Research on Optimal Proportion and Performance of Cement-Clay Slurry

For the cement-clay slurry commonly used in dynamic water grouting, consider adding coal ash to optimize the performance of cement-clay slag composite slurry and discuss the reaction mechanism of the slurry through microchemical element analysis; the orthogonal test was used to study the influence of various factors on material setting time, solidification ratio, water segregation rate, and the optimized ratio of the slurry that was obtained by integrating the unconfined compressive strength of grouting concretion body and slurry configuration cost. The results showed that the water-solid ratio had the greatest influence on the comprehensive performance, followed by the amount of coal ash admixture. The best performance of the composite slurry was obtained with a water-solid ratio of 0.8:1 and a cement:coal ash:clay:quicklime:sodium sulfate:water mass ratio of 1:0.45:0.20:0.05:0.07:1.32. Finally, by comparing the mechanical properties of the optimized slurry and the grouting concretion body, it is proved that the optimized slurry has superior performance to meet the general grouting project requirement.

CHARACTERISTICS OF FLOCCULES OF CLAY-SALT SLUDGE FORMED BY POLYACRYLAMIDE AND ITS COPOLYMERS

The main characteristics of aggregates formed during the flocculation of clay-salt slurry using polyacrylamide-based polymers with various types of charge and molecular weights were studied using a laser analyzer of particle size Lasentec D600L of the FBRM system. The effect of the polymer type on the size of the floccules formed and their density was shown. It has been established that when using non-ionic polyacrylamide and its anionic copolymers floccules with a size of 500-600 mm are formed, and when flocculated with a cationic reagent, the floccules do not exceed 300 mm It was shown that an increase in the molecular weight of the cationic polymer does not contribute to an increase in the size of the aggregates of the clay slurry particles. It has been proven that with the use of non-ionic polyacrylamide and its anionic copolymers, the density of floccules significantly decreases with increasing their size, which is an important property of fractal aggregates. If the charge density of anionic polymers increases, the aggregates density decreases, due to electrostatic repulsion between the negatively charged polymer and the negatively charged surface of the sludge. Analysis of the kinetics of the clay sludge flocculation process showed that when using non-ionic and anionic polymers, fast flocculation occurs, and the number of primary particles in the aggregate does not exceed several units. When using a cationic polymer, the filling of the intraflouclear volume with primary particles occurs due to the displacement of the liquid phase, which contributes to the formation of dense and compact floccules. The results obtained can be used for the selection of flocculant in order to improve the process of thickening clay-salt sludge in the production of potash fertilizers.

Kaolinite-Magnesite Based Ceramics. Part I: Surface Charge and Rheological Properties Optimization of the Suspensions for the Processing of Cordierite-Mullite Tapes

The present study aimed at investigating the influence of the concentration of sodium silicate and sodium hexametaphosphate on the dispersion of an aqueous kaolinitic clay slurry regarding further use for the tape casting process. The zeta potential of the kaolinitic clay slurry matched the requirements for tape casting. The addition of magnesite in the kaolinitic slurries tended to increase the zeta potential towards the required limit values. Despite this, the further addition of surfactants allowed improving the zeta potential in agreement with the tape casting conditions. Accordingly, the rheological behavior, under continuous and oscillatory flow conditions, of various mixtures of magnesite and a kaolinitic clay was studied. Regarding the pH and the zeta potential measurements, the E–F attraction prevailed at low pH value, and F–F or E–E attraction was predominant at high pH value. All slurries exhibited a shear thinning behavior, which was well-correlated by the Herschel–Bulkley model. It appeared that the best stability for the kaolinitic clay slurries was obtained while using 0.4 mass% and 1.2 mass% of sodium hexametaphosphate and sodium silicate, respectively. An increase in the magnesite concentration above 6 mass% led to a complex behavior with low cohesion energy due to the occurrence of soluble complexes.

Kaolinite-Magnesite Based Ceramics. Part I: Surface Charge and Rheological Properties Optimization of the Suspensions for the Processing of Cordierite-mullite Tapes

The present study aimed at investigating the influence of the concentration of sodium silicate and sodium hexametaphosphate on the dispersion of an aqueous kaolinitic clay slurry regarding further use for the tape casting process. The zeta potential of the kaolinitic clay slurry matched the requirements for tape casting. The addition of magnesite in the kaolinitic slurries tended to increase the zeta potential towards the required limit values. Despite, the further addition of surfactants allowed improving the zeta potential in agreement with the tape casting conditions. Accordingly, the rheological behavior, under continuous and oscillatory flow conditions, of various mixtures of magnesite and a kaolinitic clay was studied. Regarding the pH and the zeta potential measurements, the E–F attraction prevailed at low pH value, and F–F or E–E attraction was predominant at high pH value. All slurries exhibited a shear thinning behavior, which was well-correlated by Herschel–Bulkley model. It appeared that the best stability for the kaolinitic clay slurries was obtained while using 0.4 mass% and 1.2 mass% of sodium hexametaphosphate and sodium silicate respectively. An increase in the magnesite concentration above 6 mass% led to a complex behavior with low cohesion energy due to the occurrence of soluble complexes.