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1. Education and Culture Lifelong Learning Programme ERASMUS Assist.Prof.Dr. Lucija Hanžič LECTURE 2 Capillary absorption in concrete www.fg.uni-mb.si/lucija/presentations/2008sakarya-lecture2.ppt 14 – 18 April 2008 Host institution Sakarya University Technical Education Faculty Turkey Home institution University of Maribor Faculty of Civil Engineering Slovenia

2. Assis.Prof.Dr. Lucija Hanžič Capillary absorption in concrete Figure 2. Feldman-Sereda model of hardened cement paste. R.F. Feldman, P.J. Sereda, A model for hydrated Portland cement paste as deduced from sorption-length change and mechanical properties, materials and Structures 6 1968) pp.509-519. Transport mechanisms of fluids in porous materials Difussion Fick’s law Suction Darcy’s law Capillary absorption Lucas-Washburn equation 2/6 University of Maribor, Faculty of Civil Engineering Microstructure of concrete Hydrated cement matrix is sol-gel where hydration products form solid sheets which are separated by thin layers of gel water. Gel water is firmly bonded and cannot be removed by heating to 100 °C. Cement matrix • Hydrated cement • Gel water • Fine aggregate • Pores Coarse aggregate Figure 1. Microstructure of concrete. Layers of sol-gel form the three-dimensional structure which is criss-crossed by interconnected channels (pores) of various diameters. Due to porous nature of concrete percolation of water and other liquids through concrete is possible. Figure 3. Types of pores in materials.

3. Assis.Prof.Dr. Lucija Hanžič Capillary absorption in concrete (a) (b) (1) Gravity force (2) Capillary force (3) Capillary pressure force (4) Atmospheric pressure force Viscosity force (5) (6) 3/6 University of Maribor, Faculty of Civil Engineering Capillary absorption Interactions between atoms on the solid-liquid-gass interface result in surface tension (γ). Figure 4. Shape of a droplet on the solid surface and shape of the meniscus in a capillary tube when (a) cohesive forces (K) are larger than adhesive forces (A) hence contact angle (Θ) is larger then 90° and (b) when cohesive forces are smaller then adhesive forces and contact angle is smaller then 90°. In the case of narrow tubes forces arising from surface tension are of the same magnitude as gravitational forces acting on the liquid column. Forces acting on the liquid column in a capillary tube: Figure 5. Forces acting on the liquid column in a capillary tube.

4. Assis.Prof.Dr. Lucija Hanžič Capillary absorption in concrete (7) (8) (b) (a) (c) 4/6 University of Maribor, Faculty of Civil Engineering Experiment setup By employing some simplifications and generalization derivation of Eq. (6) yields Lucas-Washburn equation, which describes liquid movement in porous material due to capillary absorption. Hight of liquid front is determined as Measurements of capillary coefficient were carried out by neutron radiography. Several subsequent images were made in time interval from 1 to 260 h and different liquids namely water, fuel oil and ethylene glycol were used. where kis capillary coeficient (m s-1/2) defined as: where γis surface tension (N/m), ris capillary radius (m), Θ is contact angle (°), and η is dynamic viscosity of the liquid (Pa s). Figure 7. Experiment setup (a) schematic representation of specimen wetting, (b) specimens during wetting and (c) specimen positioned in thermal column of nuclear reactor. Figure 6. Graphical presentation of Lucas-Washburn equation.

5. Assis.Prof.Dr. Lucija Hanžič Capillary absorption in concrete (a) (b) (c) (d) 5/6 University of Maribor, Faculty of Civil Engineering Results Figure 8. Results of capillary absorption analyses obtained by neutron radiography on concrete specimens for different liquids (a) water, (b) fuel oil and for ethylene glycol at 100 °C in concrete specimens (c) without additives and (d) with air-entraining agent. Lucas-Washburn equation is valid only in the initial time interval after the contact with the liquid has been made. Duration of this interval depends on the properties of the porous material, properties of the liquid and on temperature of the system.

6. Assis.Prof.Dr. Lucija Hanžič Capillary absorption in concrete 6/6 University of Maribor, Faculty of Civil Engineering Further reading Claisse P.A., Elsayad H.I., Shaaban I.G., 1997. Absorption and sorptivity of cover concrete, J. Mater. Civ. Eng., Aug., 105-110. Hall, C., 1981. Water movement in porous building materials – IV. The initial surface absorption and the sorptivity, Build. Environ. 16 (3), 201-207. Hall C., Hoff W.D., Taylor S.C., Wilson M.A., Beom-Gi Yoon, Reinhardt H.-W., Sosoro M., Meredith P., Donald A.M., 1995. Water anomaly in capillary liquid absorption by cement-based materials, J. Mater. Sci. Lett. 14, 1178-1181. Hanžič L., Ilić R., 2003. Relationship between liquid sorptivity and capillarity in concrete, Cem. Concr. Res. 33 (9), 1385-1388. Hanžič L., Nemec T., Ilić R., 2005. Determination of the capillarity coefficients of distilled water and oil in concrete by neutron radiography, Proc. 7th World Conf. on Neutron Radiography, Italian National Agency for New Technologies, Energy and the Environment, Rome, pp. 643-650. Martys N.S., Ferraris C.F., 1997. Capillary transport in mortars and concrete, Cem. Concr. Res. 27 (5), 747-760. Schoelkopf J., Gane P.A.C., Ridgway C.J., Matthews G.P., 2002. Practical observation of deviation from Lucas-Washburn scaling in porous media, Colloids Surf. A: Physicochem. Eng. Asp. 206, 445-454. Taylor S.C., Hoff W.D., Wilson M.A., Green K.M., 1999. Anomalous water transport properties of Portland and blended cement-based materials, J. Mater. Sci. Lett. 18, 1925-1927.  Vuorinen J., 1985. Depth of water penetration into concrete and coefficient of permeability, Mag. Concr. Res. 37 (132), 145-153.