Steel fibers pull-out after exposure to high temperatures and its contribution to the residual mechanical behavior of high strength concrete

GONZALO RUANO; FACUNDO ISLA; BIBIANA LUCCIONI; RAÚL ZERBINO; GRACIELA GIACCIO

CONSTRUCTION AND BUILDING MATERIALS

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2018 vol. 163 p. 571 - 585

0950-0618

Many concrete structures are exposed to high temperatures that produce material deterioration involvingstiffness and strength loss. Although residual mechanical behavior of steel fiber reinforced concretesubjected to high temperatures has been studied in the last decades, the effect of the deterioration of eachcomponent of the composite behavior has not been assessed. This information together with a mesomechanicalmodel can be very useful for the design of steel fiber reinforced concrete to be used in structuresthat are expected to be exposed to high temperatures.This paper analyzes the effect of temperature on steel fibers pull-out mechanism from a high strengthconcrete matrix and its contribution to the residual mechanical behavior of Steel Fiber Reinforced HighStrength Concrete (SFRHSC). Pull-out tests of straight and hooked end fibers and uniaxial tension testson the fiber filaments exposed to room and high temperature (300 C, 375 C and 475 C) were performed.Additionally, two SFRHSC incorporating 30 kg/m3 and 60 kg/m3 of hooked end steel fibers anda plain High Strength Concrete (HSC) exposed to the same temperatures were studied. Uniaxial compressiontests and bending tests on notched prisms were used to characterize the composite material. Theexperimental results were analyzed with the aid of a pull-out model and a meso-model for SFRHSC, bothdeveloped by the authors. It is shown that hooked end fibers pull-out strength was reduced after theexposure to high temperatures. Since concrete strength only contributes in a small region surroundingthe hooks, the pull-out strength reduction can be mainly attributed to the reduction of steel strengthand frictional effects due to high temperature exposition. HSC tension strength reduction begins earlierand it is proportionally greater than pull-out strength reduction. As a consequence, HSC bending strengthdecreases faster than SFRHSC strength.