This article reviews proposed technical approaches for the manufacture and use of alternatives to Portland Cement Clinker as the main reactive binder component for ordinary concrete construction in non-specialty applications, while giving lower net global CO2 emissions in use. A critical analysis, taking into account a wide range of technical considerations, suggests that, with the exception of alkali-activated systems, (treated in a separate paper in this issue,) there are only four classes of alternative clinker system that deserve serious attention with respect to global reductions in concrete-related CO2 emissions:
(A) Reactive Belite-rich Portland cement (RBPC) clinkers
(B) Belite-Ye’elimite-Ferrite (BYF) clinkers
(C) Carbonatable Calcium Silicate clinkers (CCSC)
(D) Magnesium oxides derived from magnesium silicates (MOMS)
A and B are “hydraulic” clinkers, (i.e. clinkers which harden by reaction with water,) C is a “carbonatable” clinker, (i.e. one which hardens by reaction with CO2 gas) and D can fall into both categories.