CAIJUN SHI. ROBERT L. DAY and AR1E HUIZER
The University of Calgary
This paper deals with the effect of some sodium-based activators (Na2SO4 NaOH, Na2C03 and Na2SiO3.5H20) on strength development of two types of blended cements made with natural pozzolans. The two blended systems consisted of (a) natural pozzolan and lime, and (b) natural pozzolan and Portland cement. The experimental results indicate that except for Na2S04. the addition of the activators dcrreases the strength of natural pozzolan-Portland cement blends and increases the strength of natural pozzolan-itme blends. The determination of calcium hydroxide in hardened pastes shows thai in both systems, the addition of these compounds accelerates the chemical reaction between natural pozzolan and calcium hydroxide. The addition of Na2SO4 leads to the formation of an “eltringitc-lype” phase in both types of blended cement. The use of Na2SiO3.5H20 (water-glass) results in the formation of agglomerated cement-gel particles, while NaOH and Na2C03 do not produce a noticeable effect on the products of pozzolanic reaction.