Aspects of determining the aggregative stability of water suspensions of mineral powders for building composites

Introduction. When using water suspensions of finely dispersed mineral systems of natural and anthropogenic origins as active agents in the production of concrete composites, an important factor in their effective use is to ensure the aggregative and sedimentation stability of solid phase particles before adding the solid phase into the reaction mixture. Methods and materials. The paper provides an algorithm for quantifying stability criteria according to the DLVO theory provisions as exemplified by a suspension of fine polymineral sand powder from the Kholmogorskoye deposit in the Arkhangelsk region (average particle size is 195 nm). In order to successfully assess the aggregative stability of this colloidal system, it is necessary to conduct experiments for determining the analogue value of the Hamaker constant, which was 0.5 •10-20 J for the mineral sand studied, in addition to experiments for determining the zeta potential of particles. This paper presents the results of the analysis according to the criteria of the value of the interaction energy (U.n) and the sedimentation rate (Vse) of a polymineral sand dispersed system (water suspension) calculated taking into account the analogue value of the Hamaker constant, zeta potential and dimensional characteristics of its solid phase particles, physicochemical properties of the dispersion medium. Results and discussion. It is shown that the determining factor of the aggregative stability of the suspension is the electrostatic barrier for particle interaction. Theoretical calculation showed that the aggregative stability of the system may be affected by its particles reaching their zeta potential of approximately 10-4 mV (a nearly isoelectric state). It is proposed to use the kinetic parameter of sedimentation - its velocity - to assess the kinetic (sedimentation) stability of this suspension - resistance to gravity, i.e. the ability to resist the dispersed system stratification due to the difference in particle densities between the dispersed phase and dispersion medium. Conclusion. The sedimentation rate is Vsed~ 4 nm/sec for the object under study in water dispersion medium with the averaged dimensional characteristics of 195 nm. At such a rate of solid phase particle precipitation, a dispersed system based on finely crushed polymineral sand from the Kholmogorskoye deposit can be considered sedimentatively stable.