IMI commonly uses Supplementary Cementitious Materials (SCMs), or Pozzolans, in place of Portland Cement in our concrete mixes. SCMs reduce carbon emissions and add strength to our concrete. The most common post-industrial waste products used are Fly Ash, Slag and Silica Fume (a.k.a. micro-silica.) All three of these materials would end up in landfills if not used in concrete. Beyond recycling these waste products, each one significantly reduces the amount of Portland Cement we use in our mixes. This means less mining of virgin materials and saves the energy used to produce it.

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What does IMI do with old concrete?

Fresh concrete that is returned to our plants on our mixer trucks is recycled into bin blocks or is washed out of the truck and used as recycled base materials. Nothing goes to waste. Over the past three years, we have recycled nearly 70,000 tons of returned concrete into bin blocks.

Used concrete is crushed by some of our aggregate plants and also used as recycled base. In the past three years, we have recycled 87,000 tons of old concrete.

In the past three years, we have recycled 540,000 tons of post-industrial waste in our building materials

Fly Ash is a byproduct of coal combustion when used for the generation of electricity. Fly ash improves the workability of concrete and is commonly used when pumping concrete. It reduces bleed water during the finishing process. It is used to control set times in extremely hot weather.
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Silica Fume is a waste material from the production of silicon and ferrosilicon alloys commonly used in microchips. Silica fume is used to make concrete more impervious, so chemicals that would normally penetrate the concrete and weaken reinforcement (such as chlorides) are kept at bay. It also adds compressive strength to concrete.
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Slag is a byproduct of steel production that forms when iron ore is melted to a liquid form. Slag cement improves both the compressive and flexural strength of concrete. It also improves the permeability of concrete and aids in the resistance of chlorides and other corrosive chemicals. Slag makes concrete easy to pump and finish.
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Green Keys to Environmental Stewardship

Take a look at our corporate sustainability report, including the breakdown of tons of recycled building materials processed by each business unit.

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