A Crash Course On Road Construction Materials

Road construction materials are one of the most essential elements of a road. The material that is used to make the road determines its cost, durability, and many other factors.

There are many diverse types of road construction materials that can be used for roads: asphalt and concrete are the most popular options. However, the use of alternative materials for road construction is becoming more popular. Alternative road materials can be cheaper and more environmentally friendly. The use of these materials may also benefit the economy if they are domestically sourced.

In this article, we describe a few of the alternative materials being used today to maximize sustainability in road construction.

What alternative materials can be used in road construction?

There is a wide array of alternative materials that can be used in road construction. Each has different physical and chemical properties to traditional asphalt and concrete. They are found in different physical states and require different processing before they can be used. Here are a few alternative road materials that we can incorporate into road construction today:

Natural rock

Natural rocks and soils are used extensively in road construction. Crushed stone is abundant and inexpensive, and includes rock types such as limestone, sandstone, granite, slate, and volcanic cinder. However, should we also not consider using phosphate waste rocks?

Reused by-product aggregates

Industry produces a vast number of by-products from its manufacturing processes. Many of these by-products can be successfully used in road construction. These include:

Air-cooled blast furnace slag (BFS)

A by-product in the manufacture of iron, when BFS is allowed to slowly cool it forms a stone-like material. This can be crushed and used as aggregate.

Granulated blast furnace slag (GBS)

GBS is produced when BFS is rapidly quenched with copious amounts of water. This produces a sand-like product, used as fine aggregate.

Steel furnace slag

A by-product in the production of steel, and formed in the basic oxygen system of the process, steel furnace slag consists of several materials including calcium silicates, ferrite, iron, aluminum, calcium, and manganese oxides. When air-cooled, the resulting crystalline material can be crushed to be used as aggregate in road construction.


Furnace and incinerator ashes can also be harvested for use in road construction. Bottom ash is like fly ash (and can be used in asphalt), while incinerator ash (after ferrous and non-ferrous metals have been removed) can be combined with clay to produce an artificial aggregate.

Manufactured aggregates

We can also make aggregates purposefully from certain materials and by-products of mineral extraction. These include:

Foamed blast furnace slag (FBS)

A pumice-like product, which can be crushed and used as lightweight aggregate.

Fly ash aggregates

Produced from fly ash, these are lightweight concrete aggregates.

Expanded clays, slates, and shales

When some clays, slates, and shales are heated to a semi-plastic state they develop an internal cellular structure. The heavier of these can be used for elements of road construction, such as prestressed concrete elements.

Manufactured sand

We can manufacture sand from suitable materials by crushing, screening, and washing, and then sometimes, by separating, recombining, and blending.

Polystyrene Aggregate

Waste-expanded polystyrene can be combined with normal aggregates to produce lightweight concrete.

Recycled materials

The use of recycled materials in road construction is now widespread. Such materials include:

  • Plastics can be used as stabilizing agents in soils or as additives to aggregates when producing hot-mix asphalt.

  • Demolition waste materials from disused and abandoned roads and buildings, including plaster, brick, concrete, and stucco, can make exceptional base aggregate. Some materials may be used as concrete aggregate.

  • Scrap tires. The crumb rubber from scrap tires can be added to asphalt to improve strength, reduce rutting, and improve the anti-skid qualities of road surfaces.

  • Foundry sands, a by-product of ferrous and non-ferrous metal industries, can be used in road construction as backfill material to build embankments, and as subbases.

Why we should consider using alternative road construction materials

As alternative materials become more widely available, the reasons for their use are becoming clearer. The ecological and economic benefits outweigh the drawbacks of their use. With less need to exploit natural resources, alternative materials are better for the environment. They are often more easily produced, more robust, longer lasting, and require less maintenance ─ so they are usually more financially viable, too.

At ACB Consulting, we are committed to helping improve the communities in which we live, work, and play – including how they are conceived, designed and created. To leverage our experience in sustainable design and construction, contact ACB Consulting.

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