The strength and deformability of cement stone and powder-activated concrete. Part I

Introduction. During the operation of buildings and structures, reinforced concrete structures are subject to various loads that can cause deformation and destruction. The strength and elastic-plastic properties, as well as the durability of modern concrete, are controlled using superplasticizers, nanoadditives, fillers, and aggregates. The potential of using nanohydrosilicate technologies is demonstrated. This article examines the physical and mechanical properties of cement stone and powder-activated concrete – one type of next-generation concrete. Materials and methods. The influence of the water/cement ratio, the presence of a carboxylate superplasticizer, and a modifying additive were considered as structure-forming factors for cement stone, and the influence of the water/cement ratio, modifying additive, superplasticizer, finely dispersed filler, rheological fillers and reactive fillers were considered for concrete. Results. The article presents the results of a study establishing the relationship between the density of cement stone and powder-activated concrete with the porosity and strength indicators under static and dynamic loads. The rational compositions of the developed composites are characterized by a set of improved physical and mechanical properties. It was found that an increase in the W/C ratio from 0.267 to 0.35 causes a decrease in the compressive and tensile strength of cement stone when splitting by 22–30%. The addition of the superplasticizer ”Melflux 1641F“ led to a significant decrease in the water-cement ratio – from 1.56 times compared to the composition of normal consistency and by 2.04 times – compared to the composition with an increased W/C ratio, as well as a corresponding increase in compressive strength properties – by 1.20 times and 1.72 times – in flexural tensile strength. Conclusion. It was found that the introduction of finely dispersed fillers into the composition of sand concrete led to an increase in compressive, flexural, and tensile strength when splitting by 1.62 to 2.55 times, which is explained by a denser packing of quartz filler, causing an increase in the density of such samples by 9.5%, the plasticizing effect of microquartz, and the high activity of microsilica. The impact strength of the cement composite was studied. It was found that plasticized highly filled compositions of the new generation demonstrated high values of the maximum contact force, contact duration, and impulse magnitude. The composite containing microquartz, quartz filler, fine aggregate, and Melflux 1641F superplasticizer has a maximum contact force of 4.530 N, compared to a similar value of 2.073 N for a cement stone composition made from normal consistency paste. Moreover, the contact duration and impact impulse magnitude are approximately twice as high. The addition of microsilica to the highly filled compositions caused even better results. The maximum contact force at which the samples failed was 4.530 N. This is more than twice that of cement paste based on normal consistency.