A MERCURY POROSIMETRY STUDY OF THE POROSITY IN PORTLAND CEMENT

Abstract

THE PORE SIZE DISTRIBUTIONS OF TWO SERIES OF CEMENT PASTES PREPARED AT WATER-CEMENT RATIOS 0.4 & 0.6 WERE DETERMINED AS FUNCTIONS OF AGE, USING MERCURY POROSIMETRY. THE CONTACT ANGLE OF MERCURY ON THOROUGHLY DRIED PASTE WAS MEASURED AS 117 DEGREES; FOR P-DRIED PASTE IT WAS FOUND TO BE 130 DEGREES. IT WAS FOUND THAT MUCH OF THE PORE SPACE PRESENT AT ALL AGES OCCURRED IN PORES BETWEEN 0.1 AND 0.01UM; THAT IS, IN BETWEEN THE CONVENTIONAL CONCEPTS OF CAPILLARY AND GEL PORE DIAMETERS. IT WAS FURTHER OBSERVED THAT PORE VOLUME LEFT UNINTRUDED BY MERCURY AT 15,000 PSI WAS SIGNIFICANTLY LESS THAN THE 28 PERCENT BY VOLUME THAT SHOULD BE PRESENT IN MATURE PASTES ACCORDING TO CURRENTLY ACCEPTED IDEAS OF THE NATURE OF CEMENT GEL. ON THE BASIS OF THESE OBSERVATIONS AND DIRECT EXAMINATION OF FRACTURE SURFACES OF CEMENT PASTE, IT WAS CONCLUDED THAT MOST OF THE SPACE PRESENT IS NEITHER CONVENTIONAL CAPILLARY NOR CONVENTIONAL GEL SPACE BUT MERELY SPACE BETWEEN FINE INDIVIDUAL PARTICLES OF CEMENT HYDRATION PRODUCTS. /AUTHOR/