VALSiGS - Improved Sustainability for Concrete through Silica Green Stone Valorization

The main goal of the project was value realization of Silica Green Stone (SiGS) through development of a green binder that can partially replace cement in concrete and thereby lower the environmental footprint of concrete. The environmental footprint of the concrete is lowered due replacement of cement, which has a high amount of CO2 emitted in the production phase. The full potential of the project, if the project is successful and all SiGS available is valorized, is around 227 GWh/y energy saving and a reduction in the CO2 footprint of around 180 kt CO2/y. In addition, such a development will be economically beneficial both for Eramet Norway and the end-users. Today SiGS is air cooled, but it is known from steel industry that the product quality of the cement replacement is improved by rapid cooling. During the project, Eramet got financial support from ENOVA to build a pilot for granulation of SiGS, so that two qualities of SiGS could be produced. The solidified SiGS was ground to a particle size that is comparable to cement, and tests were performed at lab and large scale where SiGS replaced cement. Further, tests were done to evaluate separation of alloy from the ground SiGS. It was found that this is not economically feasible. Both lab and large scale tests showed that SiGS can replace a significant share of the cement in concrete and still achieve a satisfactory strength development, from early to 28 day strength measured against a reference using 100 % cement.

Prosjektet har bekreftet hypotesen om at SiGS kan verdirealiseres i form av en sementerstatning som delvis kan erstatte sement i tørr- og våtbetong. En studie av hvordan dette påvirker fotavtrykket til ferdig betong, bekrefter at dette vil gi en vesentlig forbedring sammenlignet med bruk av ordinær sement. For Eramet gir innovasjonen en mulighet for å øke verdien på SiGS vesentlig, samtidig som det gir sluttbruker en mulighet til å erstatte en kostbar innsatsfaktor. Videre gir dette en vesentlig forbedring av miljøfotavtrykket til sluttproduktet (betong). For samfunnet for øvrig gir innovasjonen en vesentlig energi- og CO2-besparelse, og bidrar slik i arbeidet med å nå målene for kutt i CO2-utslipp frem mot 2030 og 2050. I tillegg vil det totale forbruket av jomfruelig materiale blir redusert når sement, som er helt eller delvis basert på jomfruelig materiale, blir erstattet med SiGS, som er et biprodukt.

The main goal of the project is to valorize Silica Green Stone through development of an alternative binder that can offer partial replacement of cement. Silica Green Stone, a slag that is a by-product from SiMn production has similar properties to blast furnace slag that is currently used as an alternative binder in concrete. Ground granulated blast furnace slag (GGBFS) is used in high proportions in concrete, with as high as 80% substitution. In the project the effect of changing the solidification process, combined with fine grinding of the slag, on key concrete- and dry concrete properties will be investigated. Further, the influence of Silica Green Stone on the sustainability of the end product where cement has been partially replaced will be documented. Based on information from GGBFS, the anticipated savings are in the order of 0.9 tons CO2 and around 1000 kWh per ton cement replaced. Key variables of the Silica Green Stone that will be varied to document the effect on the end product will be a) crystallinity of the slag and b) particle size. The effect on the end product will be evaluated through measuring the following variables: compressive strength, ductility, ASR, chloride migration and sulphate resistance.