Carbonate-bonded construction materials from alkaline residues

Accelerated carbonation is a rapidly developing technology that is attracting attention as it uses CO2 as a binder to make construction materials. Originally stemming from geochemical and environmental research into CO2 sequestration or waste remediation, accelerated carbonation has been developed into a technology that enables to transform alkaline precursors into products that meet technical requirements for use as aggregates or shaped blocks. Alkaline precursors can be manufactured from primary resources or derived from industrial residues: a.o. metallurgical slags, incineration ashes and concrete recycling residues are prone to carbonate under controlled conditions. Moist carbonation of shaped Ca-silicate rich precursors at elevated curing temperature and CO2 concentration or pressure has delivered the most promising results so far. This letter presents an overview of current accelerated carbonation approaches to make carbonate bonded construction materials from alkaline residues. The general carbonation mechanism is explained and two application routes are exemplified: i.e. production of lightweight aggregates and compact blocks by accelerated moist carbonation.