The extensive resource extraction and the enormous global CO2-emissions of the construction industry are becoming increasingly a challenge with regard to the aim of a sustainable future. Recycling of construction and demolition waste (CDW) can contribute significantly to the conservation of resources. The existing building stock therefore has to be considered as a raw material depot for future construction activities. Forced carbonation of recycled concrete aggregates (RCA) is a novel methodology and if additionally carried out in the course of processing, the aspect of climate protection can also be considered. Regarding forced carbonation, first industry implementations have already taken place and an increased future application is emerging. One difficulty is the uncertainty of the existing CO2-uptake potential of the RCA. Main influencing factors for the achievable storage potential are the grain size and the duration of the CO2 exposure time as well as the appropriate ambient conditions like humidity of the grains and CO2 concentration. An exact determination is essentially possible after the carbonation has taken place by measuring masses before and after carbonation monitoring the experimental conditions. The present study shows a simply applicable and efficient method for determining the CO2-uptake potential on material samples which can be taken from the still existing construction stock before demolition. Available data show the possibility of determination also for RCA from different sources, showing an influence of concrete quality and natural exposure time after processing the demolition concrete waste.