Effect of lime as a modifying additive on the physical and mechanical properties of special concrete

Introduction . The paper considers possibilities for improving the physical and mechanical properties of special concretes, including heat-resistant concrete, gypsum concrete for manufacturing wall panels for industrial and civil buildings, by modifying them with lime. Aim . To examine the structural modification of heat-resistant concrete and gypsum concrete for improving their physical and mechanical properties and increasing their durability. Materials and methods. A finely ground additive, IM-2201 spent catalyst, was added to the heat-resistant concrete mixes. Slaked lime was used as a process activator at a concentration of 10 %, causing an increase in the compressive strength of the tested materials compared to products of the same composition with no lime added. An additive in the form of 5 and 10 % quicklime was introduced to increase the strength of gypsum concrete made from high-strength gypsum. The electrode potentials of steel in high-strength gypsum were measured. Results . Compressive strength tests on samples of heat-resistant concrete made from Portland cement with 10 % added slaked lime revealed a strength of 32 kgf/cm 2 . Electrochemical studies of steel corrosion in gypsum concrete indicated that adding 10 % quicklime to gypsum concrete not only increases the strength of products but also contributes to anti-corrosion processes. Conclusions . Heat-resistant Portland cement concretes added with IM-2201 spent catalyst and 10 % slaked lime, impregnated with 30 % orthophosphoric acid, have physical and thermal properties satisfactory for concrete operation at 800 °C. Steel reinforcement in gypsum concrete is protected by adding ground quicklime to the gypsum concrete as 10 % of the weight of the gypsum, thus enabling its use in the production of gypsum concrete panels in industrial and civil buildings.