High-performance concretes for machine building with nano- and micro-scale raw materials

Introduction. The unique combination of rheotechnological properties and mechanical performance opens up prospects for the application of self-compacting and high-strength concretes in the manufacturing of base elements for machines and industrial equipment. The processes of adsorption of modern plasticizers on various mineral and polymeric modifiers of concrete mixtures were investigated. The compatibility of nanoand micro-scale mineral additives in composite cementitious binders was determined using calorimetry with an improved semi-adiabatic setup. Materials and methods. The cementitious binders used were CEM 52.5N Portland cement (Asia Cement LLC, Russia) and Nanodur (Germany, Dyckerhoff GmbH); hyperplasticizers included Melflux 1641F, 2651F, 5581F (Germany), PCE TR-6088 (China), Sika ViscoCrete 240 HE Plus and 226-P (Russia); superabsorbent polymer; nanoand micro-scale mineral additives included microsilica MK-85, metacaolin VMK-45, microcalcite MM-315, marshalite Silverbond 15 EW, and ground silica-containing rocks. Selective dissolution, differential thermal analysis, laser granulometry, and semi-adiabatic calorimetry were employed. Results and discussion. The quality of ultrafine mineral additives determines their ability to chemically bind portlandite through pozzolanic activity. Among the investigated additives, microsilica and gaize demonstrated the highest pozzolanic activity. Thermal activation was effective for components consisting of crystalline silica (marshalite, ground quartz sand), resulting in a 25% increase in performance. There was no selective adsorption of hyper plasticizer molecules by superabsorbent modifiers based on sodium polyacrylate compositions. Metakaolin and tremolite exhibited high adsorption to hyper plasticizers among the mineral additives. The rapid evaluation of the influence of formulation factors on the setting of cementitious composites was tested on an improved version of the semi-adiabatic calorimeter. Conclusions. The presence of micro-scale mineral additives based on microsilica in composite cementitious binders enables the development of high-performance concretes adapted for machine building. The study of pozzolanic activity, adsorption capacity, and cumulative heat release curves has indicated the feasibility of replacing microsilica with metacaolin and the potential for its partial blending with finely ground natural gaize. Analysis of the thermal effects accompanying the hydration processes of the "cement-additive-water" system with calorimeters allows us to provide more efficient research on the compatibility of additives in high-performance concrete compositions.