Search for optimal compositions of fiber-reinforced concrete for rigid pavement using experimental statistical models

The experiment was conducted according to a 15-point plan. In the experiment, the following three factors of the composition of rigid pavement fiber-reinforced concrete varied: the amount of Portland cement from 290 to 350 kg/m3, the amount of basaltic fiber from 0.9 to 1.5 kg/m3, the amount of superplasticizer from 0.6 to 1% of the cement mass. A set of experimental statistical models was obtained. They describe the influence of factors on compressive strength, flexural strength, frost resistance, abrasion resistance and cost of fiber-reinforced concrete. The selection of optimal compositions of fiber-reinforced concrete rigid pavement for the roads of II-III and Ib categories was carried out using these models. The selection of optimal compositions of fiber-reinforced concrete was carried out graphically using square diagrams. The method of representing the factor space as 7 "square" type diagrams was used when fixing the amount of cement in the composition from 290 to 350 kg/m3 with a step of 10 kg/m3. This discretization allows for a clearer and more accurate search for optimal solutions. The levels of compressive strength, flexural strength and frost resistance were used as limitation criteria. These levels meet the requirements of DBN B.2.3-4:2015 for rigid pavement materials of the corresponding category. The concrete cost index was used as an optimization criterion. The abrasion resistance of concrete was also controlled to guarantee a correct choice. Two compositions of fiber-reinforced concrete for the roads of the II and III categories were chosen. These compositions have a compressive strength of 43 and 45 MPa, a flexural strength of 5 and 5.1 MPa, abrasion of about 0.36 g/cm2 and frost resistance of F200. Two compositions of fiber-reinforced concrete for category Ib roads were also selected. These compositions have a compressive strength of 48 and 50 MPa, a flexural strength of 5.5 MPa, abrasion of about 0.35 g/cm2 and frost resistance of F200. The compositions have chosen the lowest cost price while ensuring the strength and durability of the material. The use of this fiber-reinforced concrete makes it possible to increase the intervals between repairs during the maintenance of cement concrete roads in typical climatic conditions in Ukraine.