It’s no secret that here at Logix, we think concrete is a wonderful product. We love the malleability of it, the abuse resistance to both the wrath of man and nature, and its durability – that sense of permanence. With concrete, you can build amazing structures that last for hundreds of years. Of course, it’s also a product that can be easily misused – as evidenced by the many projects that turn into instant slums. The problem is that concrete can be vulnerable to installation difficulties. What better way to elevate the general opinion of concrete as a highly valued product than to improve its value as a green building material?
There are many levels of green. Deep green solutions in the concrete industry address the production of CO2 on two fronts. The first is the CO2 associated with the energy use in manufacturing, which can be and is being dealt with just like any other industrial operation. The concrete operation, which is an energy intensive industry due to the high heat required in the process, has reduced energy consumption by 37% since the first calculations in 1972. Another goal for a 10% reduction in CO2 has been set for 2020. Today, the cement industry fuel CO2 accounts for 3% of the US industrial emissions, compared to 9% for the few remaining iron and steel mills in the US.
Another way to reduce the carbon footprint is by displacing the Portland cement, which is only around 11% of the total volume of concrete. There is good engineering knowledge of the use of industrial by-products like fly ash, slag, and also foundry sand, mill scale and synthetic gypsum. There are also a few new sources of ash – for example from rice husks. This is a by-product that has had limited opportunities for re-use, and as such, is a bit of a ‘garbage’ problem. But rice husk can reduce to an ash that has many of the same properties as fly-ash – improved flow with lower water content for higher strength.
One perspective often overlooked is the opportunity to ‘value engineer’ the concrete work. More is not better if it’s unnecessary or adds no additional benefit. For example, 6” of concrete provides sufficient sound resistance for most uses, and 2” is sufficient to resist most air-born missiles, such as in a hurricane. Insulated concrete forms not only often pay for themselves through the right-sizing of the structure, but the savings they provide can also translate to a lower carbon count. ICFs can also easily form up a post and beam structural system, seamlessly marrying the benefits of both those worlds.
Ultimately, one of the key contributors to sustainability is to build something well for a long service life. With that in mind, we can think of few products that can actually ‘out-green’ concrete.