Pilot project measures potential of CO2 in recycled concrete
A scientific pilot project has proven that concrete can reabsorb and permanently store up to 10 percent of the CO2 produced during its manufacture. In addition, concrete enriched with CO2 is stronger. This means that the proportion of cement in recycled concrete can be reduced.
A pilot project led by the Swiss Federal Institute of Technology Zurich(ETH) in collaboration with experts from the Swiss Federal Laboratories for Materials Testing and Research (Empa), the ETH Domain’s Water Research Institute(Eawag), the Paul Scherrer Institute(PSI) and the companies Kästli Bau from Rubigen BE and neustark from Bern, as well as 18 other partners, has shown that concrete demolition granulate fumigated with CO2 can save around 15 per cent of the greenhouse gas produced during its manufacture.
A total of 10 percent of this is achieved by the novel building materials enriched with carbonated concrete granulates. Another 5 to 7 percent can be achieved because the concrete granulate enriched with CO2 makes the cement compounds in recycled concrete stronger than normal concrete. This is the result of complex measurements carried out by Andreas Leemann of Empa’s Concrete & Asphalt Department, among others: “A reactive phase, in other words, which is newly formed in the granulate and produces a higher strength in the recycled concrete. That surprised us,” he is quoted as saying in a media release.
Further potential was also shown by the CO2 treatment of the so-called recycling water from water, cement and sand, which is produced during the cleaning of concrete vehicles and mixing plants. One kilogram of it could bind the considerable amount of 120 grams of CO2 gas. Life cycle analyses have summed up that the carbonated material can reduce the greenhouse effect by about 13 per cent net compared to concrete with conventional cement and without recycled material. For concrete with recycled material, the effect is still 9 percent.
The project leaders will present the research results to the public at the so-called closing event. It will take place on 6 December at ETH’s Audi Max.