The paper presents the results of research into the efficiency of fine-grained concrete made using substandard materials and complex modifying admixture. The aim of the work is to evaluate the effect of multicomponent admixture on strength characteristics and efficiency of concrete. For this purpose the fractional factor experiment with variation of seven factors was applied, which were: microsilica, superplasticizers and other additives influencing both the properties of fine-grained concrete mixture and the properties of fine-grained concrete. The main criteria for assessing the influence of complex modifying admixtures were taken as the coefficient of structural quality and specific cement consumption per unit strength. The conducted research allowed to establish that the optimal composition of the additive increases the CQC by 29.9% and reduces the specific cement consumption by 24.6% in comparison with the control samples. It is shown that a balanced combination of additives improves the performance properties of concrete, contributing to resource saving and reducing the environmental load.

Keywords: fine-grained concrete, substandard materials, complex modifying admixture, structural quality coefficient, specific cement consumption, mathematical planning of the experiment, resource saving, compressive strength

In the article there was considered a possibility of off-grade materials utilization for making fine concrete with a multicomponent complex additive applied. Use of fine sands as raw material for fine concretes is actual for many regions in Russia because of deficiency of sands of necessary fineness modulus. There was considered the issue of utilization of fine sand and stale cement for reducing cost (loss), widening materials’ assortment for low-rise building, and energy- and resource-saving. To achieve the assigned purpose a multicomponent complex additive was applied. The research was carried out in full correspondence with the adopted design of the fractional factorial experiment. The acquired results were subject to a preliminary analysis and processing, and consequently dependences of strength properties upon varying factors were obtained. The obtained dependences made it possible to select optimal ingredients’ proportion of the complex modifying additive in order to increase strength properties of fine concrete based on off-grade materials. It was established that the use of optimal consumption of the complex additive components allows increase strength properties by 25-30% in comparison with the reference composition.

Keywords: fine concrete, fine sand, stale cement, complex additive, fractional factorial experiment, strength

metamaterials, microwave, antennas, diffraction, Maxwell equations, electromagnetic waves, the dielectric constant

Keywords: metamaterials, microwave, antennas, diffraction, Maxwell equations, electromagnetic waves, the dielectric constant