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All About Asphalt a mixture of aggregates and filler

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What is asphalt?

Asphalt is a mixture of aggregates, binder and filler. Aggregates used in mixtures can be crushed rock, sand, gravel or slags. In order to bind the aggregates into a cohesive and easy to mix substance a binder is used. This is most commonly bitumen as its chemical properties make it effective at locking and holding the mixture together.

What is it used for?
Asphalt has many uses, which it is why it is such a common and widely used product. As a material, it is a highly versatile and long lasting product. Here are some of the ways it can be used:
• Infrastructure (roads, railway beds or airport runways, taxiways)
• Recreation (playgrounds, bicycle paths, running tracks, tennis courts)
• Agriculture (barn floors, greenhouse floors)
• Industrial (ports, landfill caps, worksite)
• Building construction (flooring).

Ways of laying the material

Hand Laid
Using the hand laid method completes the majority of small and awkward jobs. This method is usually chosen when the job does not require complicated means of laying the material and plant is not available. This method comprises the asphalt being brought to the job on the back of a wagon covered by insulated sheets or in an insulated vehicle (hot box) to keep it workable. Then it is generally dropped or shovelled into wheelbarrows and taken to the area required. The skilled contractor will then use his experience to rake it level and ready to compact.

Machine Laid
As a material, Asphalt can be laid in large areas such as highways and car parks using pavers. It is added to the paver via a wagon or other suitable plant into a heated hopper housed in the machine at a temperature around 180°C. It is then distributed onto the surface and spread evenly leaving a smooth surface ready to be rolled and compacted vigorously to ensure stability and durability of the surface. This results in a solid and smooth surface. This process can be used for both binder and wearing courses and is perfect for car park surfacing or resurfacing.

Fun Facts

1. Asphalt is the predominant material used for road construction and maintaining the road network in Europe.
2. 25% of the total world’s production takes place in Europe.
3. Europe has over 2,500 production sites and over 9,500 companies are involved in the production and/or laying.
4. Some people still talk about tarmac or tarring a road. Since the 1990’s tar is not used anymore in road building.
5. Tar is totally different from bitumen. They are both black, but tar comes from coal and bitumen comes from heavy crude oil.

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What is a HSG47 in the Health and Safety

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The HSG47

(Avoiding danger from underground services)
The HSG47 refers to Article 47 of the Health and Safety Guidance Act. It outlines the dangers, which can arise from working near underground services and gives advice on how to reduce the risk.

Where the HSG47 guidance applies:

• This guidance applies to situations where underground services may be found and where work involves penetrating the ground at or below surface level.
• For road resurfacing, where ground penetration is contained within the wearing and base courses, the services encountered are likely to be limited to traffic sensor cables. Care will still need to be taken, in particular, to avoid damage to surface boxes for valves, pressure points, test points etc.
• All other work will be covered by this guidance including work in footways and kerbing, regardless of depth, as underground services may be found near the surface.
The dangers of underground services

Damage to underground services can cause fatal or severe injury. The main dangers and their effects under HSG47 are:
Electricity cables (Fire risk, explosion, electrocution, unrepaired live wires)
Gas pipes (Fire risk, explosion, leakage)
Water/sewage pipes (Pollution of water, flooding, mixing with gas pipes)
Telecommunications (Disruption of services, expensive repairs)

How to avoid the dangers of underground services when conducting work

A safe system of work has four basic elements:

1. Planning the work;
2. Plans for the work;
3. Cable and pipe locating devices; and
4. Safe digging practices.

Planning
This is where the designs for the planned work is conducted, where work is planned in advance to avoid certain services and where any required permissions and permits can be identified and acquired. This is when The CDM (Construction Design Management) is conducted so that management of the dangers can be assessed and built into the construction plans.
Plans

This is where plans for the design process are produced. These plans show the exact details of the required project, showing the location of work and location of underground services and how measures will be taken to work on these services and the health and safety measures taken to prevent injury.

Cable and pipe locating devices
This process involves using detecting instruments to detect pipelines or cables to exact measurements to ensure the location of the pipeline/cable matches with the plans of the project to ensure construction/digging practices can be undertaken safely and accurately.

Safe digging
This is where the digging/construction process is carried out using safe and protective means of construction. This involves indicating and marking where pipelines/cables are located in the ground; avoiding damage to services, prohibit the use of power tools near services and the proper reburial of all exposed services after the project.

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A Kerb Kerbstones and haunching

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What is the point of a Kerb

You may think a kerb as part of surfacing a car park or road surface is boring, well think again! They are an essential component of the everyday tasks of surfacing. They come in all shapes and sizes with each one providing a different message to the everyday person.

What is the point of a kerb?

Well, the answer to this is simple.

Kerbs…

  • Mark the end of a pavement to a road – essential for pedestrian safety.
  • Provide a corridor for vehicles to be directed by.
  • Create an edge to work with.
  • Help channel water towards the drainage.

Types of common kerbs
They are many types, but the two most common are the radius and half battered kerbs. All types need to be a British Standard product.

(These are only a selection. For more information on kerbs please contact Blackoak Surfacing)

Ok, but how is a kerbstone installed?

Concrete is laid on the ground, underneath where the kerbstone will be installed. This concrete provides the kerbstone with a strong structure and foundation. This process is called bedding. Once the bed is installed it is then finished. It is important that each is aligned to the closest measurement to ensure a quality and ascetically pleasing finish. A small gap should be left from the baseline and kerbstone to allow for drainage. This is given the deserving name of the drainage line.

The next process is called haunching. Don’t let the fancy name fool you it’s quite simple! Bedding makes sure that the base is strong and won’t submerse underneath the ground, however, haunching provides structural support by holding the kerbstone in place so it can’t move out of alignment, ensuring a professional finish. The haunching is also placed on the bed of concrete ensuring a solid fix.

What are the measurements?
Measurements can vary, however, these are the ‘British Standard’ measurements for the half battered and radius kerbs.

Type of kerb Height

(from bedding)

Width Length
Half battered kerb 225mm 125mm 915mm
Radius kerb 225mm 125mm 780mm
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