Sergii Kroviakov

This work investigates the composition of concrete for rigid pavements. The task addressed is to rapidly determine and technologically justify optimal concrete compositions taking into account various optimization criteria. An experiment was conducted in which the amount of cement, polypropylene fiber, and plasticizer varied. A set of experimental statistical models was constructed that reflect the influence of varied factors on the strength, wear resistance, and frost resistance of concrete. The cost of concrete and the value of the global warming potential (GWP) when manufacturing 1 m3 of concrete mix were calculated. The optimal concrete compositions have been determined using the constructed models by applying the step-by-step scanning of property fields. When scanning, a technologically justified step of changing the varied factors was adopted. The compositions that are optimal from an economic point of view, having the lowest cost, as well as the compositions that are optimal from an ecological point of view, having the lowest GWP level during manufacturing, were determined. The selected compositions have a compressive strength of at least 50 MPa, a tensile strength when bending at least 6.0 MPa, frost resistance not lower than F200, and abrasion resistance not higher than 0.40 g/cm2. The optimal composition from an economic point of view is characterized by a higher cement content and a small amount of fiber (0.3 kg/m3). The optimal composition from an ecological point of view has a 9.8% lower cement content and a higher fiber content – 2.6 kg/m3. The difference in the selected compositions is explained by the fact that cement is relatively inexpensive in the Ukrainian market, and the amount of fiber, due to its cost, significantly affects the cost of concrete. When using the determined optimal compositions in industrial settings, it is necessary to take into account differences in the quality of derived components for concrete mixtures, primarily cement and sand

The article examines the effect of Ukrainian-produced petroleum road bitumen BND 70/100 from Kremenchuk Oil Refinery modified separately with polymers, synthetic waxes, and adhesion additives on dense asphalt concrete type A, grade 1. Nine additives were studied: polymers (Calprene 501, PDL S501T SBS, Elvaloy 741, Kraton D1101 ASM), waxes (Asphalten A, Asphalten B, Sasobit) and adhesion agents (AdHebit LA-1245, Wetfix BE). Tests determined water saturation, density, compressive strength, deformation (0, 20, 50 °C), and Marshall properties at 60 °C. Polymer modifiers significantly improved strength, stiffness, temperature stability, and crack resistance. Waxes reduced water saturation and enhanced compaction but could lower low-temperature strength. Adhesion additives improved water resistance without notably increasing mechanical performance

This study investigates the properties of concrete incorporating recycled aggregates (RAs) for rigid pavement applications. A 15-point three-level experimental design was used to vary three composition factors: Portland cement substitution with fly ash (FA), and dosages of a superplasticizer (SP) and polypropylene fibers (PFs). A set of experimental–statistical models (ES models) was developed to predict the concrete strength, abrasion and frost resistance (FR), water absorption (WA), and global warming potential (GWP). This study aimed to develop a material that achieves both adequate mechanical performance for pavement applications and enhanced environmental sustainability by incorporating RAs and FA. The results demonstrate that replacing up to 13% of cement with FA does not compromise the splitting tensile strength or FR. For non-fibrous concrete, this substitution increases FR by approximately 50 freeze–thaw cycles. Application of PFs (2.4–3 kg/m³) enhances splitting tensile strength by 14–16% and improves FR by about 50 cycles. Using response surface methodology (RSM), optimal concrete compositions were identified that meet all target criteria: compressive strength ≥ 40 MPa, flexural strength ≥ 5 MPa, FR ≥ F200 (cycles), and abrasion resistance (AR) ≤ 0.5 g/cm², while simultaneously minimizing GWP. An additional optimum composition was determined by imposing a constraint on splitting tensile strength of ≥4.5 MPa. This graphical optimization approach, utilizing two-factor interaction diagrams, provides an effective and visual methodology for practical concrete mixture design. The novelty of the method lies in the discretization of the factor space, which enables efficient identification of optimal concrete mixture compositions.

Driving the circular economy in road construction requires the effective use of secondary materials like recycled concrete aggregate (RCA) and fly ash (FA). A key obstacle is the performance trade-off in concretes incorporating both materials. This research investigates feasible mix designs for road concrete, using RCA as a full gravel replacement and FA as a cement substitute. Polypropylene fiber (36 mm) and a superplasticizer were utilized to mitigate fresh and hardened state drawbacks. The experimental program included 15 modified mixtures with recycled aggregate and 3 control mixtures with natural aggregate. The workability of all concrete mixtures was kept constant at slump class S1. Road concretes with RCA, containing a 10–12% FA by cement replacement, at least 2 kg/m³ of polypropylene fiber (PF), and 4 kg/m³ of superplasticizer (SP), achieve compressive strength of at least 50 MPa and flexural strength of no less than 5 MPa at the design age. This performance is comparable to that of control mixtures. Furthermore, the abrasion resistance ranges between 0.48–0.50 g/cm², and the brittleness index falls within 0.095–0.100, significantly enhancing the durability of concrete for rigid pavement applications. The conducted cradle-to-gate life-cycle assessment (stages A1–A3) of the constituent materials for 1 m³ of concrete indicates the following environmental impacts: Global Warming Potential (GWP) of 195 kg CO₂ equation, Non-renewable Primary Energy Demand (PENRE) of 1140 MJ, Abiotic Depletion Potential for Fossil resources (ADPF) of 1120 MJ, Acidification Potential (AP) of 0.45 mol H⁺ equation, and Eutrophication Potential (EP) of 0.07 kg PO₄³⁻ equation It is established that the modified compositions not only meet the required performance criteria but also contribute to the goals of resource conservation in road construction.

Cross-beam glued-laminated timber (glulam) floor systems offer material efficiency but pose a complex design challenge due to three-dimensional (3D) load interactions, and systematic optimization guidelines are lacking. This study implements a parametric optimization framework using a three-factor Design of Experiments (DOE) approach (beam spacing ratio, height-to-span ratio, width-to-height ratio). A total of 27 full-factorial finite element models (FEMs) were simulated in Dlubal RFEM. A second-order response surface methodology (RSM) model was developed to predict the load utilization factor (Y) in accordance with Eurocode 5. The predictive model demonstrated high statistical accuracy (R² > 0.98). A multi-criteria optimization using the Pareto frontier identified a balanced solution (x₁ = 0.250, x₂ = 0.042, x₃ = 0.5) that achieved 97.4% load utilization (Y = 0.974). This optimal configuration reduces the required timber volume by approximately 10% compared with other efficient designs and by over 60% compared with inefficient (Y ≈ 0.5) but safe designs within the experimental space. The resulting regression model provides a validated engineering tool for designing materially efficient glulam floor systems, allowing designers to balance structural safety with material economy.

Introduction. The requisite strength, frost resistance, and abrasion resistance allow for a high operating life of concrete for rigid pavements. One of the effective methods to improve these physical and mechanical properties is dispersed reinforcement. However, under real economic conditions, it is important to evaluate the effectiveness of a specific type of dispersed reinforcement, considering its impact on the production cost of the material. The use of a set of experimental-statistical models, which are based on the results of the designed experiment, enables us to make a sound selection of optimal compositions of fibre-reinforced concrete for road pavement. Problems. The effectiveness of dispersed reinforcement significantly depends on concrete matrix properties influenced by the concrete’s composition, production technology, etc. The amount of dispersed reinforcement that provides the best increase in concrete strength is not always economically rational. Some requirements are imposed on road pavement concrete regarding strength, frost resistance, and abrasion resistance. Compliance with these requirements can be achieved through various designs of concrete mix and fibre-reinforced concrete, each with its own characteristics. Therefore, optimising the composition of fibre-reinforced concrete for rigid road pavements, taking into account modern material requirements and economic factors, is highly relevant. Aim. The optimisation of fibre-reinforced concrete composition that meets the requirements for the material of rigid road pavement for automobile roads of the category Ia and has a lower production cost. Results. The experiment was conducted according to an optimal plan. Three factors of the rigid road pavement fibre-reinforced concrete composition varied as follows: cement content from 300 kg/m³ to 380 kg/m³, polypropylene fibre content from 0 kg/m³ to 3.0 kg/m³, and lignosulfonate-based plasticiser content from 0.6 % to 1.0 % of the cement mass. The set of experimental-statistical models was computed. The models describe the influence of the varied factors on the concrete’s compressive strength, flexural tensile strength, frost resistance, abrasion resistance, and the cost of 1 m³. Using these models, the optimal composition of fibre-reinforced concrete was selected. The concrete meets the material requirements for category Ia road pavements and has the minimum cost. To implement the selection based on the set of experimental-statistical models, 17 two-factor «square» type diagrams were made with axes X2 (fibre quantity) and X3 (plasticiser quantity). The squares were built at 17 equal fixed levels of factor X1, corresponding to the entire range of cement quantity variation with a step of 5 kg/m³. Such discretisation allows for a more accurate and precise selection of an optimal solution. The fibre-reinforced concrete composition containing polypropylene fibre in 0.36 kg/m³ was selected. It is less than the amount that ensures the highest parameters of strength, frost resistance, and abrasion resistance. However, considering the specifics of how dispersed reinforcement functions within the concrete matrix and taking into account the market prices for concrete mix components, this particular composition is optimal.

The object of this study is concretes and fiber-reinforced concretes for rigid pavements with polypropylene fiber and lignosulphonate type plasticizer. The task addressed is obtaining concrete with increased strength and wear resistance. Three compositions factors were varied in the experiment conducted according to the D-optimal plan: the amount of cement (300–380 kg/m3), plasticizer based on lignosulfonates (0.6–1.0 %), polypropylene fiber with a fiber length 39 mm (0–3 kg/m3). All concrete mixtures had equal mobility S1. A set of experimental and statistical models was calculated. It was found that with an increase in the amount of plasticizer, the W/C ratio of the mixture decreases by 12–15 %, and the introduction of fiber has a negligible effect on W/C. Due to the use of fiber, the compressive strength of concrete at the design age increases by approximately 3.5 MPa, the early compressive strength practically does not change, the flexural strength increases by 0.5–0.6 MPa, and the abrasion resistance decreases by 0.07–0.08 g/cm2 (17–19 %). The most noticeable changes in these properties occur already with the introduction of fibers in the amount of 2–2.5 kg/m3. Increasing the amount of cement improves the strength and wear resistance of concrete, as well as the efficiency of using dispersed reinforcement. When the amount of plasticizer is increased from 0.6 to 0.9 %, the compressive strength of concrete at the age of 3 days increases by approximately 2 MPa; at the design age, its strength increases by approximately 5 MPa, the flexural strength increases to a limited extent while the abrasion of concrete decreases (wear resistance increases). Due to dispersed reinforcement and the use of a rational amount of plasticizer, concretes of rigid pavements with the required strength and increased wear resistance required for a given road category with reduced binder consumption were obtained, which could be used in practice