Tensile fatigue behaviour of ultra-high performance fibre reinforced concrete (UHPFRC)

Abstract

The tensile fatigue behaviour of ultra-high performance fibre reinforced concrete (UHPFRC) under constant amplitude fatigue cycles is presented. Three series of uniaxial tensile fatigue tests up to a maximum of 10 million cycles were conducted with the objective to determine the endurance limit of UHPFRC that was supposed to exist for this material. The fatigue tests reveal that an endurance limit exists in all three domains of UHPFRC tensile behaviour at S-ratios ranging from 0.70 to 0.45 with S being the ratio of the maximum fatigue stress to the elastic limit strength of UHPFRC. Rather large variation in local specimen deformations indicates significant stress and deformation redistribution capacity of the UHPFRC bulk material enhancing the fatigue behaviour. The fatigue fracture surface of UHPFRC shows features of the fatigue fracture surfaces of steel, i.e. fatigue crack propagation is identified by a smooth surface while final fracture leads to rather rough surface. Various fatigue damaging mechanisms due to fretting and grinding as well as tribocorrosion are identified.

Ultra-High Performance Concrete: Mechanical Performance, Durability, Sustainability and Implementation Challenges

“…Before the failure point (95-100 % of the fatigue life), deformation increased rapidly again (Lappa et al 2004;Grunberg et al 2008). Under fatigue loading, fiber-reinforced UHPC specimens exhibited large variation in local deformations, indicating the ability of UHPC to redistribute stresses and strains, leading to enhanced fatigue behavior (Makita and Bruhwiler 2013). However, an increase in material global strain up to 1.6 % (strain hardening stage) decreased the deformation modulus from 39 to 10 GPa due to cracking of the UHPC matrix and fiber pull-out (Makita and Bruhwiler 2013).…”

“…Under fatigue loading, fiber-reinforced UHPC specimens exhibited large variation in local deformations, indicating the ability of UHPC to redistribute stresses and strains, leading to enhanced fatigue behavior (Makita and Bruhwiler 2013). However, an increase in material global strain up to 1.6 % (strain hardening stage) decreased the deformation modulus from 39 to 10 GPa due to cracking of the UHPC matrix and fiber pull-out (Makita and Bruhwiler 2013). Moreover, Lohaus and Elsmeier (2012), confirmed that UHPC with or without steel fibers exhibited fatigue life considerably higher than predictions of the CEB-FIP Model Code-90 (1993).…”

Tensile fatigue behaviour of Ultra-High Performance Fibre Reinforced Concrete combined with steel rebars (R-UHPFRC)

“…The fatigue endurance limit of monolithic UHPFRC is about 70% of the elastic limit strength [19] and average ratio of the elastic limit strength to the ultimate strength of all R-UHPFRC specimens is calculated to be 0.33. Accordingly, S = 0.23 is obtained as 70% of the average ratio of the elastic limit strength to the ultimate strength of R-UHPFRC.…”

“…In the early stage of the fatigue test, UHPFRC mainly carried fatigue stress and deformation behaviour of R-UHPFRC was strongly influenced by UHPFRC whose deformation was observed to grow under tensile fatigue [19]. This is why global deformation of R-UHPFRC increased in the early stage of the fatigue test.…”

“…Under tensile fatigue stress, local deformation of UHPFRC varied which is explained by variation of material properties of UHPFRC in the hardening domain [19] (Fig. 10).…”