Effect of elevated temperature on pull-out behaviour of 4DH/5DH hooked end steel fibres

Abstract

This paper presents the effect of elevated temperature on the bond mechanisms associated with the pull-out behaviour of steel fibres. A series of pull-out tests have been performed on 4D and 5D hooked end steel fibres embedded in four different types of concrete, namely, normal strength concrete (NSC), medium strength concrete (MSC), high strength concrete (HSC) and ultra-high performance mortar (UHPM). At the age of 90 days, the specimens were heated to target temperatures of 100, 200, 300, 400, 500, 600, 700 and 800°C respectively. The influence of elevated temperature on the mechanical and thermal properties of concrete was investigated. The results showed that the pull-out response of both fibres does not vary significantly throughout 20-400°C temperature range, but within the temperature range of 600 to 800°C, the pull-out strength decreases significantly for all concretes. The comparisons between the two fibre types show that the mechanical anchorage contribution provided by the 5DH fibre is significantly higher than that of the 4DH fibre, especially for higher strength concretes. The reduction in bond strength of both fibres after elevated temperature exposure is found to correlate closely with the degradation in compressive strength of the concretes.

Comparisons Between Pull-Out Behaviour of Various Hooked-End Fibres in Normal–High Strength Concretes

“…The high mechanical anchorage effect of these fibres was demonstrated in a number of prior studies showing that their strong bonding to the matrix resulted in a high resistance to pull-out (Abdallah and Fan 2017). Fibre with more a complex pre-deformed geometry place a higher complexity on the analysis of its pull-out response (Abdallah et al 2017c, d). As the number of hook bends increases, both the maximum pull-out load and pull-out work increase significantly.…”

“…The post-cracking behaviour of SFRC is closely related to the bond characteristics between the fibre and the matrix (Won et al 2013;Abdallah et al 2017c, d). The efficiency of fibres in bridging cracks depends upon the bond mechanisms associated with the pull-out behaviour (Islam and Alam 2013;Li and Liu 2016;Abdallah et al 2017b).…”

Dynamic Tensile Properties and Energy Dissipation of High-Strength Concrete after Exposure to Elevated Temperatures

“…Chemical explosions, gas explosions, and man-made explosions from terrorist attacks will lead some buildings to face fire and impact or explosion loads [4]. When concrete is subjected to fire, the residual mechanical properties can be seriously reduced by thermal damage due to internal physical and chemical changes, cracks, and deformations [5][6][7]. Although it has higher mechanical properties when compared with aggregate particles in the simulation is quite different from the actual aggregate shape, and this cannot fully demonstrate the tensile properties of concrete at high temperatures.…”

Active Reinforcing Fiber of Cementitious Materials Using Crimped NiTi SMA Fiber for Crack-Bridging and Pullout Resistance

“…Cementitious materials are good materials for civil construction with low cost and convenience for shaping. However, their low tensile strength and resulting cracking are critical drawbacks [ 1 , 2 , 3 , 4 ]. To overcome these problems, reinforcing fibers have been introduced as a solution, and some of them successfully raise the ductility and tensile strength of concrete/mortar and bridge cracks, thus delaying fracture [ 5 , 6 , 7 , 8 , 9 ].…”