Maintenance Operations of Roads
The main objective of roads maintenance is to keep the roads in the original conditions as much as possible. The maintenance operations can be broadly divided into following categories:
- Drainage and Roadside areas
- Paved roads
- Structures and traffic control devices
1. Drainage and Roadside Areas
The drainage system consists of side drains, turnout drains, cut-off drains, drainage pipes, man-holes, chutes, cascades, culverts, drifts and sub-soil drains. The purpose of the system is to collect and conduct rain and ground water rapidly away from the road. Water can cause widespread damage to the road by weakening the pavement or foundations, and by erosion. The drainage system is, therefore the most important component of a road, even in locations with only occasional rainfall.
Roadside areas include shoulders and side slopes, and all surface areas within the road margins maintained by the road authority. Although these areas are not normally used by traffic, their maintenance contributes to the safety of the road users and to the stability of the road.
Drainage maintenance: The object of drainage maintenance is to ensure that the drainage system elements remain free of obstructions and retain their intended cross-sections and grades. They must function properly so that surface and ground water can drain freely and quickly away from the road and under the road.
The maintenance of ditches and drains consists of the following activities:
- Clearing and cleaning
- Reshaping, regarding and deepening
- Erosion control by regarding or realigning drains, repairing linings, providing or repairing scour protection
- Providing new turnout drains
- Erosion control by (re)lining drains, constructing cascades or catch pits or constructing flow spreaders
The maintenance of culverts consists of:
- Clearing and cleaning
- Erosion repair
- Cracking repair
- Head wall and apron repair
- Repair of invert
- (re)construction of culvert at correct level and fall
- Construct outfall basin
Maintenance of man-holes and drainage pipes comprises:
- Clearing manholes and underground pipes
- Replacing manhole covers and gratings
- Clearing the manhole area
- Cleaning catch pit sumps
- Relaying drainage pipes
The maintenance of shoulders is meant for:
- Removing obstructions
- Reshaping shoulders
- Vegetation control
- Adding shoulder material
The maintenance of slopes involves:
- Vegetation control
- Periodic maintenance
- Erosion control
- Slip repair
2. Paved Roads
Surface Dressing: Surface dressing is normally a periodic maintenance activity that uses mechanised methods, and can be used for dealing with a large surface area where:
- The surface is extensively worn
- The surface has become permeable or cracked, allowing water to penetrate the base and cause deterioration
- There is inadequate surface texture so that skid resistance is reduced
Graded seal: One layer of bituminous binder followed by either:
- Two layers of chippings of different sizes, the second layer serving to fill the gaps between the larger first stones and completely covering the road surface
- One layer of graded aggregate or gravel with stone graded over a wide range
Sandwich seal: One layer of chippings, followed by a layer of bituminous binder, covered by a second layer of chippings
Surface dressing is generally applied over the complete width of the pavement and over lengths of road ranging from a few hundred metres to several kilometres. With good planning and organisation, this work can achieve high outputs. It should be applied only in dry weather. It will usually be necessary to carry out some patching work before proceeding with the operation, particularly where there is base damage, subsidence, pot-holes, etc. Surface dressing will not correct depressions, deformation of road pavement or severe cracking.
Resealing: In certain circumstances, surface dressing is not appropriate, and other resealing options should be used. These include:
- Fog spray
- Slurry seal
A fog spray is a very light film of binder that is sprayed onto a ‘dray’ or hungry road surface to bind together and hold in place stone particles that otherwise would be picked off by traffic. The binder normally used is a bitumen emulsion and, where ‘pick-up’ of the binder by tyres is likely to occur, the surface may be blinded with a light sprinkling of find sand or crushed dust.
The slurry seal process uses a fine, graded, aggregate that is mixed at ambient temperature with water, dope (an additive) and bitumen emulsion that has a relatively high bitumen content. Some cement is also usually added. The mixture is applied to the road surface as a free-flowing slurry in a layer of 5-10 mm thickness. The mixture penetrates and seals surface as a free-flowing slurry in a layer of 5-10 mm thickness. The mixture penetrates and seals surface voids and cracks very effectively; hence the process is particularly well suited to the maintenance of old bituminous surfaces. Note that the skid resistance of slurry seals may be low, so they are sometimes used as a second treatment on top of a single surface dressing. With this method the tops of the chippings will penetrates through the slurry and provide the skid resistance. The slurry holds the chippings very securely and provides a durable, impervious and non-skid surface. Slurry seals may not resist reflection cracking in asphalt concrete surfacing.
Overlays: Overlays are a periodic maintenance activity and are applied over a large area.
Thin Overlays: Fill small surface deformation that are uncomfortable and dangerous to traffic. They improve surface texture where this is inadequate and dangerous to traffic. They also seal permeable surfaces that allow water to penetrate the road base and cause deterioration
Thick Overlays: The overlays are more durable than surface dressings, so tend to be applied to more important roads with heavy traffic and high speeds. Thick overlays for strengthening purposes are normally more than about 50mm thick and require detailed investigation and design. When deformation is severe, the overlay work must be preceded by the levelling of depressions and ruts, and the repair of pot-holes. This work may also be accompanied by the restoration of shoulders and ditches. Overlays must be applied during dry weather.
3. Structures and Traffic Control Devices
Bridges: The object is to keep bridges in sound structural condition and safe for traffic. When a bridge spans a watercourse, the water must flow freely at all flood levels without damaging the bridge or the waterway. Activities to be undertaken include:
- Cleaning and clearing
- Minor structural repairs, including the repair of loose or missing connectors and fixings, replacement of damaged planks, painting, wood preservation, pointing masonry
- Minor safety repairs, including repairs of barriers and safety features
- Major repair, including random stone filling, and repairs to retaining walls.
Traffic Control Devices: Traffic control devices include:
- Signs, reflectors and guard posts
- Guard rails
- Pavement markings
The maintenance operations include:
- Cleaning
- Repainting
- Repairing on the site
- Repairing in the workshop
- Vegetation control
- Replacing guard rails
- Pavement marking
- Replacing signs
- Repairing or relocating kilometre stones