ROAD WORKS - PROCEDURE, METHODOLOGY, TESTS & CHECKLISTS

Road works involve the process of strengthening the earth's surface suitably to enable easy movement of human and vehicular traffic over it.

IMPORTANT TERMINOLOGY

Road/ Pavement             

It is a hard and even surface, for the smooth movement of vehicles, pedestrians, bicycles, etc.

Carriageway

The portion of the roadway that is designed and constructed to take vehicular traffic.

Shoulder or haunch or berm 

It is the portion of the road that is immediately beyond the edges of a carriageway which can be used by vehicles occasionally to pull over for short intervals or while crossing each other from opposite directions. 

Median 

The two carriageways of a road are separated by a strip of land along the road called as the median. The median can be used to fix streetlights, drains and also to create green areas. 

Kerb stones 

A hard stone, like granite, or pre-cast concrete member, of suitable dimensions, used to border a road, limiting the footway are called as kerb stone. 

Camber 

The slight convexity on the surface of a road is called camber. It is given to drain the water off the road during rains. A minimum camber of 2.5% is required for any road.

Sub grade

The under lying layer of the road, upon which the pavement structure is built is called as sub grade.

Wet Mix Macadam (WMM)

It is granular material for sub-base bound by water. It is essentially an

aggregate material of specific grading.

Water Bound Macadam (WBM)

It is a tightly bound, strong and semi-pervious surface. Water bound macadam (WBM) comprises two components, a layer of coarse stone (37.5mm to 75mm size) into which graded fine aggregate (5mm size) is slurried or washed. It can be used as an unpaved surface or as a base material on roads with bituminous seals.

Bituminous Macadam (BM)

One or more layers of well graded aggregates, sized between 0mm to 40mm, each layer bound by bitumen is called as bituminous macadam.

Granular Sub Base (GSB)

It is a layer of selected material such as moorum, gravel, laterite, etc, over the prepared sub grade in layers of designed thickness.

DBM

Dense Bituminous Macadam.

Asphalt concrete             

It is a premix of bitumen, sand and mineral aggregate (larger than sand size), with or without a filler material in prescribed proportion.

Asphalt concrete base course (tack coat)

One or more layers of asphaltic concrete of specific design given on top of the Dense Bituminous Macadam (DBM).

Cut and fill

It is the process of excavation (cut) or raising the natural ground level (fill) by depositing suitable material in a prescribed way, to achieve a desired formation level is called as cut and fill.

Culvert

A sewer or drain crossing under a road or embankment.

CBR

California Bearing Ratio.

ROW

Right Of Way. It is a path or strip of land over which someone has the legal right to pass.

PROCEDURE

Before construction:

•              All the necessary latest GFC drawings and complete specification details like alignment of the road, width of carriageway, kerbs, drains, shoulders, camber etc. should be available.

•              Proper inspections chambers should be planned and provided for the sewage lines at         suitable locations.

•              Any necessary cutting with respect to the level of the roads should be done.

•              All unsuitable excavated material (especially black cotton soil) has to be disposed away at a suitably approved dumping site. However, fertile soil can be stocked suitably and can be used for landscaping along the sides or on the median of the roads.

•              The entire area along which the road shall be aligned should be cleaned of any debris, rocks and vegetation.

•              Trees shall be transplanted and loss of vegetation should be minimized.

•              The soil test reports should be available at site.

•              Before proceeding with the construction of the road section, the underlying sub grade has to be compacted and tested to ensure the strength as per specifications given by the consultant.

During construction:

•              The proposed road areas have to be surveyed to establish the     of the road 

sections according to the GFC drawings.

•              As per drawing, establish bench mark pillars along the length of the road on either sides at intervals of 5 to 10m.

•              The sub-grade is prepared by cutting/ filling (embankment) to the required level.

•              The underlying cut areas have to be scarified and then given the rough profile of the road during the compaction process using a single drum roller. 98% of the maximum dry density of the soil should be the achieved compaction and a minimum of 8% CBR.

•              The density of the compacted soil has to be checked by using sand replacement method or by using a nuclear gauge. This compacted soil should be able to take up the loads as per design.

•              Usually, after the sub grade work is finished, all the underground utilities, ducts, culverts, etc shall be installed.

•              Electrical, sewage/ water line, which cross the alignment of the road, should be completed as per requirement. The water lines should be above the sewage lines.

•              Sub grade material shall be placed where ever required and compacted in layers not exceeding 150mm (after compaction), to the desired level, to achieve the required compaction.

•              A layer of Granular Sub Base (GSB) shall be laid in a maximum thickness of 150mm (after compaction) per layer and compacted to the required level.

•              After spreading the granular sub base, it shall be watered and rolled to achieve the desired compaction using a single drum vibratory roller.

•              The aggregates shall be slightly wet during this process — say 5% to 7% moisture content.

•              While laying the granular sub-base, the camber and profile of the road has to be maintained as per the GFC drawings.

•              Upon the completion of the GSB layer, gutters shall be installed to line and level as per the GFC drawings, before laying the wet mix macadam.

Wet Mix Macadam (WMM) consisting of graded and granular material which is premixed with water, is laid in one or more layers not exceeding 150mm each (after compaction), leveled with a grader 0 and then compacted with a vibrating soil compactor.

•              The top of this layer should have the profile and slope as per GFC drawings.

•              On the complete layer of wet mix macadam, prime coat shall be applied using a bitumen sprayer at the rate of 0.8 — 1.2 liter/ m2  .

•              If cut back bitumen is being used to prepare the primer, then a curing period of 24 hours is mandatory before laying the DBM.

•              If a bituminous emulsion is being used as a primer, then DBM works can successively continue.

•              Then bitumen is heated to 180°C and mixed with well-graded aggregates of size 20mm in a bituminous concrete batching plant to get DBM. The mix should be as per design from the structural consultant.

•              DBM is transported in dumpers and fed into the paver machine.

•              The paver machine will lay the DBM to the required thickness, level, alignment and width as per the GFC drawings.

•              The temperature of the asphalt base course at the time of laying and rolling by the paver machine should not be less than 120°C. 

•              Double drum vibratory rollers are then used to further compact and is finished using a pneumatic roller.

•              Above this asphalt base course, a layer of tack coat (at the rate of 0.4 — 0.6 liter/ m2) is sprayed with a bitumen sprayer.

•              The asphaltic concrete wearing course is then laid using a paver machine and rolled with double drum vibratory rollers. This is also called as the seal coat. The design mix of the wearing course shall be as per approved specifications.

•              A pneumatic roller is used for the compaction of this layer.

•              No vehicular traffic should be allowed on the freshly laid road for a minimum of 12 hours.

After construction

•              Upon completion of the road construction, the pavement marking, fixing of road signs, markers, reflectors, convex mirrors, painting of kerb stones, etc should be completed.

•              The walking area next to the road has to be built as per design.

•              Poles for street lights, signals and other signages should be installed and all electrical works should be completed.

       All the storm water lines, sewer lines and other utilities shall be tied to their corresponding main lines at suitable locations as given in the drawings.

Installation of kerb/ gutters

•              Prior to the start of the kerb/ gutter installation, all underground utility crossings, drains and ducts should be completed.

•              The granular sub-base layer should be completed.

•              The top of the kerb stone should be at a height of 150mm above the top of the finished road

level.

•              PCC base shall be cast in place along the line of the kerb to the required width.

•              The kerb stones are fixed on this PCC layer, using cement mortar 1:5.

•              String line should be used to ensure exact alignment of the kerbstones along the length of the road.

•              A gap of 3 to 5mm should be maintained between any two consecutive kerbstones.

•              A minimum of 7 days curing should be done.

Interlocking paver fixing

Interlocking pavers are pre-cast concrete elements that can be used for both walk ways and for vehicular traffic.

After fixing, each paver becomes integrated to form the pavement because of the interlocking

system and hence have high load carrying capacity. The finished surface provides good grip for vehicles. The interlocking pavers can be of different colours and shapes.

•              The area where the interlocking pavers have to be installed shall be well compacted using vibratory rollers or earth rammers to achieve desired compaction.

•              A layer of sand/ crushed sand shall be laid and compacted to a thickness of 40 to 50mm.

•              The interlocking pavers are then laid in a pattern as per design.

•              The interlocking pavers shall be fitted and secured in place using a rubber hammer to the required level.

•              All the closure gaps at the edges and corners shall be fitted with cut pieces of right sizes.

•              All the joints between the pavers shall be packed with sand to fill all gaps.

•              The top of the interlocking pavers shall be flooded with water to ensure proper packing.

QUALITY INSPECTION METHODOLOGY

•              The top level of different layers has to be checked and should be as per design.

•              Check the camber given to the road and the slope of the banking given at curves.

•              The aggregates used shall be well graded and should fall within the

prescribed size.

•              The temperature of the asphalt base course during laying should not fall below 120°C

•              Check the thickness of the different sections of the road with respect to the GFC drawings.

•              The bitumen prime coat and tack coat application should not exceed the prescribed limits.

 This is because, when the road gets heated up under the sun, the excess primer tends to melt and ooze out of the top of the road. This phenomenon is called as bleeding.

•              Check if proper slope has been given for the drains so that water does not stagnate. 

• Check the functioning of all electrical  and communication services provided along the road and the location of the signboards and reflectors.

TOOLS AND EQUIPMENTS

LABORATORY TESTS