The carbon uptake by carbonation of concrete structures – some remarks by perspective of TA

An issue which recently raised remarkable attention in both industry and politics with regard to CO$_{2}$-emissions of the cement industry is the uptake of CO$_{2}$ into concrete structures from the atmosphere due to weathering. Lobbyists urge to implement this overlooked sink of CO$_{2}$ within the global CO$_{2}$-balances. In this paper we examine the question whether the currently proposed methodology and database are sufficient for implementation. The experimental database is assessed to be doubtful due to inadequate testing. No reliable correlation of carbonation and age of buildings exist. Simple models are insufficient to allow a transfer in real buildings. A compensation of today's emissions with carbon that is sequestered by the existing building stock is implausible. The after-service life is assessed to be of higher importance. But the practicability and the economy of new procedures for enhanced carbonation of crushed concrete are uncertain. On the existing basis, the drafting of guidelines for IPCC appears to be very problematic. There are indications that a substantial fraction of CO$_{2}$ once emitted would remain within the atmosphere for thousands of years. ... mehrEven if CO$_{2}$ is sequestered with a long-term delay, damages caused by extreme events cannot be retroactively reversed. The cement industry finds itself in a tricky situation. In the medium term, there is no serious alternative binder in sight and the realization conditions of CCS are unclear. For this reason, to the author's perspective, reinforced R&D in the field of radical innovations of low-CO$_{2}$-binders is strongly recommended.