Pozzolanic reaction in the presence of chemical activators Part II. Reaction products and mechanism

This paper has dealt with the pozzolanic reaction products and mechanism in lime-pozzolan cement pastes in the presence of Na2SO4 and CaCl2. X-ray dif fraction (XRD) analysis indicated that the hydration products in control li me-natural pozzolan pastes were calcium silicate hydrate (C-S-H) and C(4)AH (13) The addition of Na2SO4 to lime-natural pozzolan paste accelerated the pozzolanic reaction and resulted in the formation of AFt, instead of C(4)AH (13), which endorsed the paste a higher strength compared with the control pastes. The introduction of 4% CaCl2.2H2O decreased the pH of lime-pozzolan pastes, but favoured the formation of the solid solution of C(3)A . Ca(OH) (2). 12H(2)O-C(3)A . CaCl2. 10H(2)O. As the curing temperature was raised f rom 23 degrees C to 65 degrees C, it accelerated the reaction rates in all these pastes. The hydration products in the control and the CaCl2 activated pastes did not change with temperature, but AFm appeared in the Na2SO4 act ivated pastes when temperature was above 50 degrees C. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.