Pothole - Method Statement

7/29/2019 Pothole - Method Statement

1/5

1.3.5 Earthworks

Any service utilities identified within the work area will be relocation as may be required

and as will be instructed by the Engineer. The works will then be set out as per approvedcross sections using acceptable survey methods and practices. The existing ground will

then be compacted to specifications after removing soft material from soft spots which

shall be repaired with approved fill materials.

The major earthworks will be for the widening of shoulders to achieve the 1.5m widths

both sides. Before this, trimming and ripping of bituminous materials and carting to spoil

will be done. The shoulders will be benched and backfilled where necessary withselected fill material obtained from approved borrow pits.

Cutting wherever required shall be done to proper line and grade. Step construction will

be carried out per layer at the joint where excavating both vertically and perpendicular tothe direction of the travel. The step will be 500mm perpendicular to the direction of travel

and 150mm vertical unless otherwise instructed by the engineer. The cut surface willthen be compacted to receive fill material.

The material from cutting done to achieve benches, if approved, will be used for fill andcompacted as per specifications. Surplus or unsuitable materials will be carted to

designated spoil areas. Additional fill material will be obtained from borrow pits. Fill

materials from identified sources shall be tested for compliance with contractrequirements. The test reports shall be submitted to the Engineer for approval as per

agreed procedures. The fills shall be compacted in approved layers. The layers of fill will

not exceed 150mm and filling will be carried out up to bottom of the sub base. Aftereach layer has been tested and approved, a new layer shall be started till required levels

are reached. The same procedure shall be followed for each layer.

The processing of sub grade will be carried out at this stage as well.

1.3.6. Shoulders and PavementThe construction works for the shoulders and pavement will involve both repairs and

complete reconstructions of some sections.

1.3.6.1.Repairs

(a) Repairs to potholed areas

Before repairs to potholed areas are executed, the trimming edge will be marked out with

white paint. To enable compaction by a pedestrian roller, the trimmed area will be at least1.5mx1.5m. The potholed areas will then be trimmed and excavated to the sizes and

shapes determined in the design.


2/5

The excavated material will be carted to spoil and the surface watered and compacted toreceive cement improved sub base or base depending on the extent of the repairs. The

added material will then be compacted

Part to be trimmed

Pothole

Trimming edge

The excavated pothole will then be filled with cement-stabilized gravel for sub base andbase and compacted as directed by the Engineer. The approved base layer will then be

primed with MC 30 before laying asphaltic concrete type II with K1 60 as tack coat.

(b) Repairs to Surface/Edge Failures

The location of surface/edge failures will be determined during the survey and designstage of works execution. Surface failures in form of cracks will be cleaned and sealed.

The entire crack area will be cleaned by brushing with a wire brush and then blowing

with a compressed air jet to remove foreign matter. Sealing will involve applying80/100-penetration grade bitumen using a pouring pot or pressure lance and hand

squeegee, and surface dusted with 0/6 mm aggregates. The requirements of section

1501A of the special specification will be taken into consideration.

Surface failures in form of depressions will be regulated with AC type I just beforesurface dressing. The existing road surface levels will be taken and compared with the

design levels to obtain the estimated quantity of AC type I to be added on the surface.

The surface will be cleaned before manually laying the regulating layer. The edgefailures will be will be repaired with AC Type II as will be directed by the Engineer.

This will be placed manually after the surface is cleaned and any non bituminous surfaces

primed with MC 30.

(c) Repairs to existing sub base or base

The failed sub base or base at isolated areas will be repaired with cement-stabilizedgravel. The surface will be scarified, watered, cement-stabilized gravel added, processedand compacted. It will then be primed with MC 30 on the base. The primed surface will

then be sprayed with K1-60 as tack coat and surfaced with AC Type II.

1.3.6.2 Complete base reconstructionThe complete reconstruction will start from the road base. The existing bituminous

surface including any contaminated base material will be ripped and carted to spoil. Theexisting base material will then be scarified and processed to a depth of 100mm. Base


3/5

quality cement improved gravel will be added to achieve a compacted thickness of150mm to form the base layer. This operation will be extended to the shoulders, which

will be benched and backfilled to widen then to 1.5m, both sides. The gravel to be cement

improved will be imported and tipped as per tipping schedule predetermined for the rightthickness of the layer. The determined cement quantities are added and mixed with the

gravel in situ using a reclaimer.

The survey poles set out with final road level markings and offsets by the surveyor will

guide the construction process. After checking of levels, the cement improved base shall

be pre-shaped to around 0mm above the final compacted level and water sprayed to bring

the moisture content to around designed optimum level. The water shall be evenlydistributed through out the layer by grader blade. Compaction shall then commence by

the Vibratory roller moving parallel to the road but working from outside towards the

central line of the road. The whole operation, from opening of cement pockets to final

compaction by pneumatic tyred roller (PTR) shall be completed in less than 8 hours.Curing of the layer shall commence shortly after. The layer is then tested for compliance

with specifications.

The compacted base layer will have its levels checked. The grader will be used to trimoff high points on the surface to final level and a tandem roller will continue to roll till

mechanically stable crack free surface is obtained. The density of the layer will be

checked using appropriate instruments like a nuclear density gauge or by the sandreplacement method. The surface will be processed and compacted to 95% MDD.

1.3.6.3 Priming with MC 30The approved base layer will be primed with MC 30 at a rate between 0.8-1.21/m

2. The

priming will be done in accordance to Clauses 1502 of the Special Specifications and

1504A-1507A and 1503B-1505B of the Standard Specifications.

The approved surface to be sprayed with MC 30 will be thoroughly cleaned by sweeping

with mechanical brooms or other approved means. The surface will be checked for line,

camber and level.

Immediately prior to the application of prime coat, the surface of the layer will be slightly

sprayed with water to give complete coverage of the layer unless otherwise instructed ythe Engineer. The surface will not be saturated with water. Any water on the surfaceshall be allowed to drain off before the prime coat is applied.

The MC 30 prime coat will be sprayed from a pressure distributor. The distributor hasnozzles arranged to give uniform spray. The distributor will be tested prior to spraying

discharging on suitable material such as building paper. Before spraying, all kerbs, road

furniture etc that may be disfigured by splashing of bitumen shall be protected.


4/5

The prime coat will be cured and blinding provided as may be necessary in accordance toclause 1505B of the standard specifications.

Finishing, joints and edges will be carried according to clause 1611A of the special

specifications.

During mixing and laying of the asphalt, control test on the constituents and on the mixed

material will be carried out in accordance with Clause 1612A and section 3 of the special

specification.

1.3.6.5 Surface dressing

Finally, a double seal surface dressing of 14/20mm and 6/10mm pre-coated chippingswill be provided for the whole carriageway. The surface dressing will be done in

accordance to sections 1502C to 1505C of the special specification.

The bitumen spray rates will be 1-1.41m2

for the first seal and 0.5-0.81/m2

for second

seal. The 14/20mm size pre-coated chippings will be spread at a rate between 60-90

square metres per cubic metre. The 10/14 mm size pre-coated chippings will be spread ata rate between 70-120 square metres per cubic metre while 6/0mm size pre-coated

chippings will be spread at a rate of 70 120 square metres per cubic metre. The actual

spray and spread rates will be obtained from trail sections done in the presence of theEngineer and the Chief Materials Engineer or their representatives.

The surface for surface dressing will be cleaned of all foreign matter by brushing

thoroughly with a mechanical broom or any other method as will be approved by the

Engineer. All defects will be made good to the approval of the Engineer.

The bitumen will be transported to site in the distributor while the aggregates will be

transported on tippers to be tipped into the chips spreader as the surface dressing

progresses.

As soon as possible after the surface is prepared and approved, the binder will be sprayeduniformly by a distributor at the specified rate within 12 hours. The spraying width willbe normally one lane to allow passage of traffic. Immediately after the binder has been

sprayed, clean dry chippings shall be applied uniformly at the specified rates by

mechanical chip spreader to match the rate of bitumen spraying.

Rolling will begin immediately after the chippings have been spread. This will be within

two minutes of the application of the binder.


5/5

The road will be opened to traffic when the binder will have attained sufficient viscosityto prevent the stones from being wiped off. Temporary restriction signs, barriers and

removable bumps will be erected as instructed by the Engineer. Vehicle speeds on the

newly laid surface will be restricted to 30km/h.

The correct rate of spread will be assessed visually, as providing complete coverage, with

the film binder still visible between the chippings. Tests will be done to confirmcompliance to the specified spray and spread rates.

1.4 Drainage and Protection works

Improvement of the drainage system will include excavating, grading and shaping

existing side drains, mitre drains and catch water drains etc to free flowing condition andcarting away all grass and deleterious materials to spoil. De silting and unblocking of

cross and access culverts will be done. Defective existing culverts will be removed.

1.6 Passage of Traffic

Traffic management will be done continuously throughout the construction period to

ensure safe passage of traffic through the works. At locations of complete roadreconstructions, 6m wide deviations with gravel wearing course of 150mm thickness and

CBR greater then 20 will be provided. On stream crossings, a special solution will be

developed for each location as dictated by the site conditions.

At locations of road repairs, flags men equipped with two way radios will be provided todirect traffic. In addition warning signs, temporary restriction signs, advance warning

signs, barriers and temporary bumps will be provided where necessary. We will in

addition liaise with the traffic police and other government officials of the area on trafficcontrol and other matters.

The road ahead of the works will also be maintained using gravel of base quality as will

be directed by the Engineer.

Documents

Pothole - Method Statement