Calcined Clay-To-Limestone Ratio on Durability Properties of Concrete with Low Clinker CEM II/B-M(Q/LL) Cements

The present work focuses on the effect of different calcined clay-to-limestone ratios for a clinker replacement level of 35% on durability properties of CEM II/B-M(Q-LL) cements. Two calcined clay-to-limestone ratios, 0.5 and 0.83 expressed as Q/(Q + L), were considered in this investigation. In addition, some specific manufactured batches of finely ground calcined smectite clay and limestone filler with relative high chloride contents were opportunely considered for testing. This was done to investigate the viability of using alternative fuels in clinker, limestone filler and calcined clay productions without compromising the durability of concrete. The durability properties evaluated in concrete specimens with comparable 28-day strength demonstrated that these low clinker cements show a high resistance to chloride penetration, which is independently of calcined clay-to-limestone ratio and chloride content of the cement within the investigated compositions. Moreover, the high reactivity of calcined smectite clay is enough to mitigate ASR even at the cement composition with the lowest Q/(Q + L) and the increased alkalis content derived from calcined clay does not affect the performance in concrete regarding ASR. Nonetheless, it was detected that the increase of the calcined clay at the expense of limestone content in these cement compositions leads to a decrease of the resistance to freeze/thaw.