Activation of natural pozzolans, fly ashes and blast furnace slag

One disadvantage of the use of lime-pozzolan cements (LPCs) is their slow strength development; however, continuous increase of strength at later ages due to pozzolanic reactivity indicates that it is potentially possible to increase early strength development. Three methods were investigated to accelerate the strength development of an LPC made with a natural pozzolan from Bolivia: (1) addition of chemical activators to the LPC pastes (chemical method), (2) elevated temperature curing of LPC pastes (thermal method) and (3) prolonged grinding of the natural pozzolan (mechanical method).;Extensive optimization tests indicated that Na;Elevated temperature curing and prolonged grinding of natural pozzolan accelerated both the pozzolanic reaction and early strength development. An inverse relationship between temperature and the ultimate strength of lime-pozzolan pastes exists. Chemical activators showed different temperature sensitivity: Na;The main hydration products of lime natural-pozzolan, lime-LFA and lime-slag pastes in the absence of activators were calcium silicate hydrate (C-S-H) and C...