Monday 13 June 2016

Cross Section of Road



Typical Road Structure Cross Section 





1. Soil Subgrade:


 It is the natural ground on which the road is built which serves as a working plate form for the construction of upper pavement layers generally natural gravel. however in circumstance where the material is not suitable eg. clay, sand etc suitable material should be excavated from elsewhere to replace.

2. Sub Base Course:


This is laid on the subgradeIt is usually not provided on subgrade of good quality. This layer is also generally gravel material. It should be clean and free from organic matter and should be able to be compacted by roller, to form stable sub-base.

3. Base Course:


It is the layer immediately under the wearing surface, base course lies close under the pavement surface subjected to severe loading. The material used must be of extremely of high quality and its construction must be done carefully.

4. Surface Course/Wearing Course:


The top layers of pavement which is in direct contact with the wheel of the vehicle. Usually constructed of material in which bitumen is used as binder materials.




Construction of Wearing Course Road







Monday 22 February 2016

Stages in Road Construction





Stages in Road Construction


The basic construction process for building a road is similar for any road. The differences arise in the finishing of the road or the surface materials used to finish a road. The process begins with road design, including surveying the route, allowing for drainage and considering the expected volume of traffic and planned development in the area. Next, the important base layers are completed using graders, bulldozers, compactors and levelers, and then the surface layer is applied.


Clearing and Excavation

The area on which the road is going to be built on must be cleared of all vegetation. This includes removing any unwanted material i.e. Tree roots, grass, loose soil, preparing the leveled surface. Excavation is done when the existing material is not suitable for the road, other suitable material is dumped in the excavated portion.




Sub-Grade Preparation


The road takes shape as diggers, excavation plant machinery and bulldozers mount gravel material over the area where the future pathway will run. The road surface is then formed with a camber, and leveled by graders. Culverts and drains, consisting of large concrete pipes, are laid to prevent the road from flooding by draining away groundwater, sewage or stormwater. Sub-grade act as a cushion for other layers i.e.  In order to achieve durable road sub-grade should be strong.





Sub- base and Base materials

The sub-base and base should be laid as soon as possible after final stripping to formation level, to prevent damage from rain or sun baking which could cause surface cracks. The most commonly used material for use in sub-bases is termed Type 1. This is an unbound material made from crushed rock, crushed slag, crushed concrete, recycled aggregates or well burnt non-plastic shale. It contains particles of various sizes, the percentage of each size being within a defined range. Up to 10% may be natural sand. The predefined and calculated range of material sizes contained means that once compacted, it will resist further movement within its structure. In other words, it tends not to sink with time (though it will sink if not compacted properly when laid).
All materials on arrival from the borrow pit must be protected from the weather, as drying or wetting changes the composition. They must be spread evenly. They are laid in layers of 100mm - 200mm compacted thickness, the thickness of the layers being gauged by various means including pegs and lines, sight rails and a guide wire.


                        Uncompacted type 1

                    After compaction



Surfacing

Both the surface course and binder course are included in the part of the road structure termed the surfacing. Normally, it is layed as two course binder and surface.
The binder course helps distribute the load of traffic above onto the base course, which is usually a weaker material. It also provides a flat surface onto which the normally thinner surface course is laid. In new construction, typical thickness is between 45mm and 105mm. Thickness may vary considerably where a new binder course is laid to an existing road structure for strengthening purposes. Stone sizes used are 10, 20 or 14mm. The thicker the binder course, the larger the stone size. Materials used include open graded macadam, dense coated macadam and rolled asphalt. 

Before the last layer of asphalt or chip seal is poured, the sidewalks and drains have to be be finished. The Construction work is concluded by placing the appropriate road signs at the places specified by engineers and the application of road markings.



  
Asphalt 
 

Chip Seal

Saturday 16 January 2016

Road construction: History



Road Construction: History

The use of Road infrastructure has been part of us since Adam, even though now there are better and sophisticated ways of road construction now.  Road Transport is the number one mode of transporting people, goods and services in most parts of the world. This makes people wonder how road construction all began.
The first road was built by ancient Romans an extensive and durable system of roads to serve their needs. The Roman road-building era began in 312 BC. The roads provided economic and military access from Rome to distant parts of its far-flung empire. The first road constructed was the Appian Way, which led from Rome to Brundisium (now Brindisi), a port in what is now southern Italy. The Appian Way was the main route to Greece, and it ran over 560 km.
workers building road with cobblestones

The roads were constructed by carefully placing cobblestones in the ground, these cobblestones are cut in specific patterns before they are placed.

               Finished road built with cobblestones


The construction techniques were simple but effective as they served the means of transporting goods and services form one place to another by land. The Appian Way in Rome still exists although it was constructed 2300 years ago. The Roman roads are considered the beginning of road construction, Telford Pavements are known as the second step of this process, followed by the Macadam Pavements that ultimately lead to the Bitumen Roads, now concrete roads have added another dimension to stability and strength of the roadways.
Today, road construction involves traffic studies, road alignments, road design, and drainage systems, slope gradients, use heavy construction equipment for rapid, effective, durable and easier to build roads.
Research is still been made by civil engineers on newer ways of designing and building the most efficient and cost-effective roads.

References
  • History of Roads, auuuu.com
  • Road construction :History and procedure, brighthubengineering.com
              

Wednesday 13 January 2016

ROAD WORKS AHEAD

This Blog as an Engineering Solutions Site has been created to provide smart engineering solutions particularly regarding the construction of Roads. We live in a country where huge sums of money is spent on road construction, however, these same roads have to be patched soon enough due to the development of pot holes.




My passion for creating and fixing things as an Engineer with the Feeder Roads Department has further increased the need to start this blog as a central location where smart standards are set and proper engineering rules and procedures followed to ensure value for money.


Feeder roads linking small towns and villages need to be developed and properly as they link major food production sites in Ghana to the Cities.




My name is Robert Arthur, I'm a Civil Engineer with experience in Road Construction.