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Regulation of the Water Demand of Mortar Mixes for Cellular Concretes by Plasticizers and Mechano-chemical Activation
Summary
Researchers tested polycarboxylate and naphthalene-formaldehyde plasticizers combined with mechanical-chemical activation of cement-ash blends for cellular concrete, finding that polycarboxylate superplasticizers provided superior dispersing effects and that moderate activation duration combined with optimal plasticizer dosage yielded the greatest improvement in mixture workability without increasing water demand.
The study investigates the influence of plasticizing admixtures of different chemical nature and the mechanical-chemical activation of components on the water demand and rheological properties of the mortar mixture for non-autoclaved cellular concrete. It is established that increasing the dosage of the plasticizer reduces water demand and enhances the mixture’s mobility, ensuring stable gas formation and the development of a uniform pore structure, which is critically important for thermal-insulating materials. It has been demonstrated that polycarboxylate super plasticizers exhibit a more pronounced dispersing effect compared to naphthalene-formaldehyde admixtures, as they create combined steric and electrostatic barriers on the surface of cement particles, preventing their aggregation. The application of mechanical-chemical activation of the cement–ash system increases its fineness, activates particle surfaces, and accelerates early hydration processes, which leads to an increase in the spread diameter of the mixture without additional water demand, even at minimal admixture dosages. Optimal activation duration has been identified, at which the maximum rheological effect is achieved. Excessive activation time, in contrast, results in over-grinding, an increase in specific surface area, higher water demand, and potential deterioration of structural stability. Iso-surface analysis of the system "plasticizer dosage – activation duration – flow spread" confirmed the synergistic interaction of these parameters: the greatest increase in mobility occurs when a moderate amount of plasticizer is combined with a rational activation duration, ensuring an optimal balance between workability and mixture stability. The obtained results enable a more precise optimization of the mix design and technological regime for producing cellular concrete, improving mixture workability, structural uniformity, and the operational performance of the final material.