Effect of Fibers on Bond Performance of Lightweight Reinforced Concrete

Abstract

IntroductionIn construction industry lightweight concrete and fiber reinforced concrete are being used for many years. The former is known for brittle nature, light in weight and low thermal conductivity properties. It also offers better workability when compared to the normal weight concrete for the same slump value [1] These properties are affected by addition of discrete fibers; the effect being variable with the type and volume fraction of fibers [2].Use of steel fibers in structural concrete is particularly encouraged in members of structural system where geometrical constraints restrict use of traditional reinforcement. Guecna and Serna [3] suggest fiber reinforced concrete as a possible solution to shear failure problem in hollow core slabs where use of stirrups is challenging. High performance fiber reinforced cementitious composites having hardening behavior perform better as a strengthening material at serviceability and ultimate limits when compared to other strengthening techniques [4].Type of performance required from particular structural element usually governs the selection of fiber type and fiber content. Different fiber types, glass, steel, polypropylene, are being commercially produced and used for various applications. Since past few decades most of the research in concrete industry has been done on studying properties and behavior of different concretes, be it normal, high strength or lightweight, after fiber inclusion. For structural concrete used in load carrying members, steel fibers of different shapes and geometry are preferred over other fiber types due to their improved post cracking performance in flexure.Current experimental work encompasses the effect of steel fiber addition on bond strength of Lightweight Fiber Reinforced Concrete (LWFC); in addition to this, effect on other mechanical properties is also discussed. Integrity of a structural element is not ensured in the absence of proper bond between the reinforcement and the concrete surrounding it. It is now established, that the bond strength is influenced by different factors, categorized by structural, geometrical and material properties. ACI 408 [5] provides a good overview of these parameters. Many of the studies [6][7][8][9][10] have discussed some of these parameters

Bond of Reinforcement with Normal-weight Fiber Reinforced Concrete

“…Among these is the Normal-weight Fiber Reinforced Concrete (NWFC), which is developed after addition of fibers of various shapes and material. Effectiveness of fibers in crack control and for improving mechanical properties like flexural performance, bond, toughness and as an alternate to minimum shear reinforcement for concrete in highly congested reinforcing areas is already well acknowledged and reported [1][2][3][4]. Also in recent years tests on using steel fiber reinforced concrete as strengthening material have shown promising results [5,6].…”

Measurement and Utilization of Acoustic Emission for the Analysis and Monitoring of Concrete Slabs on the Subsoil

“…Another important aspect is a detailed knowledge of material properties from laboratory tests, like residual tensile strength [30][31][32][33][34][35], which can be determined according to [32,34]. Extra sensitive information concerning material properties namely includes fibre concrete strength in a single axis tension, fracture energy or stress-strain diagram.…”

Bond Performance of Deformed Rebar in Steel Fiber Reinforced Lightweight-Aggregate Concrete Affected by Multi-Factors

“…As the deformed rebar is popular used for the main reinforcement, the bond performance of deformed rebar in this new SFRLAC should also be reasonably evaluated. In this respect, the studies on bond properties of LAC dealt with expanded shale provide good references [15][16][17][18][19][20][21][22], and the enhancement of steel fibres on the bond of SFRLAC presents a bright prospect [23][24][25][26][27].…”

“…Regardless of types of coarse lightweight-aggregate used such as cold-bonded fly ash, expanded clay, oil palm shell and expanded shale aggregates, the addition of steel fiber enhances the bond strength of deformed rebar in SFRLAC. This may be due to the increased confinement effect which altered the failure mode from splitting to pull-out failure [23], the bridging effect of steel fiber which restrained the widening of cracks appeared on surface of SFRLAC to improve the splitting failure [24,25], or the strengthening effect which arrested the propagation of internal micro-cracks in pull-out failure [25]. The enhancements depend on the different conditions of concrete cover, rebar diameter, volume fraction of steel fiber and strength of SFRLAC.…”