Construction Methodology of Wet Mix Macadam
1.
NAME OF
ACTIVITY:
WMM Laying.
2. Highway
Activities
3. REFERENCES:
a) Ref. to Technical Specification
(MORT&H Spec. & Amendments)
a.1) Section: 406
a.2) Tables: 400-12, 400-13, 900-1 and 900-3.
b) Ref. other related works prior to this
activity:
b.1) Granular sub base top layer, level
Recording, Stock Approval.
c) Ref. to Drawing(s):
c.1) Nil
d) IS/IRC Specifications
d.1) Nil
4. SCOPE OF WORK:
The
work shall consist of laying and compacting well graded aggregate &
granular material premixed with water on prepared granular sub-base for
widening/new construction of carriageway, hard shoulders and service roads. The
thickness of a single compacted wet mix macadam layer shall be 125 mm.
5. EQUIPMENT/MACHINERY REQUIREMENT:
WMM
plant – pug mill- 01 Nos.
Wheel
loader- 01 Nos.
Tipper- 06 Nos.
Sensor
paver- 01 Nos.
Water
tanker- 01 Nos.
Vibratory
roller- 01
Nos.
Straight edge- 01 Nos.
Survey equipments- 01
Nos.
String wire and peg set- 200 mtr (wire)
6. Stand by Equipments:
Motor grader- 01 Nos.
Tipper- 02 Nos.
Vibratory roller- 01 Nos.
7. MATERIAL:
Physical requirements:
The
aggregate shall be produced from the multiple stage crushing and screening
plant. The aggregate for WMM shall confirm to the grading given in Table 400-13.
|
IS Sieve
designation
|
% by weight
passing the IS sieve
|
|
53.0mm
|
100
|
|
45.0mm
|
95-100
|
|
22.4mm
|
60-80
|
|
11.2mm
|
40-60
|
|
4.75mm
|
25-40
|
|
2.36mm
|
15-30
|
|
600mic
|
8-22
|
|
75mic
|
0-5
|
The
material to be used shall have a Los Angeles abrasion value not more than 40%
or Aggregate Impact Value not more than 30%, combined flakiness and elongation
indices not more than 35%, PI value not more than 6% and if water absorption is
more than 2% soundness test shall be carried out.
8.
PROCEDURE FOR CONSTRUCTION
Wet
mix macadam shall be prepared in approved mixing plant of suitable capacity of
pug mill. Optimum moisture shall be determined in accordance with IS: 2720
(Part-8), due allowance shall be given for evaporation losses at the compaction
it shall not vary 1% above to 2% below OMC.
Immediately
after mixing it shall be transported to laying site by tippers and shall be
spread uniformly and evenly upon the prepared granular sub-base by a paver finisher
with electronic/Motor grader. However at the time of spreading the surface
shall be checked for grade, camber and thickness with templates and high or low
spots are to be rectified by removing or adding new materials.
The
mix shall be laid so that a each layer of 125 mm maximum thickness is achieved
after compaction. The compaction shall be done with 80 to 100kN minimum
capacity static weight vibratory rollers at a speed not exceeding 5KM/hour.
The
compaction shall progress from the lower edge towards the upper edge, and each
pass shall overlap 1/3rd the preceding pass. The places not accessible to the
roller shall be compacted with mechanical tampers or by a plate compactor.
Rolling
shall be continued till such time that achieves 98% of MDD. After final
compaction the surface allowed to dry for 24hours, and no vehicular traffic
should be allowed till the weathering course lay.
Where
the surface irregularities exceeds the permissible limits or defective due to
sub grade soil getting mixed with aggregates, the full thickness of layer in
the affected area to be removed and replaced by fresh material and compacted.
Field
dry density will be carried out by sand replacement method and recorded.
The
surface finish of construction shall conform to MORT&H 902.
During
the period of construction arrangement of traffic shall be in accordance with
MORT&H 112.
9. Trial Patch Laying
Trail patch will be carried out on prepared GSB layer of 100 m length
double land
width. In order to establish the number of passes of vibratory roller to
obtained the
required density for 125mm thick WMM layer.
10. FOR QUALITY ASSURANCE:
Sample
collect at site and following test in site laboratory as per clause 900 of
MORT&H.
i) Gradation
& atterberg limit : - One
test every 200 cum.
ii) AIV : - One test every 1000 cum (As per IS 2386-part 4)
iii) FI
& EI : - One test per 500 cum of aggregate.
(As per IS
2386-part 4)
iv)
Density : - One test of three test per 1000 sqm.
v) Optimum Moisture Content
11. Lateral
Confinement:-
As the shoulder and back fill material
are of different type therefore according to MORT&H specification Clause 406.3.2 and
filling in shoulder shall be commence simultaneous and compaction will be first
at pavement layer i.e. WMM layer then after adjoining layer.
12. Procedure
a)
Work shall commence on site upon approval and
acceptance of the sub base layer (GSB).
b)
Check whether GSB lays compaction is in fact if there
is a considerable time delay (say 10 days) in laying of WMM.
c)
Shoulder shall be laid & compacted for confinement
of WMM layer to be laid.
d)
The WMM shall be plant mix with moisture content within
reasonable limits of the optimum moisture content as determined in field
laboratory in accordance with IS-2720(Part-8).
e)
The approved Wet Mix Macadam shall be delivered to site
by the Tipper/truck to prevent the loss of moisture the material shall be
covered if necessary as per weather condition.
f)
The WMM shall be laid using a Paver finisher with
electronic sensing device/grader (as per MORT&H clause 406.3.4).
g)
Segregation at localized areas shall be made good by
back casting with fines or by immediate removal and replacement of the freshly
laid Wet Mix Macadam.
h)
Transverse joints shall be lapped and longitudinal
joints due to stoppage of work will have the loose removed before paving
resumes.
i)
Compaction shall be carried out using vibratory roller
and as per specification Rolling always commence from lower side to upper side
with sufficient number of passes as decided in Trial Patch. Rollers shall move
with speed not more than 5km/hr speed.
j)
The surface of WMM shall be finished to the grade and
line as per required by the drawings and with in specific tolerance limit as
per Clause 902 of MORT&H specification.
k)
Completion of laying and compaction approval of
Engineer will be obtained for compliance with the specific requirement before
proceeding with the next layer.
l)
Sampling of mixed material shall be carried out at
plant or site to determine the gradation and moisture content.
m)
Top surface of 2nd layer WMM shall be check
on grid level longitudinal at 10m interval in straight and at 5.0 m interval in
case of super elevation; and transverse 0.5m from pavement centre line and edge
of pavement and centre of L/R carriageway.
13. MANPOWER REQUIREMENT:
1. Section In charge
2. Site In charge
3. Section Engineer
4. Site Supervisor
14. MACHINERY REQUIREMENT:
·
WMM Plant
·
Tractor Dozer
·
Wheel loader
·
Motor Grader
·
Paver finisher with electronic sensing device.
·
Vibratory roller of 8T and 10T
·
Tipper truck 7cum/14cum
·
Water tanker with sprinkler (Tractor mounted or
truck mounted)
15.
MEASUREMENT FOR PAYMENT:
WMM layer shall
be measured as finished work in position and it shall be paid as per BOQ item
No.3.02.
16. SAFETY AND ENVIRONMENTAL ACTIVITIES :
a)
Caution Boards will be placed at the beginning and end
of working site and also at risky locations.
b)
Signal man will be placed at heavy traffic locations at
the time of Execution.
c)
Reflective sign boards will be placed during night near
risky locations.
d)
All necessary measures shall be taken to control the
disposal of all forms of waste generated by the construction operations and in
all associated activities.
e)
All necessary measures and precautions shall be taken
to avoid any nuisance or disturbance arising from the execution of the work.
17. Site Records
Record of WMM shall as follows:-
- Date of laying
- Source of Material
- Weather report
- Machinery list/ Manpower used at site and period worked.
- Location and length of work (chainage) and width of layer.
- Test result of gradation (moisture content and field density after compaction)
- Level Check record with respect of design level showing deviation in design and achieve level with thickness of laid layer.
- Reasons for delay or obstruction of any.
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