A is for Aggregate

Therese Dunphy

January 1, 2010

A geologist’s primer on issues uncovered throughout his 40-year career.

by Bill Langer

ag-ri-geyt (noun) — Particles of rock or inorganic manufactured material which when brought together in a bound or unbound condition form part or whole of a building or civil engineering structure. (A Dictionary of Quarrying Terms, 2006)

A while ago, Pam and I were reading the Alphabet Book to our grandkids, 6-year-old Donovan and 5-year-old Delaney. Every time a new letter came up, I shouted out an aggregate term….like, ‘A is for aggregate!’ By the time we got to ‘Q is for quarry,’ the novelty had worn off. Pam politely suggested that I save it for an Aggregates Manager article. Cool idea!

To me, aggregate is more than just a word; it’s a passion. I have written about it in Aggregates Manager for a dozen years and have studied aggregate for most of my career. During 1971, when I started work on my first map of aggregate resources, the United States consumed about 1.8 billion tons of aggregate per year. Today, almost four decades later, the United States annually consumes about 3.1 billion tons; that’s about 10.4 tons per person. The European Union consumes about 11.5 tons per capita; and 5.2 tons of aggregate are used on behalf of each and every person in Australia. World-wide society gobbles up well over 18 billion tons of sand, gravel, and crushed stone per year.

All of this aggregate comes from somewhere, and one might assume aggregate mining requires huge amounts of land. Actually aggregate mining uses only a fraction of 1 percent of the land area of most countries. For example, about 0.005 percent of the land area in Germany (per capita use about 8.4 tons of aggregate) is dedicated to aggregate mining.

Ultimately, geology controls the location and quality of the aggregate resources. Some areas are blessed with high-quality aggregate, others are not. Even if aggregate is plentiful, it still has to be mineable. Forty years ago, people were just beginning to worry about the environment. Today, aggregate producers not only take measures to protect the environment, but also have to deal with conflicting land uses. A study in Queensland, Australia, showed that just by eliminating conservation areas and high-density zoning from consideration for aggregate development, potential high-quality aggregate resources may be reduced by as much as 75 percent.

Today, producers also need a ‘social license to mine’ from the local citizenry. Obtaining such a license commonly requires following best management practices during operation and implementing a sound reclamation program after mining has been completed.

Consequently, although you may have aggregate directly under foot, you may not be able to mine it. Indeed, in some parts of the world where aggregate resources are plentiful, meeting local needs requires importing crushed stone or sand and gravel from 10’s or 100’s of kilometers away.

Putting all this together creates a really interesting puzzle. So even though Pam, Donovan, and Delaney roll their eyes when they hear it, I will still say, ‘A is for aggregate.’

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