Fabrication of foam concrete by use of novel foam generator — vortex jet apparatus: study of foam concrete properties

A new method of foam concrete production by use of vortex jet apparatus (VJA) is studied. The foam produced by VJA exhibits high stability and narrow size distribution of the bubbles’ diameter and the latter correlates well with diameters of foam concrete pores. VJA is a compact device allowing to generate foam without compressor, inhausting the air from the ambience resulting from vacuum in the center of vortex flow. Owing to additional opportunities (compared e.g. with usual axial ejector) like ability to suck the air, longer residence time and higher kinetic energy transformed further into dispersion of the bubbles new device lets to control the parameters of the foam and the density of the foam concrete, thus allowing to create foam with smaller diameter of the bubbles and higher stability. A mechanism of large pores isolation during water absorption tests was proposed. Main properties of foam concrete produced in this study: real and apparent densities, open and total porosities, thermal conductivity and thermal capacity, water absorption, compressive and flexural strengths have been measured; their values fully meet the requirements of Russian and French standards. The main part of pores was attributed to the open porosity because of very close values of total and open porosities. Equations characterizing relative mass of water absorbed by the foam concrete and the fraction of open porosity filled with the water were found as functions of apparent density. It was found that foam concrete production with wide range of densities (from approx. 480 till 1640 kg/m3) is easily attainable by means of VJA. Hence, the VJA could be used as an effective tool for foam generation and foam concrete production.