Tag Archives: Concrete

Making Cement More Green

Cement is a material that is all around us and one that we hardly notice. It is the main ingredient in concrete, which is in the bridges we cross, the sidewalks we step on and the buildings we work in. Cement is the second most consumed material on Earth, only behind water. More surprising than the amount we consume is the amount of CO2 that cement produces. This single industry can make up anywhere between 5% to 10% of global emissions.

The main substance in cement is limestone that is heated to 1400C and then ground down to create a lumpy, yet solid substance known as clinker. Clinker is them combined with gypsum to form cement. The amount of heat needed to produce cement makes its energy and emission consumption very high. The heating of limestone creates CO2 as does the burning of fossil fuels to heat the kiln. The most common cement used for construction is Portland cement, which is the cheapest and consequently has the most environmental concerns.

Researchers at the Ecole Polytechnique Federal de Lausanne (EFPL) in Switzerland believe they have found a more efficient way to create cement. Their cement is produced by materials that are widely used and available- calcined clay and ground limestone. By mixing in their cement, known as LC3, with Portland cement, they believe they can bring down global CO2 emissions by several percent. It is not enough to just cut emissions, the new cement must also be strong and durable enough to be used as current cement is.

The EFPL just received a round of funding to further their research and we here at Coburn-Myers are looking forward to what they come up with.

A New Type of Concrete May Last Over a Century

A team of engineers at the University of Wisconsin-Milwaukee have a developed a new type of concrete that can last over 120 years. Known as Superhydrophobic Engineered Cementitious Composite (SECC), this water-repellent concrete is comprised of superstrong fibers that will leave bridges and roads without cracks for many years. Using superhydrophobic additives, mixed with superfine powders, the team was able to create a minute spiky surface within the concrete that was nearly impenetrable to water. An addition of unwoven polyvinyl alcohol fibers allows the concrete to bend without becoming brittle and breaking. The water repellent nature of SECC prevents the absorption of water, which is what leads normal porous concrete to crack. This new concrete is also more pliable, which means that if cracks do form, they will not grow and ultimately cause failure.

According to a list by the Government Finance Officers Association, typical concrete roadways can last up to 30 years and concrete bridges may last as long as 40 years. SECC, however, should be able to last four times as long on roads and three times as long on bridges. While this new concrete would cost more than traditional concrete, the decrease in maintenance costs over the life of SECC would more than make the cost worthwhile.

To test their new concrete, the engineers laid a 4-by-15- foot slab of SECC in a university parking garage. They implanted sensors within the concrete so they can monitor the moisture, stress and load levels. This will allow them to analyze the concrete in the real-world and hopefully prove the findings that they saw in the lab.