Environmentally safer concrete

According to an article in the New York Times, a new bridge on I-35 outside of Minneapolis is built using a concrete blend that is friendly to the environment.

The bridge was built to replace a bridge that collapsed in 2007. The engineers were focused on finding a more durable concrete to prevent a future collapse. Their solution was to use multiple blends of concrete that were specialized for each component of the bridge.

Most of the concrete blends used in the project were made without Portland cement, the traditional bonding material with a high carbon footprint. Instead, Kevin MacDonald of Cemstone Products Company developed a way to use industrial waste products--fly ash and blast furnace slag--as the bond material.

Using these recycled materials reduces the carbon footprint of the bridge because their carbon output was already accounted for when they were originally produced. Portland cement also releases about one ton of CO2 for each ton of concrete.

MacDonald is just one of many researchers working on reducing the carbon footprint of concrete.