Chris Craiker, The Architect’s Angle: Enemies of the Earth? How concrete and steel could become more eco-friendly | Home and Garden

Sustainability 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 high-rises.

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 next 30 years, concrete and 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.

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Jonas notes, “This not only saves energy and reduces carbon emissions from shorter transportation distances, but also increases 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 eco-friendly: 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 smelting is not changed.

One new method from MIT researchers to produce stronger and cheaper steel is to use iron and chromium which are abundant and produces no emissions other than pure oxygen. 

This works on small-scale factories where conventional steel plants only function with producing millions of tons of steel at a time. This could lead to more local production and reduce transportation costs as well.

Is this science fiction? Chris Jonas noted that engineers will continue to specify concrete and steel because of their long-life cycle and superior strength to withstand destructive natural and manmade forces while remaining relatively inexpensive.

With today’s focus on energy reduction and reducing greenhouse gases, these materials are often viewed negatively. Consequently, engineers and manufacturers are responding by specifying new combinations of ingredients that are more sustainable and cleaner.

The long-term concrete production industry’s goal is to be carbon neutral by 2050. The American steel industry has reduced its greenhouse gas emissions by over 35% in the last 40 years and now 90% of all steel is recycled.

The world needs to start recycling its by-products and plastic castoffs if we’re going to survive. It’s one thing to reduce our future omissions but what about all the waste we’ve already created and thrown away? We need to think outside the ubiquitous box.

Take a look at the progress of townhomes (and commercial space) under construction in downtown Napa. Known as Register Square, the units start in the high $700,000 price range.

Chris d Craiker AIA/NCARB Loves the Eiffel Tower, built in 1889, and only expected to last 20 years

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