Opus caementitium
Recent scientific breakthroughs examining Roman concrete have been gathering media and industry attention. Because of its unusual durability, longevity and lessened environmental footprint, corporations and municipalities are starting to explore the use of Roman-style concrete in North America, replacing the volcanic ash with coal fly ash that has similar properties. Proponents say that concrete made with flyash can cost up to 60% less because it requires less cement, and that it has a smaller environmental footprint due to its lower cooking temperature and much longer lifespan. Usable examples of Roman concrete exposed to harsh marine environments have been found to be 2000 years old with little or no wear.