Rate of pozzolanic reaction of metakaolin in high-performance cement pastes

This paper assesses the hydration progress in metakaolin (MK)-blended high- performance cement pastes with age from the measurements of compressive str ength, porosity, and pore size distribution, the degree of pozzolanic, reac tion, and the Ca(OH)(2)(CH) content of the MK-blended cement pastes at a wa ter-to-binder ratio (w/b) of 0.3. Comparisons are also made with pastes con taining silica fume (SF), fly ash (FA), and control Portland cement (PC). I t is found that at early ages, the rates of pozzolanic, reaction and CH con sumption in the MK-blended cement pastes are higher than in the SF- or FA-b lended cement pastes. The higher pozzolanic activity of MK results in a hig her rate of strength development and pore structure refinement for the ceme nt pastes at early ages. Although the rate of pozzolanic reaction of MK bec omes slower after 28 days of curing, the pozzolanic reaction in the blended cement pastes with a w/b of 0.3 still continues at the age of 90 days. At this age, about half of the MK still are unreacted. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.