Cement paste microporosity analysis: a comparison of different experimental techniques

Dalia Bednarska,

Marcin Koniorczyk

Abstrakt

Microstructure defines almost all material physical properties of a substance. Thus, its proper identification is essential for the assessment of material durability. Porous materials constitute the vast majority of those applied in civil engineering. The most important parameters describing a porous structure are the specific surface area, the shape and volume of pores and the pore size distribution. There are several methods which provide such results; however, each of them has some drawbacks. The main purpose of this paper is to compare results obtained by means of various methods commonly applied to the investigation of microstructure. These methods are mercury intrusion porosimetry (MIP), low temperature sorption of nitrogen and thermoporometry (TPM). The experimental research is conducted on aluminium oxide, which is characterised by unimodal pore size distribution and hardened cement paste prepared using portland cement (CEM I 42.5R with water-cement ratio equal to 0.5. The results obtained by the above-mentioned methods are thoroughly described and compared in this paper. Each of the presented approaches has some limitations; therefore, in order to receive a reliable description of porous microstructure, one has to apply at least two different experimental methods.

Keywords: porous materials, porous structure, cement paste, mercury intrusion porosimetry, low temperature nitrogen adsorption, thermoporometry

Streszczenie
Wśród materiałów budowlanych przeważającą większość stanowią materiały porowate. Dokładna znajomość mikrostruktury jest kluczowa w ocenie ich wytrzymałości i trwałości. Istnieje wiele metod eksperymentalnych służących do analizy struktur porowatych. W niniejszym opracowaniu porównane zostały następujące techniki: porozymetria rtęciowa (MIP), niskotemperaturowa adsorpcja azotu oraz termoporometria (TPM). Badaniom eksperymentalnym poddano dwa materiały. Pierwszy z nich, tlenek glinu, jest materiałem referencyjnym o unimodalnym rozkładzie porów. Zgodnie z deklaracją producenta dominująca średnica porów wynosi 7.3 nm. Drugim zastosowanym materiałem jest zaczyn cementowy przygotowany na bazie cementu portlandzkiego CEM I 42,5R. Stwardniały zaczyn charakteryzuje się skomplikowanym rozkładem porów. Opisane techniki analizy mikrostruktury są komplementarne. Aby uzyskać wiarygodny opis struktury wewnętrznej materiałów o skomplikowanym rozkładzie porów należy zastosować co najmniej dwie metody badawcze.

Słowa kluczowe: materiały porowate, struktura porowata, zaczyn cementowy, porozymetria rtęciowa, niskotemperaturowa adsorpcja azotu, termoporometria, porous materials, porous structure, cement paste, mercury intrusion porosimetry, low temperature nitrogen adsorption, thermoporometry
References

[1] Neville A.M., Właściwości betonu, Pearson Education Limited, Kraków 2012.

[2] Giesche H., Mercury Porosimetry: A General (Practical) Overview, Particle & Particle Systems Characterization 23(1)/2006, 9–19.

[3] Léon y León C.A., New perspectives in mercury porosimetry, Advances in Colloid and Interface Science 76–77/1998, 341–372.

[4] Abell A.B., Willis K.L., Lange D.A., Mercury Intrusion Porosimetry and Image Analysis of Cement-Based Materials, Journal of Colloid and Interface Science 211(1)/1999, 39–44.

[5] Moro F., Böhni H., Ink-Bottle Effect in Mercury Intrusion Porosimetry of Cement-Based Materials, Journal of Colloid and Interface Science 246(1)/2002, 135–149.

[6] Sing K., The use of nitrogen adsorption for the characterisation of porous materials, Colloids and Surfaces A: Physicochemical and Engineering Aspects 187–188/2001, 3–9.

[7] Baroghel-Bouny V., Water vapour sorption experiments on hardened cementitious materials: Part I: Essential tool for analysis of hygral behaviour and its relation to pore structure, Cement and Concrete Research 37(3)/2007, 414–437.

[8] Garci Juenger M.C., Jennings H.M., The Use of nitrogen adsorption to assess the microstructure of cement paste, Cement and Concrete Research 31/2001, 883–892.

[9] Majda D., Ikonen T., Krupa A., Lehto V.-P., Makowski W., Application of thermoporometry for characterization of mesoporous silicon: In search for probe liquid aimed at large pores, Microporous and Mesoporous Materials 264/2018, 1–7.

[10] Brun M., Lallemand A., Quinson J.-F., Eyraud C., A new method for determination the simultaneous of the size and the shape of pores: the thermoporometry, Termochimica Acta 21(1)/1977, 59–98.

[11] Defay R., Prigogine I., Bellemans A., Everett D.H., Surface tension and adsorption, Wiley, New York 1966.

[12] Ishikiriyama K., Todoki M., Motomura K., Pore Size Distribution (PSD) Measurements of Silica Gels by Means of Differential Scanning Calorimetry: I. Optimization for Determination of PSD, Journal of Colloid and Interface Science 171(1)/1995, 92–102.

[13] Brunauer S., Emmett P.H., Teller E., Adsorption of Gases in Multimolecular Layers, Journal of the American Chemical Society 60/1938, 309–319.

[14] Barrett E.P., Joyner L.G., Halenda P., The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen Isotherms, Journal of the American Chemical Society 73(1)/1951, 373–380.

[15] Jähnert S., Vaca Chávez F., Schaumann G.E., Schreiber A., Schönhoff M., Findenegg G.H., Melting and freezing of water in cylindrical silica nanopores, Physical Chemistry Chemical Physics 39/2008.

[16] Ishikiriyama K., Todoki M., Evaluation of water in silica pores using differential scanning calorimetry, Thermochimica Acta 256(2)/1995, 213–226.

[17] Ishikiriyama K., Todoki M., Pore Size Distribution Measurements of Silica Gels by Means of Differential Scanning Calorimetry: II. Thermoporosimetry, Journal of Colloid and Interface Science 171(1)/1995, 103–111.

[18] Landry M.R., Thermoporometry by differential scanning calorimetry: experimental considerations and applications, Thermochimica Acta 433(1–2)/2005, 27–50.

[19] de Boer J.H., The Structure and Properties of Porous Materials, Butterworth, London 1958.

[20] Zhang M.Z., Ye G., van Breugel K., A numerical-statistical approach to determining the representative elementary volume (REV) of cement paste for measuring diffusivity, Materiales de Construcción 300(60)/2010, 7–20.

[21] Sarbak Z., Adsorpcja I Adsorbenty. Teoria i zastosowanie, UAM Academic Publishing, Poznań 2000.