Cement is to our buildings as corn is to our food supply. Just as corn is an ingredient in countless food products, cement is a building block for much of what is around us: our roads, our buildings, and our bridges. And, as with corn, plenty of cement substitutes promise to make our environment cleaner. But swapping conventional cement for “greener” equivalents is proving to be a tough challenge.
While many companies tout a more sustainable product than the limestone-based cement that dates back to the ancient Macedonians, cement in its current form is here to stay. One reason is logistics – most of us live within 20 miles of a cement plant, which means any drastic change will involve an overhaul of infrastructure, not to mention the massive education that will be required to retrain everyone from truck haulers to civil engineers. As more buildings rise while others are remodelled, the key to sustainable development will be the smart use of this material.
Efficiency and design has a prominent role in developing smarter cement and concrete structures. Less promising are the expectations of cement alternatives that perform well in a laboratory, but not in the concrete jungles of Seoul, Sao Paulo, and Los Angeles. Efficient design can help reduce the cement industry’s global impact, which contributes about five percent of the globe’s total carbon emissions. And yet cement and concrete are materials that offer durability and thermal properties, and can reduce energy and water waste throughout the places in which we live and work.
The holy grail of sustainable cement is for the material to be carbon-neutral or even carbon-negative. Novacem is one company that promises a more viable alternative to conventional portland cement. The UK-based firm’s product has a base of magnesium oxide and magnesium silicates (ie talc). The cement only needs be heated to a lower temperature than conventional cement, which is why Novacem touts its product as a carbon-neutral or even carbon-negative process. Novacem stands behind its twenty years of research and has won a bevy of awards – but its product and those of other companies have yet to scale.
According to Peter Taylor of the National Concrete Pavement Technology Centre, smarter design and usage would be a more effective solution. Taylor and other engineering professionals with whom I spoke suggested that cement and concrete will never be truly sustainable.
The question to ask is: can we make cement better?
Fly ash is one material that could contribute to greener concrete. The byproduct of coal combustion could replace up to 30% of limestone-based portland cement. Taylor, however, points out that the conservative nature of engineers lends them to stick with construction practices that have been in place for decades. But even small reductions in portland cement can reduce concrete’s CO2 impact. One example is the reconstructed Interstate-35 bridge in Minneapolis, which used a base of only 15% portland cement. The 30-foot tall sculptures that grace both sides of the bridge also contain a cement with photocatalytic qualities that remove carbon monoxide and other pollutants from the atmosphere.
The concrete industry is listening and focusing on both sustainability and resilience, according to Kevin Mlutkowski, the American Concrete Institute’s sustainability director. Mlutkowski explained that enhanced durability will be the key for the concrete industry to meet increased building demands without compromising the environment.
What architects, designers, and consumers all must do is to start looking at cement and concrete as valuable resources. Recycling concrete into kitchen countertops, instead of slicing granite out of mountains and quarries, is just one small example. Encouraging architectural features that repurpose concrete, instead of energy-intensive processes that involve pulverising and firing it, are another idea. New approaches, and an emphasis on smart use, reuse, and design, can burnish concrete’s reputation as a sustainable, not polluting, material.
Leon Kaye is founder and editor of GreenGoPost.com