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.
Conclusion. Using the set of experimental-statistical models, the graphic method selects the optimal composition of fibre-reinforced concrete for rigid pavement. The composition guarantees required strength, frost resistance, and abrasion resistance for the category Ia road pavement and has minimal cost.
