INFLUENCE OF FIBER ON INCREASE OF CRACK RESISTANCE OF REINFORCED CONCRETE STRUCTURES

One of the most widely used materials in almost allfields of construction is concrete. However, alongsideits advantages, concrete is characterized by low impactstrength, low tensile strength, and the formation ofshrinkage cracks during hardening. To increase thestrength of concrete, prevent the appearance of cracks,and improve other characteristics of concrete (resistanceto vibration and impact loads, etc.), various types offibers are introduced into the concrete mix.As a result of the conducted research, it was foundthat the plastic strength of cement paste with fiberincreased several times compared to the compositionwithout fiber. At the same time, the increase in tensilestrength of concrete under bending with the use ofcoarse aggregate and various types of fiber is notsignificant. The slight positive effect of fiber in concreteswith coarse aggregates compared to cement paste canbe explained by the neutralization of this effect dueto the use of coarse aggregate, the grain size of whichcan be compared with the fiber length. Therefore, itis advisable to use fiber-containing concretes with fineaggregate.It was found that the introduction of fiber into theconcrete mix significantly reduces its shrinkage. Theshrinkage of fiber-containing concrete, compared toconcrete without fiber, in the early stages of hardeningis 3-4 times less. The shrinkage of the concrete controlsamples is 0.23 mm/m, while for concrete with fiber, it is0.075 mm/m. Thus, the introduction of basalt fiber intothe concrete mix, reducing the shrinkage deformationsof concrete in the early stages of hardening, respectivelyincreases the crack resistance of reinforced concretestructures. Over time, this fine basalt fiber dissolves,but the concrete gains strength, compensating for theabsence of the dissolved fiber. Thus, its high crackresistance is maintained. The obtained results formthe basis for optimizing technological solutions forconcreting structures in terms of section sizes.It is shown that one of the cheapest types of fiberis basalt fiber, obtained from molten rocks like basalt.Basalt fibers do not release toxic substances into theair and wastewater and do not form toxic compoundsin the presence of other substances. Basalt fiber hashigh physical and mechanical characteristics and a lowthermal conductivity coefficient.It is shown that the effectiveness of fiber introductiondepends on the concrete composition. To achieve themaximum "strength" effect from fiber introduction, it ismost advisable to use fine-grained concretes.It is known that "fine" basalt fiber dissolves overtime in hardening concrete. It retains its propertiesin concrete when the fiber diameter is more than 80microns.It was found that dispersed reinforcement with basaltfibers reduces the formation of shrinkage cracks inconcrete containing coarse aggregate, even at the stagewhen the concrete is in a plastic state.The introduction of basalt fiber into the concrete mix,reducing the shrinkage deformations of concrete in theearly stages of hardening, respectively increases thecrack resistance of reinforced concrete structures. Overtime, this fine basalt fiber dissolves, but the concretegains strength, compensating for the absence of thedissolved fiber. Thus, its crack resistance is maintained.The obtained results form the basis for optimizingtechnological solutions for concreting structures interms of section sizes.