# Special Issue \"Reinforced Concrete: Materials, Physical Properties and Applications\"
## 10 Assessment on the Properties of Biomass-Aggregate Geopolymer Concrete  
The authors of the study [9] evaluate the properties of geopolymer concrete from biomass and aggregate. Part of the cement is replaced with crushed granulated blast-furnace slag and fly ash, and part of the aggregate is replaced with coconut shells in lightweight concrete. Through the use of recycled biomass aggregate (SBRAC), it is possible to achieve a reduction in thermal conductivity of more than 200% compared to concrete with natural aggregate and almost 20% than that of concrete with crushed coconut shell aggregate, respectively. The economic efficiency of the solutions proposed by the authors is also presented. Geopolymer concrete is a modern and relevant word in building materials science. Of particular relevance to this article is an interesting approach to the choice of raw materials. Research of Strength, Frost Resistance, Abrasion Resistance and Shrinkage in Steel Fiber Concrete for Rigid Highways and Airfields pavement Repair  
The authors of [10] conduct a study of the strength, frost resistance, abrasion resistance and shrinkage of steel fiber-reinforced concrete for the repair of hard pavements of roads and airfields. A comprehensive study of the effect of the amount of steel anchor fiber and hardening accelerator on the properties important for the repair of hard concrete pavement properties such as strength, frost resistance, wear resistance and shrinkage is carried out. The studied concretes contained 400 kg/m\({}^{3}\) of cement and polycarboxylate plasticizer in an amount of 1.2% of the cement content. It is established that concrete compositionswith the amount of hardening accelerator Sika Rapid 3 from 1 to 2% of the cement content and the amount of steel fiber from 60 to 90 kg/m\({}^{3}\) are optimal. At the estimated age, the compressive strength of fiber-reinforced concrete is 85-90 MPa, the bending strength is from 15.5 to 17.5 MPa, frost resistance is F200, and abrasion is not higher than 0.24 g/cm\({}^{2}\). Highways and airfields, due to their significant congestion and high degree of wear due to dynamic loads, require design, technological and recipe solutions. The authors present extremely interesting studies on the complex determination of a number of properties, and also offered the recipe and technological aspects of creating steel fiber concrete with a special application, namely in road and airfield pavements. This work deserves support and development in the direction of studying the applicability of such a material for even more critical road and airfield structures, as well as other structures with a similar operation pattern. The Influence of Composition and Recipe Dosage on the Strength Characteristics of New Geopolymer Concrete with the Use of Stone Flour  
The authors of the study [11] established the composition and dosage of the formulation influence on the strength characteristics of geopolymer concretes using stone flour. Analysis of setting time measurements showed that stone powder can accelerate the geopolymer composite curing. It is established that the addition of stone waste significantly increases the geopolymers compressive strength compared to a geopolymer composite containing only quartz sand. A microstructural geopolymer composite analysis is carried out, which confirms the effectiveness of the formulation technique implemented in this study. Geopolymer concrete with the use of stone flour proposed by the authors is a method illustrating an important direction in the development of the general theory of geopolymer concrete. This theory is currently not fully formed and is of a diverse nature, which differs significantly in its approaches in various scientific schools. However, the use of stone flour creates certain prerequisites for obtaining geopolymer concretes of a new generation.