Fly Ash Concrete – Part One: The Bad, The Ugly…

As makers of luxury concrete fireplaces and fire pits, I believe that we have a responsibility to make our manufacturing process as sustainable and energy-efficient as possible. And in the world of green concrete, nothing gets my mixer turning faster than supplementary cementing materials (SCM). I know what you’re thinking: “wow, that sounds unbearably sexy!” Well, let me assure you that it is.

SCM refers to a group of materials with ‘cement-like’ properties that can be blended into concrete to reduce the amount of cement required to achieve a similar or better product. SCM’s are most often recycled industrial byproducts with names like fly ash, slag and silica fume. These are largely the waste products of coal-burning power plants.

Okay, so we used the word ‘recycled’ so that’s good, but the benefits of SCM’s actually go much further. In our case, in the manufacture of our fireplace surrounds, tiles and fire pits, we utilize fly ash, so that is what I will focus on here.

Whether you are a self-professed concrete nerd like myself or you have any interest in sustainability and green technology, I think it is hard not to be impressed by the resourcefulness and ingenuity that allowed us to take two widely used, but very energy intensive processes and make them play nice together: I’m talking about coal-fired power plants and concrete.

Coal-fired power plants speak for themselves: they’re inefficient, non-renewable, inelegant and unfortunately, a major source of the world’s electricity. According to the US Energy Information Administration, coal accounted for 27 percent of the world’s power in 2007. That’s a lot. And just because I seldom get to throw around numbers of this magnitude (except googols, of course), this was almost 50 quadrillion BTU’s. Here in Ontario, 50% of our electricity comes from coal.

In the other corner we have concrete, which is the second most consumed substance on earth – next to water. This is obvious to most urban-dwellers and it is also clear that the uses of concrete are wide, essential to our buildings and our transportation methods, and, for the most part, difficult to achieve using other materials. What is less obvious is that the production of cement, the key ingredient in concrete, is a highly energy intensive process. In the most “elementary school science class” level explanation: rocks get crushed into a powder which is then fired in a kiln at temperatures up to 2000 degrees Celsius, which not only transforms it chemically, but embodies it with energy that allows it to react and form concrete. This process alone, accounts for about 4% of global carbon emissions.

It’s about now when most people should be thinking “okay, so where’s the good news?”

In part 2 of Fly Ash Concrete and Fireplace Mantels, we will look at the good news.