Concrete is a widely used building material, but its production has a huge environmental cost. It is responsible for up to 8% of global CO2 emissions, and its production process releases a large amount of CO2 into the atmosphere. The main culprit is the cement used in concrete, which must be heated to very high temperatures for clinker to form. This process releases a large amount of CO2, and also requires a lot of energy.
Alternative materials such as clay mixes are gaining popularity as they have a lower environmental footprint. Recycled concrete can also be used as an aggregate in new concrete mixes, although this limits strength and is not allowed in many jurisdictions. Manufacturers are responding to these limitations by altering concrete production processes and recycling old concrete debris for use as aggregates in new concrete mixes to reduce emissions. The use of cement and natural lime plaster wall finishes and concrete countertops can also significantly reduce total VOC concentrations within a home.
Carbonation in the pores of concrete occurs only at a relative humidity (RH) of 40-90%, when the RH is more than 90%, carbon dioxide cannot enter the pores of concrete, and also when the RH is less than 40%, CO2 cannot be dissolved in water.