Blended systems are a promising solution for the sustainable cements of tomorrow.However the microstructural development in such systems is still poorly understood and limits the prediction of their properties.The main issue is to isolate the impact of the reaction of the SCM microstructural evolution in blended systems.Using ternary systems consisting of cement blended with quartz and slag or fly ash we isolated the effect of the SCM.Our results shows that at high replacement slag and fly ash reactions becomes limited at later age whereas in systems with low replacement level (10%) the reaction continues further.Combining microstructure analysis and MIP we show that the space is the limiting factor for the reaction of slag and fly ash at later term.When the pore entry size of the pore structure reaches about 6 nm the kinetics of the reaction was slowed-down and the radius does not reduce further in size.