Surface damages usually occur in concrete structures. In order to restore the functions and prolong the service life of concrete structures, their surface damages should be repaired in time. This paper reviews the main requirements for repair materials for concrete structures and the most used inorganic repair materials, such as cement-based materials, alkali-activated materials and polymer modified inorganic repair materials. Moreover, techniques to characterize and even improve the interfaces between these repair materials and concrete substrate are summarized. Cement-based material has the advantages of good mechanical properties and consistency with concrete substrate while having the problems of high shrinkage and low flexibility. Polymer modified materials were found as having lower shrinkage and higher flexural strength. Increasing the roughness or humidity of the surface, adding fibers and applying interfacial agents can improve the bond strength between cement-based repair materials and concrete substrates. All of these repair materials and techniques can help to build a good interfacial bonding, and mechanisms of how they improve the interface are discussed in this article. These are of great importance in guaranteeing the effectiveness of the repair of the concrete surface and to guide the research and development of new repair materials.

This paper presents data on the synthesis of cement grinding intensifiers produced from oil and gas processing wastes, namely secondary alkanolamines. The results of physicochemical characterization of the raw materials are reported, including the optimal purification conditions for the wastes and the synthesis parameters of the grinding intensifiers, as well as the physicochemical properties of the obtained products. It was found that the optimal conditions for producing the grinding intensifier involve conducting the reaction at 45°C for 6 hours with a 1:9 component ratio. The effects of the synthesized intensifiers on the cement clinker grinding process were investigated, including their influence on particle size distribution and the mineralogical composition of modified cements. The particles of the modified cement were shown to exhibit a predominantly spherical morphology; the maximum laser diffraction value reached 13.5%, the intensity was 88%, and the particle size was mainly around 2 μm (more than 53.5%), while the fraction of particles within the 100-200 μm range was 4.87%. X-ray diffraction and differential thermal analysis revealed that hydration of the modified cement is accompanied by a slight decrease in the diffraction intensity of calcium silicate phases (C2S and C3S), whereas an increase in the diffraction intensity of calcium hydroxide (Ca(OH)2) was observed. This indicates the formation of calcium hydroxide and calcium silicate hydrate (C-S-H) during cement hydration. The diffraction peaks of these phases were detected within the ranges of 30-33° 2θ and 40-45° 2θ. In addition, the presence of aluminate (C3A) and ferrite (C4AF) phases within 40-45° 2θ corresponds to calcium carbonate (CaCO3) observed in low-intensity regions between 29.4° 2θ and 48.5° 2θ, which is associated with CO2 absorption from the atmosphere. These changes reflect phase transformations during hydration and the formation of phases that are critical for strength development. The optimal dosage of the grinding intensifier in the cement composition was determined to be 0.02 wt.% (based on dry residue).

The present study investigates the combined influence of nano-ground quartz sand, microsilica, and a polycarboxylate-based modifier on phase evolution, microstructure development, and mechanical properties in low-clinker cement systems. The main objective is to evaluate whether finely dispersed quartz acts as an inert filler or contributes to hydration processes, and to determine the critical clinker threshold governing system performance. A hybrid modifier composed of microsilica and polycarboxylate (4:1) was introduced into a clinker–gypsum system together with varying amounts of nano-ground quartz sand. The mixtures were subjected to mechanical activation in a ball mill. Chemical composition, phase evolution, and microstructure were analyzed using XRF, XRD, and TEM, while mechanical properties were evaluated through standard tests. The results show that grinding duration and modifier dosage significantly influence particle dispersion and water demand. Optimal performance was achieved at 90 minutes of grinding and 6% modifier content. A nonlinear relationship between quartz content and compressive strength was observed, with a maximum value of 57.1 MPa obtained at 30% quartz and 55% clinker content. XRD analysis confirmed partial portlandite consumption and the formation of additional low-crystalline C–S–H gel, indicating a synergistic interaction between nano-quartz and microsilica. The results demonstrate that nano-ground quartz acts not only as a filler but also as a nucleation-active component with limited pozzolanic contribution. A further reduction in clinker content below 55% leads to insufficient formation of hydration products and a decline in mechanical performance, confirming the existence of a critical clinker threshold. These results provide a scientific basis for the design of low-clinker, low-carbon cementitious materials with enhanced performance.

Given the high energy intensity of the cement grinding process, the development of new and effective intensifiers is a pressing issue. The aim of this work is to develop grinding intensifiers from secondary raw materials produced during carpet manufacturing and gas processing wastes, and to study their effect on the structure and strength of modified cement stone. Methods of physicochemical analysis of raw materials and the obtained grinding intensifier, as well as standard methods for testing cement stone were used in the work. The possibility of obtaining an effective intensifier through the interaction of HYPAN (Hydrolyzed polyacrylonitrile) and diethanolamine was established. The optimal dosage of the grinding intensifier was determined to be 0.1%, which allows increasing the grade strength of modified cement stone by 31.2% and reducing the water consumption by 11%, which is explained by hydration due to the additional effect of reducing the electrokinetic potential between cement particles and increasing the fineness of cement particle grinding. Physicochemical analysis methods established that there is practically no free water in the modified cement stone sample and that the formation of the structure in the cement stone was achieved to a much greater extent. It has been established that, over time, the amount of C-S-H hydration products and calcium sulfoaluminate in the cement matrix of modified cement stone increases, which leads to an increase in the strength of the cement.