Aggregates

Aggregates can be coarse or fine. This is determined by whether the material passes through a sieve of a specified aperture size or whether the sieve retains them. Stone that has been broken up, gravels, sand and slag come into the category of aggregates. The term aggregate can also be a general term describing any quarried or dug material that has been through a grading process.

Asphalt

Asphalt has become something of a generic description for all types of bituminous mixtures. This can include coated macadam and rolled asphalt. European Standards will refer to asphalt in many instances when British Standards refer to bituminous mixtures

Bitumen

Normally a black or brown viscous liquid or a solid material, bitumen has adhesive properties and is made up of crude oil-derived hydrocarbons found in natural asphalt. Straight run bitumen - obtained after the final stage of distillation of crude oil of a suitable type. Normal grades used - 50 pen (hard) to 300 pen (soft). Cut-back bitumen - bitumen whose viscosity has been reduced by the addition of a suitable volatile dilutant or flux. Normal grades used - 50, 100, 200 secs.

Capping

This is a road construction material used below sub-base level – examples are top rock (crushed) and ready dug sand and gravels. These come into the category of low cost materials – others are sometimes used.

Cement

A compound of burnt lime, clays and shale, ground to a powder, which when mixed with water hardens fast. It is used as a binding agent in concrete and in mortar.

Chippings

These are crushed angular stone pieces of a single size material usually between 3 and 28mm – but can go up to 40mm. Crushed rock can be blended in with chippings in differing proportions and they lend themselves to a wide variety of applications.

Coated macadam

This is a material made of graded aggregate, coated with bitumen. The interlocked aggregate particles are responsible for the compacted road surface’s strength. Because strength of macadam is derived from mechanical interlock, crushed rock is the normal choice of aggregate

Concrete aggregate

Aggregate used to produce concrete for various applications, pipes, blocks, panels and ready mix for example

Crushed rock

A mechanical crusher is used to break rock - part of the process of producing sized aggregate for asphalt production and comes in two main types of either hard or soft stone.

Cut-back bitumen

Cut-back bitumen - bitumen whose viscosity has been reduced by the addition of a suitable volatile dilutant or flux. Normal grades used - 50, 100, 200 secs.

Dimension stone

These are large blocks of quarried stone, cut, shaped or carved. Having aesthetic qualities, Dimension stone is mostly used for architectural features and the external cladding of prestige buildings.

Granular sub-base

This is a graded granular material that meets DoT Specification for Highway Works, Cl.803, Type 1 and Cl.804, Type 2. In limestone quarries where impact crushers are used, GSB can be manufactured as the product of one crusher with no treatment other than straightforward screening that removes any oversize pieces. In igneous rock quarries the product of more than one crusher is required to meet the specification, or the GSB is produced by blending single size chippings. Recycled materials can also meet this specification for use, such as Optimix (50% limestone and recycled concrete aggregate) and Opti-blend (100% recycled containing slag, asphalt and concrete).

Gravel

Is a non-coherent natural mineral aggregate from natural disintegration of rock. It consists mainly of rounded pebbles for sub-angular rock fragments. It normally occurs in sand and gravel deposits or detritus.

HAPAS accredited products

Products accredited with HAPAS certification means that the material, production and laying are all externally audited to give customers confidence in these schemes. To be accredited with a HAPAS certificate, a product scheme has to meet certain performance criteria over a two-year period

Hardstone

Important in the top surface of roads, Hardstone, such as granite, improves skid resistance and prevents rutting. This is a highly durable stone.

Hoggin

It is the clay in hoggin that holds the mixture together when compacted. Hoggin is frequently used on top of good quality sand and gravel, and it is often required to meet the Type 2 GSB specification with no further treatment. The clay constituent can be high for certain purposes. It is most often used in foundations and on minor roads.

Hot Rolled Asphalt

This is a less widely used material and is made from coarse aggregate and sand with bitumen. The strength partly comes from the interlocking aggregate particles, but mainly from the sand and very stiff bitumen around the aggregates.

Limestone

A versatile stone found in many areas of the UK and ideal for construction use and for asphalt production.

Marine aggregates

Sand and gravel won from the sea bed by dredging.

Mortar

A mix of sand, cement and water used to bind together blocks, bricks and building stone in construction work.

Overburden

The soil and materials overlying the rock or sand and gravel to be extracted. It can be top rock or poorer quality material – this might be soft shale or clay. It may be sold as fill or soils which may be stored and used in the final restoration of the quarry

Portland stone

This is a high quality dimension stone originating from the Isle of Portland in Dorset. It is a strong uniform stone (Jurassic oolite) without internal laminations.

Pre-cast concrete

Factory-moulded concrete structures that are transported to construction sites for use. Used for flooring, staircases, drainage pipes, water tanks and specialist kerbing.

Quality Assurance Schemes

These are external monitoring schemes that continually check and confirm that material is being produced as stated within the companies Quality Manual. The external governing body awarded ISO 9001:2000 accreditations to companies that comply with national quality standards. This gives customers satisfaction in products produced under these schemes.

Quarry

An open surface working, from which virgin rock is extracted.

Quarry fines

Crushed, broken hardstone that passes through the smallest screen or aperture (usually 5mm or 3.35mm).

Railway ballast

This 50mm single sized aggregate must conform to a grading requirement the most significant of which is the Wet Attrition Test. The current specification requires a maximum Wet Attrition Value of 6 for high speed tracks therefore excluding most limestone.

Ready-mixed concrete

Sand, aggregates, cement and water mixed at a specialist plant or in a truck mixer then delivered to construction sites.

Ready-mixed screed

A semi-dry mixture of stand, cement, water, and in some cases proprietary additives produced at a specialist plant, then delivered to construction sites.

Recycled aggregates

Re-processed concrete, road surfacing, rock or bricks which have been removed from first use and crushed, screened and blended ready to be used again.

Run-of-quarry material

Large stones that have been blasted down from the quarry face and left untreated. Often used in dams, breakwaters and sea defences.

Sand

The type of sand and its origin should be stated, e.g. river sand, dune sand, pit sand, etc. Sand is small mineral particles resulting from the natural disintegration of rock and it needs to be relatively free of silt and clay. In soil mechanics sand is a size (2mm-63um) and (4mm – 63um) for aggregate in concrete.

Screed

A layer of material laid in situ, directly onto a base, bonded or unbonded, or onto an intermediate layer or insulation layer, for one or more of the following purposes: to obtain a defined level; to carry the final flooring. (Also see Ready-mixed Screed).

Screened aggregate

Sand, crushed rock and gravel that has been separated into various sizes by screening. Sand and gravel are usually produced to meet the requirements of BS EN 12620 (Aggregates from Natural Sources for Concrete) either as graded aggregates (40-5, 20-5, 14-5mm) or single sized (20/40, 10/20, 6.3/14, 4/10, 2/6.3mm). 3 fine aggregate gradings (C, M & F). Crushed rock produced in sizes to meet the requirements of BS EN 13043 for use in bituminous materials e.g. road surfacing, usually 20/31.5, 10/20, 6.3/14, 4/10, 2.6/3, mm and 3mm to dust.

Secondary aggregates

These are the waste products of other industrial processes that can be used to substitute natural aggregates. Examples include crushed glass, china clay waste, incinerator bottom ash and slag.

Self-compacting concrete

A concrete mix designed for use in confined areas where conventional compacting equipment cannot be used. It main feature is that it can move easily through congested reinforcement steel and requires no vibration to achieve high strengths and durability.

Straight run bitumen

Straight run bitumen - obtained after the final stage of distillation of crude oil of a suitable type. Normal grades used - 50 pen (hard) to 300 pen (soft).

Surface course

To improve wear and skid resistance the top surface of a road has a wearing course. It is made of Hot Rolled asphalt or coated macadam and laid over the base course. It is made using high PSV stone to improve wear and skid resistance.

Tar

Now little used for the production of coated materials because of environmental toxins, tar is a viscous liquid, black in colour with adhesive properties. It is obtained by the destructive distillation of wood, coal and shale.

Thin surfacing

Used in road surfacing to reduce noise, and also spray and skidding in wet weather.

Type 1

A granular material conforming to DoT specification, used in the lower layers of road construction; it is a mix of particles sized from 40mm to dust. When compacted it forms a solid base for roads and buildings. Type 1, which has to consist of crushed rock, slag or concrete, is the superior material and is the only one permitted for major trunk roads and motorways. Other sizes and blends are sometimes required to meet local requirements. Crusher run material from other types of crusher will meet the Type 1 and 2 BSB specifications with no further treatment (see under GSB).

Waterproof concrete

A mix of concrete which contains special additives which enable it to be used under water. It is used for bridge pier reinforcements, dock areas and for flood protection systems.