Mercury porosimetry: An inappropriate method for the measurement of pore size distributions in cement-based materials

• Published in: Cement and Concrete Research Vol. 30; no. 10; pp. 1517 - 1525
• Main Author: Diamond, Sidney
• Format: Book Review Journal Article
• Language: English
• Published: New York, NY Elsevier Ltd 01.10.2000; Elsevier Science
• Subjects: Applied sciences; Backscattered electron imaging; Buildings. Public works; Cement concrete constituents; Cements; Exact sciences and technology; Image analysis; Materials; Measurements. Technique of testing; Mercury porosimetry; Microstructure; Pore size distribution; Properties and test methods; Properties of anhydrous and hydrated cement, test methods; Mercury porosimetry; Image analysis; Backscattered electron imaging; Microstructure; Pore size distribution; Scanning electron microscopy; Pore structure; Cement paste; Void fraction; Method study
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/S0008-8846(00)00370-7

The conditions that must be met for mercury intrusion porosimetry (MIP) measurements to provide valid estimates of the pore size distribution of porous solids are reviewed. Evidence is presented indicating that these conditions are not satisfied in cement-based systems. In cement systems, nearly all of the mercury intrusion is held up until pressure corresponding to the threshold diameter is reached; subsequently, large and small pores are filled indiscriminately. Air voids, in sizes up to several hundred micrometers, are present in most pastes in substantial volume, unless the pastes were mixed under vacuum; these air voids are also not intruded until the threshold pressure is reached, and are recorded as fine (ca. 0.1 μm) pores. It is concluded that MIP measurements are useful only to provide threshold diameters and intrudable pore space measurements, which can serve as comparative indices for the connectivity and capacity of the pore systems in hydrated cements. MIP measurements should be abandoned as measures of the actual pore sizes present.