Abstract: The pore size distribution and number of air voids is an important characteristic, which substantially affects the system of air pores that protect concrete from cyclic freezing and thawing. The standard factor of pore distribution L is based on the Powers model, in which considerable simplifications are assumed. A better solution is provided by the Philleo factor, which determines the percentage content of protected paste located at a distance S from the edge of the nearest air void. Developing the concept put forward by Philleo, the PPV (paste protected volume) index was proposed. It is the ratio of the volume of the paste protected by air pores, at the assumption that S=200 μm, to the total paste volume. The PPV accounts not only for sizes and number of air voids, but also of aggregate grains, which is often disregarded in analyses. It is an extremely difficult task to determine four phases for real concrete, therefore an approach was used, in which an idealised image of concrete grain structure is generated on the basis of a numerical model. The results obtained from image analysis were compared with bubble spacing L given in the standard, and with the parameters developed by Philleo and Attiogbe. The analyses conducted by the authors shows that accounting for aggregate grains in calculations substantially affects the assessment of the quality of the air pore structure.
B I B L I O G R A F I APOWERS T.C., Air requirement of frost resistant concrete, Proceedings, Highway Research Board, V. 29, 1949, pp. 184-202.
[2] PN-EN 480-11 Determination of the characteristics of air pores in hardened concrete (in Polish), 2008.
[3] ASTM C 457, Standard test method for microscopical determination of parameters of the air void system in hardened concrete, 1990.
[4] WAWRZEŃCZYK J., MOLENDOWSKA A., Use of microspheres as an alternative method of concrete air-entrainment (in Polish), Budownictwo-Technologie-Architektura, No. 4, 2011, pp. 51-55.
[5] SPRINGENSCHMIDT R., BREITENBÜCHER R., SETZER M.J., Air-entrained concrete – recent investigations on the fine sand composition. Waiting time before compaction and redosing of air-entraining agents, No.11, 1987, pp. 742-748.
[6] SOMMER H., Choosing admixtures for air-entrained concrete, Concrete werk-Fertigteil-Technik, No. 12, 1987, pp. 813-816.
[7] PHILLEO R.E., A Method for Analyzing Void Distribution In Air-Entrained Concrete, Cement, Concrete and Aggregates, No.2, 1983, pp. 128-130.
[8] ATTIOGBE E.K., Volume Fraction of Protected Paste and Mean Spacing of Air Voids, ACI Materials Journal, No.94-M66, 1997, pp. 588-591.
[9] SHANSHAN J.,JINXI Z., BAOSHAN H., Fractal analysis of effect of air void on freeze-thaw resistance of concrete, Construction and Building Materials, No. 47, 2013, pp. 126-130.
[10] ELSEN J., LENS N., VYNCKE J., AARRE T., QUENARD D., SMOLEJ V., Quality assurance and quality control of air entrained concrete, Cement and Concrete Research, V.24, No.7, 1994, pp. 1267-1276.
[11] ATTIOGBE E., Mean spacing of air voids in hardened concrete, ACI Materials Journal, No.90-M19, 1993, pp. 174-181.
[12] SNYDER K.A., A numerical test of air void spacing equations, Advanced Cement Based Materials, No.8, 1998, pp. 28-44.
[13] SADOUKI H., VAN MIER J. G. M., Meso-level analysis of moisture flow In cement composites using a lattice-type approach, Materials and Structures, No. 30, 1997, pp. 579-587.
[14] ZHENG J. J., Li C.Q., Three-dimensional aggregate density in concrete with wall effect, ACI Materials Journal, No.99-M58, 2002, pp. 568-575.
[15] MOHAMED A.R., HANSE W., Micromechanical modeling of concrete response ubder static loading - part1: Model development and validation, ACI Materials Journal, No.96-M25, 1999, pp. 196-203. 