Enemies of the
EARTH? How concrete and steel could become more eco-friendly
S
ustainability and energy efficiency are today’s watchwords for architecture and structural materials. Concrete and steel are the overwhelming heavyweights in our industry with the greatest impact on construction and the Earth. We use them in our foundations; they strengthen our buildings and create highrises. Unfortunately, concrete and steel are among the most energy-consuming products on Earth, using up to 15% of America’s annual energy production. In the CHRIS next 30 years, concrete and CRAIKER steel could provide 70% of the world’s housing and commercial construction for the next 2 billion people. Simply stated, concrete requires ground limestone to be heated to make cement. Steel requires iron to be smelted at high heat as well as recycling existing steel products. While steel is touted as a highly recyclable product, it still takes a lot of energy to transform it. I discussed these two products with Chris Jonas, principal and partner with ZFA Structural Engineers. He believes that we all need to specify and source as much of our construction products as local as possible. Jonas notes, “This not only saves energy and reduces carbon emissions from shorter transportation distances, but also increases
14 | DISTINCTIVE PROPERTIES
CHRIS CRAIKER the likelihood they are manufactured in the U.S., which has some of the most stringent environmental rules and regulations in the world.” Let’s look at concrete. The mixture of cement, gravel, sand, water and multiple aggregates produces 10 billion tons of concrete every year. In most of the world, concrete is the most used construction product, from bridges to high-rise buildings to humble residential structures. The concrete industry has tried to “Green Wash” itself by suggesting it can become more environmentally friendly by: 1. using fly ash, a byproduct of coal combustion; 2. blast furnace slag, a byproduct of iron conversion to steel; 3. micro-silica, a by-product of silicon chip production. While these are “industry spins,” reducing overall energy consumption is our mutual goal. We can’t eliminate concrete, but we have to make all aspects of its use more efficient and eco-friendlier. The future will be using more recycled products such as glass, plastic waste, and composite materials that will make concrete stronger and lighter as well as flame-resistant. In addition, by using locally-sourced aggregates transportation costs could be lowered to make a big eco-friendly statement. One alternative concrete is being developed by a British manufacturer that absorbs CO2 rather than emits it. Novacem uses magnesium sulfate to absorb up
to three times as much CO2 as traditional concrete emits. Another is a Norwegian startup, Saferock, which is testing a more sustainable concrete using geopolymers as a binder that lightens the load. Geopolymer’s carbon footprint is said to be 70% less than traditional concrete. Here’s another strategy. India produces 120 million tons annually of rice husks that are converted to ash, known as RHA. By using RHA as a geopolymer to make concrete, the cement ratio can be reduced significantly while creating strong, lighter concrete for the sub-continent. But it’s more than making concrete ecofriendly: it’s also reducing the amount of water used and wasted in the mixing and placement of concrete. Using renewable wood forms with organic oils for pre-cast concrete products will be common. We may not be able to eliminate concrete, but we should be able to reduce its carbon footprint. When you or your contractor asks for concrete delivery, ask what products are used, and what they’re doing to reduce their carbon footprint. ECO-FRIENDLY STEEL? Can we make steel more eco-friendly? The production of steel generates almost 5% of this nation’s greenhouse gases, 7% worldwide. Steel and concrete together produce 15% of the world’s emissions. It is said that one ton of steel generates two tons of CO2. This could double emissions in the next 15 years if the old ways of
December 2021
