Оптимізація складів високоміцного бетону на механоактивованому в'яжучому з добавкою мікрокремнезему

Abstract

Стаття присвячена питанням отримання високоміцних бетонів шляхом механоактивації рядового портландцементу з органо-мінеральною добавкою, а також оптимізації складів бетону з урахуванням ресурсозбереження. Проведений експеримент дозволив встановити вплив незалежних факторів (x1 – вміст мікрокремнезему в в'яжучому – 5 ± 5 %; x2 - витрата в'яжучого в бетоні – 450 ± 100 кг/м3; х3 – питома поверхня (Sпит) портландцементу – 400 ± 100 м2/кг ) на фізико-механічні властивості бетону (міцність при стиску, Кр). На базі отриманих математичних моделей, що відображають вплив незалежних факторів на фізико-механічні властивості високоміцного бетону проведена оптимізація складових високоміцних бетонів.

The paper examines the problems associated with production of high-performance concretes by using a general purpose blended Portland cement which is to be mechanoactivated and modified with an organomineral additive, and with optimization of concrete mixes taking into account cost-effective use of resources. The experiment conducted in accordance with a tri-factorial D-optimum design enabled to establish an influence of independent factors (x1 – content of microsilica in the binder - 5±5%; x2 – binder consumption in concrete - 450±100 kg/m3; x3 – specific area (Ssp) of Portland cement - 400±100 m2/kg) on physical and mechanical properties of concrete (compression strength, Ks). It was established that the use of the mechanoactivated general purpose blended Portland cement with an organomineral additive (microsilica+C-3) makes it possible to obtain high-performance concretes which compression strength on the 28th day reaches 120 MPa. Optimization of concrete mixes was achieved on the basis of obtained mathematical models that reflect the influence of independent factors on physical and mechanical properties of a high-performance concrete. Three alternatives to select the optimum composition of a high-performance concrete with the use of two-dimensional diagrams were considered. The alternatives differed in the binder consumption of 350, 450 and 550 kg/m3. At the appropriate fixed levels of x2 factor, the diagrams were constructed as squares, which reflect the influence of the microsilica amount (x1) and specific area of the binder (x3) on the compression strength level of concretes added with a mechanoactivated binder on the 28th day, as well as on the softening coefficient. As a common limitation criterion for all three alternatives, the concrete softening coefficient not less than 0.85 (Ks ≥ 0.85) was found. The compression strength of concrete – 80, 90 and 100 MPa was assumed as the second limitation criterion. Solution of the optimization problem enabled to select the optimum compositions of high-performance concretes that can be used depending on the needed strength- levels for a particular task and taking into account the economic efficiency and current prices of energy, equipment and raw materials.