Road Construction in the UK
Roads in the UK have been around for a long time. Tracks that go back into pre-history can still be seen, as can lengths of the superbly built Roman roads, from nearly 2,000 years ago. Road construction has moved on however…
The well constructed roads of both Telford and McAdam in the 18th century are the basis of many of today’s roads, yet it is an almost unbelievable concept that only two generations ago, in the late 19th century, what road were being built for.
Motorways aside, almost all of the established routes today were built, even as the country turned into the 20th century, not for the motor vehicle, but for horses and horse drawn vehicles.
Looking at the UK today, with some 35million cars on the roads, that is an odd concept to comprehend, but it needs a look at modern road construction to see how this is sustained.
After the Second World War, central government took charge of main road building, to carry on and expand the construction of by-passes, dual- carriage ways, and begin the programmes of motorway construction.
The ingredients that go into today’s road construction have not altered much in fifty years, but the advances in engineering technology mean that large and powerful machinery now take the place of hundreds upon hundreds of navvies.
The initial phase of building a road is clearance of trees, vegetation, and topsoil down to the sub-grade or base level.
This is normally achieved with a bladed bulldozer which can scrape away and down to the bottom level, above the up-holding sub-grade.
The bottom layer is made up of an unbound mixture of fine and course crushed stone, with crushed sand to get to the required load-bearing capacity and absorb traffic loads so that the underlying sub-grade will not suffer deformity.
Compaction is an important part of road construction. The better the compaction, the higher the potential for longer road life will be.
During the process machines may work to add or reduce moisture levels. Normally the sub-grade strength will increase as the moisture levels are lowered and kept so, until the paving layers are started.
The paving layers can begin once the drainage and any service lines are in place. Asphalt is usually placed in layers of varying thicknesses depending on the mix, and the place in the structure.
The exact type of asphalt will vary depending on its specific requirements. The size of the aggregate, the type of binder. It is laid by a paver machine which lays the mix at the required width and thickness.
It is followed by the compacting machine, usually steel rollers that press down the asphalt to the desired level of compaction. Additional layers are added, with a glue of asphalt emulsion between each to improve the bond between layers thus helping the strength of the completed structure.