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

3.2.3.1 Description

Item of work consist of furnishing and placing one or more layers of wet mix macadam, including
additives if required, on a prepared surface in accordance with these specifications and in conformity
with the lines, grades, thicknesses and typical cross-sections shown on the Contract plans or
established by the Engineer.

3.2.3.2 Materials

All aggregates for Wet Mix Macadam shall consist of crushed gravel, crushed rock or stone
fragments obtained by crushing gravel that has first been screened in such a manner that no less
than 90 % of the material to be crushed is retained on a 4.75 mm sieve.

Amount of crushing shall be regulated so that at least 100 %, by weight, of the pieces retained on
the 4.75 mm sieve have at least 1 fractured face.

All aggregates for wet mix macadam shall conform to the requirements of Table 3-7.

Table 3-7: Physical requirements of aggregate for wet mix macadam

Loss of sodium sulphate soundness test (AASHTO T 104)

10 % maximum

Loss of magnesium sulfate soundness test (AASHTO T 104)

12 % maximum

Loss of abrasion test (AASHTO T 96)

30 % maximum

Thin and elongated pieces, by weight (B.S. 812

)

5 % maximum

Friable particles (AASHTO T 112)

0.25 % maximum

Material for wet mix macadam shall conform to the requirements in Table 3-8.

Table 3-8: Material requirements for wet mix macadam

Standard sieve size

Percentage passing by

weight

50 mm

100

37.5 mm

95 – 100

19.0 mm

60 – 80

9.5 mm

40 – 60

4.75 mm

25 – 40

2.36 mm

15 – 30

600 µm

8 – 22

75 µm

0 – 8

Liquid limit (AASHTO T 89)

25 maximum

Plasticity index (AASHTO T 90)

4 maximum

Sand equivalent (AASTHO T 176)

45 minimum

Maximum dry density (AASTHO T 180)

2.20 gr./cc

CBR on remolded sample after 4 days soaking at 98 % MDD (AASHTO -

T193

80% Minimum

One sample every 1,000 m

shall be tested for grading, soundness, loss by abrasion, maximum dry

density, plasticity index, sand equivalent, and CBR. One in-situ density test shall be taken every 300
m

of laid wet mix macadam.

3.2.3.3 Construction Requirements

a. Subgrade Preparation

Unless other subgrade preparation is indicated on the Contract plans or as a pay item in the bills of
quantities, the Contractor shall, prior to the delivery of materials for the wet mix macadam, prepare
the roadbed surface by sprinkling, blading, rolling, and lightly scarifying where necessary, until the
proper cross slope is obtained. However, in the process of shaping an existing roadbed, the
originally compacted crust or top portion of the roadbed shall be disturbed as little as possible.

When completed and ready for wet mix macadam construction, the roadbed shall be well compacted,
smooth, hard and uniform, all irregularities having been bladed out and rolled down.

b. Compaction Trials

If  directed  by  the  Engineer,  prior  to  the  commencement  of  wet  mix  macadam  operations,  the
Contractor shall construct trial lengths, not to exceed 1 km.  Material used in the trials shall be that
approved  for  use  as  wet  mix  macadam  and  the  equipment  used  shall  be  that  accepted  as  the
Contractor

’s approved detailed list of resources.

Aim of these trials is to determine the adequacy of the Contractor

’s equipment, the loose thickness

measurements necessary to result in the specified compacted layer thickness, the field moisture
content, and the relationship between the number of compaction passes and the resulting density of
the material.

Contractor may proceed with wet mix macadam work only after the method and procedures
established in the compaction trial have been approved by the Engineer.

c. Method of Construction

Wet mix macadam shall be combined into a uniform mixture and water added only in a central mixing
plant before final placement of the material. Mixing and watering by windrows will not be permitted.
When binder is to be added, it shall be combined with the wet mix macadam by thoroughly mixing
the binder and wet mix macadam in the central mixing plant.

Moisture added to the aggregates shall be that required, as designated by the Engineer, to obtain
the specified density thereby preparing an aggregate completely ready for compaction after
spreading on the roadbed. In no case will wetting of aggregates in stockpiles or trucks be permitted.

Wet mix macadam shall be delivered to the roadbed as a uniform mixture and shall be placed on the
existing roadway, prepared subbase, or prepared subgrade, as the case may be, in a uniform layer
or layers not exceeding 150 mm in compacted thickness. Spreading shall be done by means of
approved self-propelled stone box spreader, distributing the material to the required width and loose
thickness. When the required thickness is greater than 150 mm, the materials shall be spread in
layers of equal thickness but no less than 100 mm.

Material shall be so handled, as to avoid segregation.  If an aggregate spreader causes segregation
in  the  material,  or  leaves  ridges  or  other  objectionable  marks  on  the  surface  which  cannot  be
eliminated  easily  or  prevented  by  adjustment  of  the  spreader  operation,  such  spreader  shall  be
removed and replaced by another box spreader.  No “skin” patching will be permitted.

No hauling or placement of material will be permitted when, in the judgment of the Engineer, the
weather or road conditions are such that hauling operations will cause cutting or rutting of the road
surface or cause contamination of the wet mix macadam.

Rolling  shall  be  continued  until  the  entire  thickness  of  each  layer  is  thoroughly  and  uniformly
compacted to the density specified.  Final rolling of the compacted wet mix macadam shall be done
with a self-propelled roller.  Rolling shall be accompanied by sufficient blading in a manner approved
by the Engineer, to ensure a smooth surface, free from ruts or ridges and having the proper section
and cross slope.  When additional water is required, it shall be added in the amount and manner
approved by the Engineer.  Each layer of wet mix macadam shall be completely compacted by the
Contractor and approved by the Engineer prior to the delivery of the materials for a succeeding layer.

Surface of the finished wet mix macadam will be tested with 5 m straight-edge by the Engineer at
selected locations.  Variation of the surface from the testing edge of the straight-edge between any
2 contacts with the surface shall at no point exceed 6 mm when placed on or parallel to the centerline
or 6 mm when placed perpendicular to the centerline of the roadway.  Wet mix macadam shall be
compacted to the thickness and cross section as shown on the Contract plans and shall not vary by
more than 5 mm from the required elevation.  All humps and depressions and thickness deficiencies
exceeding the specified tolerances shall be corrected by removing the defective work or by adding
new material, as directed by the Engineer.

If the material for the wet mix macadam is laid and compacted in more than 1 layer, the Contractor
shall plan and coordinate the work in such a manner that the previously placed and compacted layers
be allowed ample time for drying and the development of sufficient stability, before vehicles hauling
materials  for  the  succeeding  layers  or  other  heavy  equipment  are  permitted  on  the  wet  mix
macadam.  Prior to placing the succeeding layers of materials, the top of the under-layer shall be
made sufficiently moist to insure bond between the layers.  Edges and edge slopes of the wet mix
macadam shall be bladed or otherwise dressed to conform to the lines and dimensions shown on
the  Contract  plans  and  present  straight,  neat  and  workmanlike  lines  and  slopes  as  free  of  loose
material as practicable.

Contractor shall also plan the work and handle the various operations so that the least amount of
water will be lost by evaporation from uncompleted surfaces. If the Contractor delays placing of
succeeding layers of wet mix macadam material to the extent that additional water must be applied
to prevent raveling or excessive dripping, the application of such water shall be at the Contractor

’s

expense and not be considered as the basis for a Claim for additional compensation.  Water shall
be applied at such times and in such quantities as directed by the  Engineer.  If after the wet mix
macadam is compacted, any areas are above or below the proper grade and true elevations, such
areas shall be loosened and after having had additional materials added or excess material removed,
as the case may require, shall be reconstructed as described herein.  If after the wet mix macadam
is compacted any areas fail to meet the specified density and gradation requirements, such areas
shall be loosened or removed as directed by the Engineer and reconstructed as described herein.

Following the construction of the wet mix macadam, the compacted layer shall be maintained by the
Contractor at his expense. Contractor shall blade, broom, and otherwise maintains the wet mix
macadam, keeping it free from raveling and other defects until such time as the bituminous prime or
other surface is applied. Water shall be applied at such times and in such quantities as directed by
the Engineer.

Engineer shall determine when the surface of the wet  mix macadam is in the proper condition to
permit the bituminous prime and/or surfacing to be applied.  If the Contractor chooses not to apply
the bituminous prime and/or surfacing at that time, he must continue to maintain the surface of the
wet mix macadam, including the application of necessary water, at his expense until such time as
the  bituminous  prime  coat  and/or  surfacing  is  applied.    Any  additional  expense  incurred  by  the
Contractor  because  of  his  failure  to  apply  the  bituminous  prime  coat  and/or  surfacing  when  so
permitted by the Engineer will not be considered as the basis for a Claim for additional compensation.

3.2.4.1 Description

Cement stabilized subbase/base shall consist of material aggregate uniformly mixed with cement
and water, placed and compacted in one single layer on a prepared granular subbase in conformity
with the Contract plans and this specifications or as established by the Engineer. Thickness and
width of the cement stabilized subbase/ base layer shall be as shown on the Contract plans.

3.2.4.2 Materials

a. Mineral Aggregates

Mineral aggregates shall be either naturally occurring granular material or crushed stone or gravel
or combination thereof and shall conform to requirements in Table 3-9.

Table 3-9: Aggregates for cement stabilized subbase/base

Test

Limits

Sampling ASTM D75

Liquid limit BS 1377- 2 : Test 4.5

25 % max.

Linear shrinkage (BS 1377-2 Method 6.5)

3 % max.

Plasticity index (BS 1377- 2 Test 5.4)

4 max.

Aggregate crushing value (BS 812-110:1990)

25 % max.

Water absorption (ASTM C128 / C127)

2.0 % max.

Flakiness index (BS 812-105-105.1)

30 max.

Elongation index (BS 812-105-105.2)

30 max.

Los Angeles abrasion loss (ASTM C-131

or C-535 )

30 % max.

Soundness loss (ASTM C88) 5 cycles (magnesium sulfate)

12 % max

Organic Matter Content (BS 1377-3

Method 3)

0.2 % max.

Chloride Content (Acid Soluble) BS 812-117

1% max.

Sulfate Content (Acid Soluble) BS EN 1744-1

0.5% max.

Sand equivalent (ASTM D 2419).

45 min.

All of the combined aggregates retained on the Standard AASHTO 5 mm sieve shall have not more
than 5 % of flat elongated pieces and, when tested in accordance with AASHTO T-11

and AASHTO

T-27 shall conform to the grading limits (i.e. all in aggregate grading without cement) in Table 3-10.

Table 3-10: Combined aggregates grading limits

Sieve Size

Percent Passing

53 mm

100

37.5 mm

– 100

20 mm

– 90

Percent Passing

10 mm

– 75

5 mm

– 45

2.36 mm

– 30

0.600 mm

– 18

0.075 mm

– 6

Coarse aggregate shall consist of crushed rock only, each particle shall have a minimum of two
crushed face. Fine aggregate shall be crushed rock or naturally occurring material.

At least one sample from each stock pile every 1000 m

shall be taken for abrasion, sand equivalent,

plasticity index and grading.

b. Cement

Cement shall be sulfate resisting and shall conform to the latest standard requirements of AASHTO
M 85 for Type V. One 2 kg sample for quality test shall be taken from each 1,700 bags or equivalent.

c. Water

Water shall be clean and free from oil, alkali, vegetable matter, salt. Water shall be in sufficient supply
for mixing and curing. 4-litre sample shall be obtained prior to use from each source and at least
once a week during the production for quality.

d. Job Mix

At least 30 days prior to the date the Contractor intends to begin construction of the cement stabilized
upper subbase, and after receiving approval of the aggregates from the Engineer and after the
delivery on site of the cement specified for this work, the Contractor shall make written request for
the approved job-mix formula from the Engineer. Job-mix formula will be prepared by the Contractor,
and will be tested by the Engineer.

1. Mix Design

Job-mix formula shall combine the mineral aggregates with cement and water in such proportions
as to produce a mixture conforming to the following requirements:

i. Trial dry mix design shall be done so as to achieve the grading requirement as specified

above  and  to  achieve  maximum  density  (per  ASTM  D1557)  from  the  coarse  and  fine
aggregate  combination  (without  cement),  by  different  trials.  Modified  proctor  test  shall  be
done  in  150  mm  diameter  mould  to  achieve  maximum  dry  density  (MDD)  and  optimum
moisture content (OMC).

ii. 4 % cement by weight of total dry mix shall be added to the finalized gradation with maximum

density.

iii. Final checking of the gradation shall be conducted after the addition of the cement. All in

aggregate gradation shall be within design tolerance limit and the specification requirement.

iv. Cement (4% of total dry mix) plus varied amount of water (increment of +/- 1.0 % of OMC)

shall be added to final 3 trial design mixes after accounting for water absorption by
aggregates to ascertain the design optimum moisture content for workable laboratory mix.
Mixing of the design mixes shall be done in a mixer of adequate capacity to make at least 9
unconfined compressive strength (UCS) samples (ASTM D1633). Mixing time for the trial
mixes shall be 2 minutes in the mixer.

v. Consistency (workability) of the trial design mixes produced in laboratory shall be judged and

recorded after every 30 minutes of mixing the cement and water. Design OMC shall be
decided based on consistency observed after 60 minutes.

vi. UCS sample shall be prepared in a clean oiled/no sticky mould to avoid any damage to the

UCS sample. Casting of the UCS sample shall be done immediately after 60 minutes for all
the three trial design mixes in three layers and 56 uniformly distributed blows per layers.
Adequate care shall be taken to make the top surface of the UCS sample free of irregularity.
After casting, the UCS samples shall be kept in moist covered (with wet cloth) for 24 hours
at 16 to 27 degree centigrade. After 24 hours the sample shall be taken out of the mould
carefully and shall be put in water bath for curing for 3-day, 7 days and 28 day total duration
at 16 to 27 degree centigrade.

2. Test Method

Following laboratory test procedure shall be carried out for satisfactory results. Sample shall be
taken out of water bath one hour before the testing time. UCS sample shall be wiped around with
damp cloth to make it saturated surface dry (SSD). UCS specimens prepared and cured as above
shall be subjected to compressive strength tests in accordance with AASHTO T 22

(ASTM C39).

A plywood/packing shall be kept on top and bottom of the sample for uniform application of
loading. An approved calibrated universal testing machine (UTM) of adequate capacity shall be
used to apply the loading. Maximum loading to failure shall be recorded and reported as failure
load. Failure pattern shall be recorded and calculation of the unconfined compressive strength
shall be done by dividing the failure load to the average plan area of the sample. The density and
strength shall be as in Table 3-11.

Table 3-11: Minimum density and strength requirements

MDD as per BS 1377-4 test 3.7

2.1 mg/m

min.

Unconfined compression test at 7 days

6.0 ± 1 MPa

Strengths shall be obtained on the average of at least three specimens and individual test results
moving more than 15 % from the average shall be discarded.

3. Tolerances

All production mixture shall conform to the job-mix approved by the Engineer, within ranges of
tolerances as follows:

Aggregate passing 4.75 mm sieve or larger

+/- 5 %

Aggregate passing 2.00 mm sieve or larger

+/- 2 %

Cement

+/- 0.2 %

Water

+/- 1 %

Unconfined compressive strength

+/- 20 %

Each day the Engineer will take as many samples of the materials and mixtures as he considers
necessary for checking the required characteristics of the mixtures.

At least one set of 6 specimens shall be prepared during the placing operations, every 500 linear
metres of furnished mixture to check the required strengths of the mixture.

When unsatisfactory results or changed conditions make it necessary, the Engineer may require
that a new job-mix be prepared.

Should a change in material be encountered or should a change in a source of material be made,
a new job-mix formula shall be submitted and approved before the mixture containing the new
material is delivered. Job materials will be rejected if they are found not to have the characteristics
required by the established job-mix formula.

Sampling and testing shall be performed by the Contractor at his expense, under the observation
of the Engineer.

e. Plant and Equipment

Plant and equipment shall be according to the type and number outline in the Contractor

’s detailed

programme of works, as approved by the Engineer. All equipment, tools, machinery and plants must
be maintained in a satisfactory working condition.

3.2.4.3 Construction Requirements

Mixing of the aggregate, cement and water shall be accomplished by the plant-mixed method only.

a. Preparation of Granular Subbase

Top surface of granular subbase ready to receive cement stabilized upper subbase, (immediately
prior to spreading) shall conform to the compaction and elevation tolerance otherwise specified, and
shall be free of loose or extraneous material.

In hot weather, the top surface of granular subbase shall be moistened before spreading of the
cement stabilized upper subbase, in order to prevent evaporation.

b. General Requirements of Plant Mixed Method

Aggregates and cement shall be proportioned and mixed in accordance with the following:

Plant-mixed cement stabilized subbase/ base shall be mixed at a central mixing plant by either batch
type mixing using revolving blade or rotary drum mixers or by continuous type mixing as approved
of the Contractor. Aggregates and cement may be proportioned either by weight or by volume. Plant
shall be calibrated to produce the design mix proportion to the satisfaction of Engineer.

In all plants, the water shall be proportioned by weight or volume and there shall be means by which
the Engineer may readily verify the amount of water per batch or the rate of flow for continuous
mixing. Time of the addition of water or the points at which it is introduced into the mixer shall be as
approved by the Engineer.

Moisture content of the completed mixture shall be at least the optimum moisture content plus or
minus one percentage point at the point of delivery to the paving work site.

In all the plants, cement shall be added in such a manner that it is uniformly distributed throughout
the aggregates during the mixing operation.

Safe and convenient facilities shall be provided for sampling cement in the supply line to the weight
hopper or pugmill.

Charge in a batch mixer, or the rate of feed to continuous mixer, shall not exceed that which will
permit complete mixing of all the material. Dead areas in the mixer, in which the material does not
move or is not sufficiently agitated, shall be corrected.

Cement content of the completed mixture of cement stabilized upper subbase, after it has been
spread on the granular subbase and prior to initial compaction, shall meet the specified requirements
when sampled and tested.

Cement feeder and the aggregate feeders shall be equipped with devices by which the rate of feed
can be determined while the plant is in full operation.

c. Spreading Cement Stabilized Subbase/Base

Immediately prior to depositing plant-mixed cement stabilized subbase/base the area to be covered
shall be moistened and kept moist, but not excessively wet.

If less than 2 lanes are to be spread, not more than 2 hours shall elapse between the time of placing
the material in adjacent lanes to result in a 2-lane width. However, if traffic conditions preclude
placement of cement stabilised subbase/base in adjacent lanes within hours, the Engineer may
authorize such longer time as may be necessary.

Longitudinal construction joints shall fall within +/-300 mm of lane lines.

Cement stabilized subbase/base placed on areas inaccessible to mechanical spreading equipment
may be spread in one layer by methods approved by the Engineer. After spreading, the material
shall be thoroughly compacted to the required line grades, and cross section by means of pneumatic
tampers or with other compacting equipment which consistently obtains the degree of compaction
required.

In addition, spreading of cement stabilized subbase/base shall conform to the directions of the
Engineer.

Use of motor graders will not be permitted during the spreading and compacting operating. Motor
graders may be used to trim the edges and surface of the cement stabilized subbase/base after
compaction in order to finish the subbase within the tolerances specified.

Mixture  shall  be  spread  in  one  operation  with  a  self-propelled  mechanical  spreader  ready  for
compaction  without  further  shaping.    Equipment  not  propelled  by  the  unloading  vehicle  will  be
considered self-propelled.  Spreader shall be provided with a screed that strikes off and distributes
the material to the full width being spread and to the surface tolerances specified.  Screed shall be
adjustable to produce the required cross section.    Screed action includes any cutting, crowding, or
other practical motion that produces a finished surface texture of uniform appearance.

d. Compacting

Compacting equipment shall produce the required compaction within the operation time limit.
Cement stabilized subbase/base shall be spread and compacted in only one layer according to the
provisions specified herein. Initial compaction shall follow the spreading operating immediately and
shall have at least one complete full coverage of the stabilised material.

When the finished surface after initial compaction is outside the tolerance specified hereinafter, all
high spots shall be trimmed off to within the specified tolerances. Filling of low areas by drifting or
hauling of trimmed material is prohibited.

Excess material may be placed as aggregate for shoulder construction or when directed by the
Engineer.

Excess material may also be used at other locations in the work, provided said excess material
complies with applicable specification requirements or shall be otherwise disposed of as permitted
by the Engineer.

Following such trimming, the finished surface shall be thoroughly compacted so that the entire layer
of cement stabilized subbase/base conforms to the compaction requirements hereinafter specified.
Final compaction shall be accomplished in such a manner that no loose material remains on the
surface and all tear marks are eliminated.

Relative compaction of cement stabilized subbase/base shall not be less than 98 % of the reference
design maximum dry density for the specified mixture.

Areas of the finished cement stabilized subbase/base which are of less thickness than as stated
above shall be removed and replaced with fresh mixture which complies with the requirements of
these specifications, all at the expense of the Contractor.

Surface shall be kept moist at all times for at least 7days or until such time as directed by the
Engineer.

Not more than 2 hours shall elapse between the time water is added to the aggregate and cement,
and the time of completion of initial compaction prior to trimming. Not more than 2½ hours shall
elapse between the time water is added to the aggregate and cement and the time completion of
final compaction after trimming.

f. Construction Joints

At the end of each day’s work and when cement stabilized subbase/base operations are delayed or
stopped for more than 2 hours a construction joint shall be made in thoroughly compacted material,
normal to the centre line of the roadbed, with a vertical face. Additional mixture shall not be placed
until the construction joint has been approved by the Engineer.

Where cement stabilized subbase/base has been finally compacted more than one hour, longitudinal
joints shall be constructed by cutting vertically into the existing edge. Material cut away may be
disposed of as specified for excess material. Face of the cut joints shall be moistened in advance
of placing the adjacent layer.

g. Curing

Completed cement stabilized subbase/base shall be covered with wet hessian cloth and watered so
as to keep moist at all time for at least 7 days or for the duration as directed by Engineer. Hessian
cloth shall be applied on the same day that final compaction is performed and as soon after said
compaction as is practicable.

No equipment or traffic will be permitted on the completed cement stabilized subbase/base during
the first 7 days unless otherwise permitted by the Engineer.

h. Surface Tolerances

At final compaction the finished surface of the cement stabilized upper subbase shall be uniform and
shall not deviate at any point more than 6 mm from the bottom of 3 m straightedge laid in any
direction.

Top of the layer shall not vary from the required elevation by more than 6 mm. All bumps and
depressions exceeding the specified tolerance shall be corrected by removing the defective work
and replacing it with new material as directed by the Engineer, all at the expense of the Contractor.

i. Thickness Requirements

Thickness of the completed cement stabilized subbase/base shall not vary more than 10 mm from
the thickness shown on the  Contract plans.  Sufficient measurements of thickness shall be taken
before and after compacting to establish the relationship between the thickness of the un-compacted
material and the completed work.  Thickness shall be controlled first by measurements taken of the
un-compacted  material.    When  the  measurements  indicate  that  an  area  will  not  be  within  the
allowable  tolerance  for  the  completed  work,  the  un-compacted  area  shall  be  corrected  while  the
material is still in workable condition.

Immediately after final compaction the thickness shall be measured at one or more points in each
300 m of the laid lane width of stabilised subbase/base layer.  Measurement shall be made by means
of test holes or other approved methods.  Points for measurement shall be selected by the Engineer
at random locations within each 300 m sections of the laid lane width in such a manner as to avoid
any regular pattern.  Various points on the cross section shall be covered.

Whenever a measurement indicates a variation from the thickness shown on the Contract plans of
more than the allowable tolerance, additional measurements shall be taken at intervals of
approximately 50 m until the measurements indicate the thickness is within the allowable tolerance.
Any area not within the allowable tolerance shall be corrected by removing the defective work and
replacing it with new material as directed by the Engineer all at the expense of the Contractor. Cutting

j. Compaction Control and Testing

Compaction of the cement stabilized subbase/base shall be controlled as the work progresses by
means of field density tests.

Field density tests shall be carried out immediately after compaction and before hardening of the
material in accordance with AASHTO T 191

or AASHTO T 205

or as directed by the Engineer.

Frequency of testing shall be 1 test every 100 lin. m of laid lane width. Field density of the compacted
cement stabilized subbase/base shall not be less than 98% of the reference design maximum dry
density.

k. Weather Limitation

Cement stabilized subbase/base shall not be mixed or placed when the atmospheric temperature is
over 30

C or when the weather is rainy.

Temperature requirements may be waived but only when so directed by the Engineer. When
temperature is higher than 30

C, particular care shall be exercised in order to minimize water

evaporation from the mixture.

In this case a test section shall be executed at the high temperature foreseen during the working
period in order to evaluate the water content necessary to compensate evaporation and to establish
actual setting time.

According to such test section the Engineer may order pre-moistening of aggregates before cement
mixing and watering of the granular subbase finished surface level.

However particular attention shall be paid to prevent shrinkage due to excess of water. Contractor
shall perform all tests required by the Engineer on said section at his own expenses.

Engineer will give approval of the test section not before 7 days from the completion of curing.

l. Trial Lengths for Cement Stabilized Upper Subbase

Prior to the commencement of the cement stabilized subbase/base operations, the Contractor shall
construct  trial  lengths  (not  to  exceed  250  m)  to  demonstrate  adequacy  plant  and  equipment  and
competence  in  performance  of  entire  operation  of  production  and  laying  and  compliance  to  the
specifications.

Design mix used in the trials shall be those approved for use as cement stabilized subbase/base
and the equipment used shall be that according to the Contractor's approved detailed programme of
work. Trial lengths shall not form part of the permanent works but may be permitted in the
construction of temporary detours of sufficient length.

Contractor may proceed with the cement stabilized subbase/base work only after the methods and
procedures established in the compaction trials have been approved by the Engineer.

3.2.5 Asphalt Treated Base

3.2.5.1 Description

Asphalt treated subbase and base courses shall be composed of mineral aggregates, mineral filler
and bitumen combined in an asphalt mixing plant.  Several mineral aggregates may be sized and
combined  in  such  proportions  that  the  resulting  blend  is  well-graded  and  is  within  the  specified
gradation  requirements.    Incorporation  of  mineral  filler  and/or  other  ingredients  shall  be  in  such
amounts as found appropriate to meet the required criteria and test limits specified and as instructed
by the Engineer.

Contractor shall furnish, place and compact a course of bituminous stabilized granular material
composed of mineral aggregates, mineral filler and bitumen combined in an asphalt mixing plant.

3.2.5.2 Materials

Unless otherwise indicated on the Contract plans, specified in the particular specifications, or
directed by the Engineer, all sand asphalt base shall comply with the requirements of asphalt treated
Type B as specified in Sub-article a of Article 3.2.5.2.

Materials used in asphalt treated subbase and base courses shall meet the requirements of the
following sub paragraphs of paragraph 4 of sub-article b of Article 3.3.2.5:

•

Fine Aggregate

•

Coarse Aggregate

•

Commercial Mineral Filler

•

Asphalt Binder

•

Hydrated Lime

a. Types of Asphalt Treated Subbase and Base Courses

Types of asphalt treated shall be as designated on the Contract plans or in the bills of quantities and
shall comply with the compositions as described below and as shown in Table 3-12.

1. Asphalt treated type A shall consist of natural or crushed mineral, aggregate, hydrated lime,

commercial mineral filler and bitumen combined to meet the specification requirements, and
shall be constructed to the thickness as indicated on the Contract plans. A minimum of 1.5
% hydrated lime by weight of total mineral aggregates shall be added in accordance with
Sub-article a of Article 3.3.3.1.

2. Asphalt treated type B shall consist of crushed coarse aggregate, natural and/or crushed fine

aggregate,  hydrated  lime,  commercial  mineral  filler  and  bitumen  combined  as  otherwise
specified and shall be constructed to the thickness as indicated on the  Contract plans.  A
minimum  of  1.5  %  hydrated  lime  by  weight  of  total  mineral  aggregate  shall  be  added  in
accordance  with  Sub-article  a  of  Article 3.3.3.1.   Fine  aggregate  portion shall  consist of  a
minimum of 25 % crushed sand.

3. Asphalt treated type C shall consist of natural or crushed mineral aggregates, commercial

mineral filler and bitumen combined to meet the requirements as otherwise specified and
shall be constructed to the thickness shown on the Contract plans.

Commercial mineral filler shall be used in all types of Asphalt treated mixes as necessary to meet
gradation and design criteria.

Minimum quantity of hydrated lime specified for type A and type B asphalt treated shall be increased
as necessary to meet design criteria.

b. Design Criteria

Laboratory test specimens of the asphalt treated mix shall be prepared and tested in accordance
with the procedures set forth for the Marshall method of mix design. Mix designs shall be checked
and approved by the Engineer prior to use.

Test requirements and criteria for asphalt treated mixes prepared as otherwise specified and as
indicated in Table 3-12.

Table 3-12: Asphalt treated mixes composition including hydrated lime & commercial

mineral filler as required

Standard sieve size

Percent passing by weight

Type A

Type B

Type C

25.0 mm

100

19.0 mm

95-100

9.5 mm

85-100

100

85-100

4.75 mm

85-100

2.36 mm

58-100

70-85

58-100

600 µm

22-74

38-56

22-74

300 µm

10-50

27-43

10-50

75 µm

4-12

Asphalt Binder percent by weight of total
mineral aggregate

5.0 - 8.0

Table 3-13: Design criteria for asphalt treated

Test

Type A

Min. - Max.

Type B

Min. - Max.

Type C

Min. - Max.

Marshall specimens (ASTM D1559)

Number of compaction blows, each end of

specimen

Stability, kg

200

175

150

Flow, 0.25 mm

8 - 20

Air voids, %

3 - 18

Immersion compression specimens (AASHTO T165)

Index of retained strength

requirement

c. Job mix Formula and Allowable Tolerances

All the provisions of Paragraph 2 of Sub-article b of Article 3.3.2.5 shall apply, except as specified
below for the maximum permissible ranges of tolerances:

•

Passing sieves 4.75 mm and larger

± 5.0 %

•

Passing sieves 2.36 mm, 600 µm and 300 µm

± 7.0 %

•

Passing sieve 75 µm

± 2.0 %

•

Asphalt Binder

± 0.4 %

d. Sampling and Testing of Asphalt Treated

Sampling and testing of asphalt treated shall be in accordance with the procedures set forth in
Paragraph 3 of Sub- article b of Article 3.3.2.5.

Contractor shall comply with all of the provisions of Section 3.3.3 with respect to asphalt treated,
subject to the following modifications and additions:

1. Preparation and handling of mineral aggregates: Moisture content of the heated and dried

aggregate shall not exceed 1.0 %. If the Engineer so requires, the angle of the drier shall be
reduced to such a position as to hold material in the drier for a longer period of time for
optimum condition of heating and drying.

2. Proportioning and mixing: Heated ingredients shall be combined in such a manner as to

produce a mixture which when emptied from the mixer shall have a temperature of between
107° C and 149° C. Temperature of the aggregate immediately prior to mixing shall be within
± 7.0°C of the temperature of the Asphalt Binder and the temperature of the aggregate and
asphalt prior to mixing shall be approximately that of the completed mix as defined in the job
mix formula approved by the Engineer. Mix temperature shall be within the allowable
tolerance set out in the job mix formula when emptied from the mixer but in no case shall
exceed 149° C. Filler shall be proportioned into the mixer with the aggregate in the quantities
specified in the job mix formula, all as approved by the Engineer.

3. Delivery of the mix: Mix shall be delivered to the job site at a temperature between 80° C and

149° C and shall in all cases comply with the temperature and with the permissible variation
thereof set out in the job mix formula for mix temperature on delivery to the job site.

4. Spreading of the mix: Asphalt treated subbase and base courses shall be laid in maximum

50 mm layers. Thinner layers shall be used if excessive shoving, etc., occurs. Any additional
layers shall be placed as soon as practicable after the first layer has been executed to the
required grade, line, cross-section and density; finished, rolled and cooled; and after the tack
coat, if required, has been applied in accordance with requirements of these specifications.

5. Compaction of the mix: Mix temperature shall not be allowed to drop below 74° C prior to

initial breakdown rolling. Tapered edges against which no additional layer is to be placed,
shall be carefully rolled along the entire length of the edges.

a. Testing and Acceptance of Asphalt Treated Subbase and Base Courses

All of the provisions of Paragraph 3 of Sub-article b of Article 3.3.2.5 shall be applicable to asphalt
treated subject to the modifications and additions included herein.

1. Requirements for compaction of asphalt treated: Minimum degree of compaction for asphalt

treated mixes shall be 95 % of the laboratory Marshall specimen prepared in accordance with
the job mix formula.

2. Thickness requirements:

i. Total constructed thickness of asphalt treated subbase or base course used for new

construction, reconstruction or roadway widening shall not vary more than 8 mm from
the total thickness shown on the Contract plans.

ii. In the event the constructed thickness of the asphalt treated subbase or base course

is 8 mm more than the total thickness shown on the Contract plans, the area shall be
corrected as directed by the Engineer by removing the excess material in an approved
manner to provide the required thickness.

iii. In the event the constructed thickness of the asphalt treated subbase or base course

is 8 mm less than the total thickness indicated on the Contract plans, the Contractor
shall provide additional material in the next course (base course or wearing course). In
no case shall the deficiency of the subbase or base course exceed 25 mm.

iv. Asphalt treated subbase or base course shall be constructed to the grade level as

shown on the Contract plans, as specified and as approved by the Engineer.

wearing course be less than the total sum thickness of all courses as indicated on the
Contract plans.

3. Requirements for evenness of surface and grade level: Final surfaces of the subbase or

base  courses  shall  be  tested  by  means  of  a  5  m  long  straight  edge;  and  no  rises  or
depressions in excess of 10 mm shall appear on the surface; otherwise such areas shall be
stripped,  corrected  and  recompacted  to  comply  with  all  specification  requirements  and  as
approved by the Engineer.  Further, the finished surface of the subbase or base course shall
be constructed to within 12 mm of the grade levels shown on the Contract plans.

b. Equipment Used for Asphalt Treated Subbase and Base Courses

Provisions of 3.3.3.1, of shall be adhered to, subject to the following modifications and additions:

1. Screens for asphalt mixing plants: Asphalt mixing plant shall be equipped with screens

suitable for screening the aggregate into sizes such that they may be recombined into a
gradation meeting the requirements of the job mix formula. However, if the nature of the
aggregate, in the opinion of the Engineer, is such that no screening is required by reason of
its satisfactory natural gradation, then the plant may be equipped with a scalping screen of a
size suitable to remove oversize aggregates and other deleterious material.

2. Rollers: Rolling equipment shall consist of steel-wheeled rollers and pneumatic-tired rollers

as specified in Sub-article c of Article 3.3.3.1.  A minimum of three rollers shall be required
at  all  times:    one  self-propelled  pneumatic-tired  and  two  steel-wheeled  rollers.    As  many
additional  rollers  shall  be  used  as  necessary  to  provide  the  specified  density  and  surface
characteristics  in  any  orderly,  efficient  and  continuous  manner.    Tandem  steel-wheeled
rollers shall be of such weight that, under working conditions, will develop contact pressure
adequate to obtain the required density.

3. Unacceptable equipment: Engineer will have the right to stop the use of any equipment or

plant which he deems to be inferior to the quality required and to instruct the removal of such
equipment and to have it replaced by suitable equipment or to alter the method of operation
at any time.  Contractor shall immediately comply with such instructions without being entitled
to  any  indemnities  or  extensions  as  a  result  of  such  instructions.  Contractor  shall  not  be
allowed to use any equipment or plant before obtaining the approval of the Engineer, and the
Contractor  shall  undertake  to  follow  sound  technical  methods  of  operation  and  to  engage
skilled and trained operators, mechanics and labor to carry out the works.  Engineer will have
the  right  to  expel  any  operators,  mechanics  or  labor  and  to  instruct  suitable  replacement
thereof at any time he deems such action is necessary.

3.2.6 Lime Stabilized Subbase/Base

3.2.6.1 Description

Lime stabilized subbase/base shall consist of material aggregate uniformly mixed with lime and
water, placed and compacted in one single layer on a prepared granular subbase in conformity with
the Contract plans and this specifications or as established by the Engineer. Thickness and width
of the lime stabilized subbase/ base layer shall be as shown on the Contract plans.

3.2.6.2 Materials

Furnish  uncontaminated  materials  of  uniform  quality  that  meet  the requirements  of  the  plans  and
specifications.  Notify  the  Engineer  of  the  proposed  material  sources  and  of  changes  to  material
sources.  Obtain  verification  from  the  Engineer  that  the  specification  requirements  are  met  before
using  the  sources.  The  Engineer  may  sample  and  test  project  materials  at  any  time  before
compaction.

a. Lime

Furnish lime that meets the requirements of AASHTO M 216 for hydrated lime, or AASHTO T 27
and AASHTO T 219 for quicklime. When furnishing quicklime, provide it in bulk.

b. Aggregate Material

Furnish aggregate material that meets the requirements “granular base or subbase course” for the
type and grade shown on the plans, before the addition of lime. At least one sample from each stock
pile every 1000 m3 shall be taken for abrasion, sand equivalent, plasticity index and grading

c. Water

d. Asphalt emulsion

When asphalt emulsion is permitted for curing purposes, furnish materials that meet the
requirements Bituminous Prime Coat, as shown on the plans or as directed.

e. Job Mix

At least 30 days prior to the date the Contractor intends to begin construction of the lime stabilized
base/subbase, and after receiving approval of the aggregates from the Engineer and after the
delivery on site of the lime specified for this work, the Contractor shall make written request for the
approved job-mix formula from the Engineer. Job-mix formula will be prepared by the Contractor,
and will be tested by the Engineer.

1. Mix Design

The steps for lime stabilization mix design are:

•

Add the appropriate target percentages of lime (generally starting with 1 percent by weight

of the entire mixture and increasing in 1 percent increments to 4 percent),

•

Determine moisture density relationships for each aggregate-lime blend following either

AASHTO T-99 or AASHTO T-180.

•

Determine CBR (AASHTO T193) of the lime-aggregate blends following curing for 7-days

at 40°C. CBR of the blind material shall not be less than 60% @ 98% MDD.

f. Storage and Handling of Materials

Store quicklime and dry hydrated lime in closed, weatherproof containers.

3.2.6.3 Equipment

Equipment shall be according to the type and number outline in the Contractor’s detailed programme
of works, as approved by the Engineer. All equipment, tools, and machinery must be maintained in
a satisfactory working condition.

If the lime will be Road mixed, pulverization equipment should be used. Otherwise mixing plant and
spreader equipment are used for plant mixed.

a. Pulverization Equipment

Provide pulverization equipment that:

•

cuts and pulverizes material uniformly to the proper depth with cutters that plane to a uniform

surface over the entire width of the cut,

•

provides a visible indication of the depth of cut at all times, and

Uniformly mixes the materials.

b. Mixing Plant

Provide a stationary pugmill that uniformly mixes lime, water, and base material in the specified
proportions. Obtain approval before providing weigh-batch or continuous mixers. Equip plants with
automatic proportioning and metering devices.

c. Spreader Equipment

When shown on the plans, provide equipment that will spread the lime-treated mixture in a uniform
layer in 1 pass. When shown on the plans, equip spreaders with electronic grade controls.

3.2.6.4 Construction

Construct each layer uniformly, free of loose or segregated areas, and with the required density and
moisture content. Provide a smooth surface that conforms to the typical sections, lines, and grades
shown on the plans or as directed.

a. Preparation of Subgrade

Top surface of subgrade ready to receive lime stabilized subbase, (immediately prior to spreading)
shall conform to the compaction and elevation tolerance otherwise specified, and shall be free of
loose or extraneous material.

In hot weather, the top surface of subgrade shall be moistened before spreading of the lime stabilized
subbase, in order to prevent evaporation.

b. Site Mixed

1. Pulverization

Pulverize or scarify existing material after shaping so that 100% passes a 37.5 mm sieve. If
the material cannot be uniformly processed to the required depth in a single pass, excavate
and windrow the material to expose a secondary grade to achieve processing to plan depth.

2. Application of Lime

Uniformly apply lime using dry or slurry placement as shown on the plans or as directed. Add
lime at the percentage determined “Mix Design.” Apply lime only on an area where mixing
can be completed during the same working day.

Minimize dust and scattering of lime by wind. Do not apply lime when wind conditions, in the
opinion of the Engineer, cause blowing lime to become dangerous to traffic or objectionable
to adjacent property owners. When pebble grade quicklime is placed dry, mix the material
and lime thoroughly at the time of lime application. Use of quicklime can be dangerous. Inform
users of the recommended precautions for handling and storage.

Before  applying  lime,  bring  the  prepared  roadway  to  approximately  optimum  moisture
content.  Distribute  the  required  quantity  of  hydrated  lime  or  pebble  grade  quicklime  with
approved  equipment.  Only  hydrated  lime  may  be  distributed  by  bag.  Do  not  use  a  motor
grader to spread hydrated lime.

3. Mixing

Begin mixing within 6 hours of application of lime. Hydrated lime exposed to the open air for
6 hours or more between application and mixing will not be acceptable.

Thoroughly mix the material and lime using approved equipment. Allow the mixture to mellow
for 1 to 4 days, as directed. When pebble grade quicklime is used, allow the mixture to mellow
for 2 to 4 days, as directed. Sprinkle the treated materials during the mixing and mellowing

Abu Dhabi, United Arab Emirates. STANDARD CONSTRUCTION SPECIFICATIONS (PART 1 - ROADS, Second Edition 2020) - page 23