BUILDING SERVICES

UNIT IX

ROADS AND

PAVEMENTS

ROADS

A Road is a thoroughfare, route, or way on land between two places, which has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways) each with one or more lanes and also any associated sidewalks and road verges. Roads that are available for use by the public may be referred to as public roads or highways.

DIFFERENT TYPES OF

ROADS

WATER BOUND MACADAM

ROADS:• Macadam is a type of road construction pioneered by

Scottish engineer John Loudon McAdam around 1820. • The method includes single-sized aggregate layers of

small stones, with a coating of binder as a cementing agent, mixed in an open-structured roadway.

• McAdam's road building technology was applied to roads by other engineers. One of these engineers was Richard Edgeworth, who filled the gaps between the surface stones with a mixture of stone dust and water, providing a smoother surface for the increased traffic using the roads.

• This basic method of construction is sometimes known as water-bound macadam. Although this method required a great deal of manual labour, it resulted in a strong and free-draining pavement.

• Roads constructed in this manner were described as "macadamized.

TAR BITUMEN ROADS

• The term bituminous materials is generally taken to include all materials consisting of aggregate bound with either bitumen or tar. Materials of this kind are used almost exclusively in road construction.

• The generation of dust from McAdam’s roads lead to the use tar as a dressing to bind the surface

• Tar was most suitable for this purpose as it could be made into a fluid on heating and stiffened on cooling.

• Tar also protects the road from the effects of water.• Bitumen was found to be less temperature susceptible than tar thus more

harder and stiffer than tar• It was resistant to deformation at high temperatures and softer than tar at

low temperatures.

ASPHALT ROAD• Asphalt also known as is a sticky, black and

highly viscous liquid or semi-solid form of petroleum.• It may be found in natural deposits or may be a refined

product. • The primary use (70%) of asphalt/bitumen is in road

construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete.

• Asphalt concrete is a composite material commonly used to surface roads, parking lots, and airports. It consists of mineral aggregate bound together with asphalt, laid in layers, and compacted.

• Asphalts rely on their dense, stiff mortar for strength and stiffness.

• An asphalt concrete surface will generally be constructed for high-volume primary highways having an average annual daily traffic load greater than 1200 vehicles per day.

• Advantages of asphalt roadways include relatively low noise, relatively low cost compared with other paving methods, and perceived ease of repair.

• Disadvantages include less durability than other paving methods, less tensile strength than concrete, the tendency to become slick and soft in hot weather and a certain amount of hydrocarbon pollution to soil and groundwater or waterways.

CEMENT CONCRETE ROAD

• Concrete surfaces (specifically, Portland cement concrete) are created using a concrete mix of Portland cement, coarse aggregate, sand and water .

• Concrete (cement) is produced from abundantly available limestone.

• Concrete roads have a long service life of forty years and during this service life concrete road do not require frequent repair or patching work .

• A vehicle, when run over a concrete road, consumes 15-20% less fuel than that on asphalt roads.

• This is because of the fact that a concrete road does not get deflected under the wheels of loaded trucks.

SOIL STABILIZATION

• Soil stabilization is a way of improving the weight bearing capabilities and performance of in-situ sub-soils, sands, and other waste materials in order to strengthen road surfaces.

• The prime objective of soil stabilization is to improve of in-situ soils by 4 to 6 times. • The other prime objective of soil stabilization is to improve on-site materials to create a

solid and strong sub-base and base courses. • In certain regions of the world, typically developing countries, soil stabilization is being used

to construct the entire road.• In the past, soil stabilization was done by utilizing the binding properties of clay soils,

cement-based products, and/or utilizing the "rammed earth" technique and lime.• As technology evolved, there have now emerged new types of soil stabilization techniques,

many of which are classified as "green technologies". • Traditionally and widely accepted types of soil stabilization techniques use products such as

bitumen emulsions which can be used as a binding agents for producing a road base. • However, bitumen is not environmentally friendly and becomes brittle when it dries out.• Portland cement has been used as an alternative to soil stabilization.

PAVEMENTSA Pavement in construction is an outdoor floor or superficial

surface covering. Paving materials include asphalt, concrete, stone such as flagstone, cobblestone, and setts, artificial stone, bricks, tiles, and sometimes wood.

In landscape architecture pavements are part of the hardscape and are used on sidewalks, road surfaces, patios, courtyards, etc.

DIFFERENT TYPES OF

PAVEMENTS

MURRAM PAVING

• Laterite, also called as murram, varies considerably in the proportion of stones (which are usually very small) to earth and sand.

• It ranges from a hard gravel to a softer earth embedded with small stones. They may be referred to as 'dirt roads' in common speech, but that term is used more for unimproved roads with no surface material added.

• Compared to sealed roads, which require large machinery to work and pour concrete or to lay and smooth a bitumen-based surface, Murram roads are easy and cheap to build.

• Murram which contains a significant proportion of clay becomes very slippery when wet, and in the rainy season, it may be difficult even for four-wheel drive vehicles to avoid slipping off very cambered roads into the drainage ditches at the side of the road.

• As it dries out, such laterite can become very hard, like sun-dried bricks

BRICK PAVING• Block paving also known as brick paving is a

commonly used decorative method of creating a hard standing.

• The main benefit over other materials to create a hard surface are that the individual bricks that go together to make up the block paved surface are able to be lifted up and then replaced.

• This allows for remedial work to be carried out under the surface of the paving without any visible notice to the surface once the paving bricks have been replaced.

• This kind of brick paving is said to be flexible paving.

• Typical areas of use would be for driveways, pavement, patios, town centre's, precincts and more commonly in road surfacing.

• There are two common makes of block paving brick, concrete and clay. Although other composite materials do exist to make up an individual brick. There are many different laying patterns that can be achieved using block paving.

• The most common of these is the herringbone pattern. This pattern is the strongest of the block paving bonds as it offers the most interlock, therefore making it a good choice for driveways and road surfacing.

STONE PAVING• Stone fulfills all the conditions of a good

pavement.• It is the most durable material for

pavement construction.• It is comfortable for travelling, clean, dirt

free, noise free and does not require frequent repairs.

• It is cheap• The nature of stone prevents its ever

becoming smooth or polished by use and hence it presents as good and firm a foot hold.

• Being uniform in its texture or hardness, it wears equally

• The closeness of the joints prevent little or no water penetration and it is never affected by frost and it never get into partial holes.

• Usually granites are used for the purpose of paving but stones which are hard and fine grained, containing very little mica, and which is very similar in texture, color and hardness are also used.

DRAINAGE OF

ROADS

INTRODUCTION

Water on or under the roadway is the single most significant cause of damage to the roadway. Problems related to water include rutting, cracking, potholes, erosion, washouts, heaving, flooding, and premature failure of the roadway.

To prevent these problems and help ensure a roadway achieves its designed service life, a drainage system is planned.

A good drainage system includes several elements, all of which must function properly and be well maintained:

• Surface drainage• Subsurface drainage• Culverts ,ditches and gutters.

SURFACE DRAINAGE

• Road surface drainage deals with the drainage of storm water runoff from the road surface and the surfaces adjacent to the road formation.

• Several elements can be used to intercept or capture this runoff and facilitate its safe discharge to an appropriate receiving location.

• After falling onto road surfaces, rainfall runoff drains to the lowest point and in moving across the road surface forms a layer of water of varying thickness.

• This water can be a hazard to the motorist. Splash and heavy spray are thrown up by moving vehicles reducing visibility, whilst the water on the pavement reduces friction between the tires and road surface.

• Design of the elements for this runoff must adequately cater for the safety and convenience of road users, including pedestrians and protect adjacent properties and the road pavement from damage.

Crown• A road’s crown should have

sufficient slope from the pavement centerline to the edge to make water effectively drain off the roadway surface.

• When the slope is too flat, water can pond on the surface and migrate through joints and cracks into the pavement or under the surface.

• This can lead to pavement cracking and potholes. Water that doesn’t drain off the roadway can also present a safety hazard to motorists

ShouldersTo aid in drainage, shoulders should be flush with the adjacent

roadway, slope slightly away from the roadway, and have no erosion problems or secondary ditches. Earth shoulders should be mowed every now and then.

SlopesSlopes are normally referred to by the ratio of the run to the rise The

degree of foreslope and backslope is determined by design standards and local conditions(e.g., cohesive soils, or rights of way). Local conditions may require that slopes be designed and constructed steeper or flatter than the design

SUB DRAINS

• A subsurface drainage system carries water from beneath the pavement to appropriate drainage features, like ditches or storm drains.

• The purpose of subsurface (or subsoil) drainage is to control the moisture content of the pavement and the surrounding material in order to maintain pavement strength and serviceability throughout the design life.

• The design and installation of subsurface or subsoil drains beneath / adjacent to road pavements is essential where groundwater or seepage is known or considered to be present.

• Subsurface or subsoil drains are provided in order to avoid the following types of premature failures:

• Loss of sub grade strength and shape due to an increase in moisture content in moisture susceptible materials;

• Overload of the sub grade due to hydrostatic transmission of live load through a saturated pavement; and/or

• Layer separation and pothole formation in the pavement. • Subsurface drainage systems are generally installed in a road either to remove water from the

sub grade and pavement materials or to intercept water before it reaches the road structure. • The elements of subsurface drainage include sub drains (under drains and edge drains).

Under Drains/Edge Drains• A well-maintained system of transverse and

longitudinal drainage pipes effectively intercepts and carries water out of the granular layer. Under drains carry water from the granular drainage layer to edge drains. Edge drains are installed under shoulders, longitudinally adjacent to the pavement.

• Edge drains are constructed during roadway construction where a perforated pipe is installed in a trench parallel to the roadway, which is then backfilled with an open-graded aggregate.

1. Caps of impervious soil are placed on top of edge drains to prevent surface water from draining into them.

2. Filters may be used to prevent fine-grained soil from clogging the open-graded aggregate or the pipe itself.

3. Water from the under drains is collected in a non-perforated edge drain pipe that discharges into a roadside ditch or a storm sewer system.

All sub drains should maintain the flow lines and the design slopes. The outlet water flow should be clear and uniform, indicating that erosion is not occurring and the system is not clogged.

CULVERTS• Culverts provide drainage

under driveways, roads, slopes, and adjacent areas.

• Their grade and direction should conform as closely as possible to that of the water they are carrying.

• Culverts are well maintained when the flow line and the design slope from inlet to outlet still exist.

• No sections have settled, and all joints are tight and not separated.

• The curtain walls are not exposed, and the downstream channel has not started to erode.

DITCHES• Ditches collect runoff from

the road surface. A well-maintained, smooth-flowing ditch will be free of heavy vegetation (tall grass, trees, cattails, etc.) and standing water, with enough grade to ensure self-cleaning and continuous flow.

• Ditches with flat percent-of-grade allow residue or debris to settle and fill in the ditch. If sediment accumulates, water may erode a new path outside of the ditch area.

GUTTERS• A gutter is a depression running

parallel to a road designed to collect rainwater flowing along the street and divert it into a storm drain.

• A gutter alleviates water buildup on a street, allowing pedestrians to pass without walking through puddles and reducing the risk of hydroplaning by road vehicles.

• When a curbstone is present, a gutter may be formed by the convergence of the road surface and the vertical face of the sidewalk; otherwise, a dedicated gutter surface made of concrete may be present.

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