days for pozzolanic concrete).

4.4.3

Concrete Finishing

All concrete shall show a smooth, dense, uniform surface after the forms are removed. If it is porous,
the Contractor shall bear the cost of repairing it. Contractor shall clean and refinish any stained or
discoloured surfaces that may have resulted from their work or from construction delays.

Surfaces that are specified in the Contract documents to be “troweled” shall after the concrete is
partially set, finished to a smooth surface by troweling with a steel trowel until a slick surface free of
bleed water is produced. Surface shall then be brushed with a fine brush using parallel strokes.

Surface finishes for formed concrete surfaces shall be classified as follows:

•

Class 1: Ordinary surface finish

•

Class 2: Rubbed finish

•

Class 3: Tooled finish

•

Class 4: Sandblast finish

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•

Class 5: Wire brush or scrubbed finish

Requirements for Class 1 to 5 surface finishes shall be in accordance with Section 21.12 of Chapter
21, Concrete Structures, of these standard specifications.

All concrete shall be given a Class 1, Ordinary Surface Finish, and if further finishing is required,
such other type of finish as is specified. If not otherwise specified in the Contract documents,
exposed surfaces shall be given a Class 2, Rubbed Finish. Class 3, 4, or 5 finishes shall be applied
only where specified in the Contract documents. Surfaces covered with fill do not require a surface
finish.

All surfaces of concrete that are not placed against forms shall be finished in accordance with Section
21.10 of Chapter 21, Concrete Structures, of these standard specifications.

4.4.4

Construction and Expansion Joints

Construction joints shall be installed:

To the positions, dimensions, and types shown in the Contract plans.

As specified herein.

As approved by the Engineer, including additions, deletions, or relocations from the information

shown in the Contract plans.

As requested in writing by the Contractor, accompanied by a drawing that depicts them, and

approved by the Engineer.

In response to breakdowns or other unforeseen and unavoidable delays, with the Engineer

’s

approval and with the Engineer

’s designation of bonded or unbonded.

Any added costs that result from Contractor-initiated changes shall be borne by the Contractor.

Concreting shall be carried out continuously at construction joints, which shall be formed at right
angles to the axis of the member. Construction joints shall be formed neatly with grade strips or other
approved methods. Irregular or wavy pour lines will not be accepted by the Engineer. Wire mesh
forming material shall not be used. All joints shall be horizontal, vertical, or perpendicular to the main
reinforcement. An edger shall not be used on any construction joint, and the Contractor shall remove
any lip or edging before making the adjacent pour. Face edges of all joints that are exposed to view
shall be carefully finished true to line and elevation.

Construction joints in abutment walls, wing walls, and barrels of box culverts shall be placed at
intervals not exceeding 9 m, except as otherwise indicated on the Contract plans or approved by the
Engineer.

For definitions of the various types of joints refer to the AASHTO Load and resistance factor design
(LRFD) Bridge design specifications.

Waterstops shall be installed in all joints where the Engineer determines that ingress or egress of
water is detrimental regardless of whether such waterstops are shown on the Contract plans.

If the Contract plans require a roughened surface on the joint, the Contractor shall strike it off to
leave grooves at right angles to the length of the member. Grooves shall be 12 mm to 25 mm wide,
6 mm to 12 mm deep, and spaced equally at twice the width of the groove. If the first strike-off does
not produce the required roughness, the Contractor shall repeat the process before the concrete
reaches initial set. Final surface shall be clean and without laitance or loose material.

If the Contract plans do not require a roughened surface, the Contractor shall include shear keys at
all construction joints. These keys shall provide a positive, mechanical bond. Shear keys shall be
formed depressions and the forms shall not be removed until the concrete has been in place at least
12 hr. Forms shall be slightly bevelled to ensure ready removal. Raised shear keys are not allowed.

Shear keys for the tops of beams, at tops and bottoms of boxed girder webs, in diaphragms, and in
crossbeams shall:

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1. Be formed with 50 mm by 200 mm wood blocks

2. Measure 200 mm lengthwise along the beam or girder stem

3. Measure 100 mm less than the width of the stem, beam, crossbeam, or other adjacent element

as measured transverse to the stem

4. Be spaced at 400 mm centre-to-centre.

Unless the  Contract plans  show otherwise, in locations not named above, shear keys shall equal
approximately one-third of the joint  area and shall be approximately 40 mm deep. Before placing
new concrete against cured concrete, the Contractor shall thoroughly clean and roughen the cured
face and wet it with water. Before placing the reinforcing mat for footings on seals, the  Contractor
shall:

a. Remove all scum, laitance, and loose gravel and sediment

b. Clean the construction joint at the top of the seals

c. Chip off any high spots on the seals that would prevent the footing steel from being placed in

the position required by the Contract plans.

Shear keys formed into, or out from, the surface of the previously placed concrete, or steel dowels,
shall be used where required. Shear keys formed into the concrete shall be formed by the insertion
and subsequent removal of bevelled wood strips that shall be thoroughly saturated with water prior
to insertion. Steel dowels may, at the discretion of the Engineer, be used in lieu of keys. Size and
spacing of the keys and dowels shall be as shown in the Contract plans, or as directed by the
Engineer.

4.4.4.1

Preparing the Surfaces

When the concrete has set and while it is still green, the surface film and all loose material shall be
removed  without  disturbing  the  aggregate  by  means  of  a  water  jet  assisted  by  light  brushing  to
expose the aggregate and leave a sound, irregular surface. Where this is not possible, the surface
film  shall  be  removed  after  the  concrete  has  hardened,  by  mechanical  means  appropriate  to  the
degree  of  hardness  of  the  concrete  so  as  to  expose  the  aggregate  and  leave  a  sound,  irregular
surface. Roughened surfaces shall be washed with clean water to remove all laitance, dirt, and loose
particles.

Surface retarding agents may be used only with the Engineer

’s approval.

4.4.4.2

Placing Fresh Concrete at Construction Joints

Where fresh concrete is placed on the same day as when the construction joint was formed, the
fresh concrete shall be cast directly against the face of the construction joint.

When concreting recommences a day or more after the construction joint has been formed, the
Contractor shall abide by the following procedure:

1. Construction joints shall be kept constantly wet for at least 6 hours. Surface shall be in a

saturated, surface dry condition when concreting begins again.

2. Any dirt, excess water, and loose particles shall be removed prior to re-concreting.

3. For horizontal construction joints a 25 mm thick concrete layer of the same grade of concrete

made richer by reducing the coarse aggregate content by 25 % shall be placed on the joint
plane immediately before concreting.

4. For vertical construction joints the fresh concrete shall be placed against a surface prepared

as described above to a saturated, surface-dry condition.

Abu Dhabi, United Arab Emirates. STANDARD CONSTRUCTION SPECIFICATIONS (PART 1 - ROADS, Second Edition 2020) - page 26