Evaluation of the activity of pozzolanic materials

Abstract

Abstract Compressive strength and solubilisation tests were carried out to evaluate the pozzolanic activity of some natural and artificial materials. Strength tests were performed on mortar made with cements composed of 61% Portland cement clinker, 35% pozzolanic material and 4% gypsum. 1 : 1, by weight, pozzolana‐lime mixtures were used for the determination of the amount of SiO 2 , Al 2 O 3 and Fe 2 O 3 rendered soluble in cold HCl ( d = 1.12) by reaction between Ca(OH) 2 and the pozzolanic materials under investigation. Both of the mortar specimens and the pozzolana‐lime pastes were cured for 90 days at 25±1°C. The linear relationship found to exist between compressive strength and solubilisation of SiO 2 and R 2 O 3 is represented by the equation: where S is the compressive strength in kg/cm 2 of mortar cubes made with pozzolanic cement containing 35% by weight pozzolana; and sol. SiO 2 + sol. R 2 O 3 represents the percentages by weight of SiO 2 , Al 2 O 3 and Fe 2 O 3 rendered soluble by reaction between Ca(OH) 2 and the pozzolana constituent of the cement, and corrected for the sol. SiO 2 and R 2 O 3 of the original pozzolana. Granulated slag and diatomaceous earth gave results not satisfying the above relation; reasons for this are discussed.