Steel Reinforced Self-Compacting Concrete (SCC) Cantilever Beams: Bond Behaviour in Poor Condition Zones

Abstract

Previous investigations carried out on reinforced self-compacted concrete (SCC) beams have reported contradictory results on reinforcement bond behaviour occurring in the zones defined for good bond conditions according to Eurocode2. Cantilevered SCC beams’ critical upper tension reinforcement bond behaviour has previously had limited reporting. In this study, the bond behaviour in normally vibrated concrete (NVC) and self-compacted concrete (SCC) in poor conditions zones are compared and the differences are highlighted. The effect of four parameters, including (i) concrete type (SCC and NVC), (ii) characteristic strength of SCC, (iii) lap splice length, and (iv) depth of concrete cover for the reinforcement is investigated. It was found that for the studied beams, increasing splice length improved the energy absorption and changed the failure mode to a more ductile manner even at the poor bond conditions zones. The maximum measured steel strains in SCC beams in the lap splice zones, were higher than those for NVC specimens. The mean bond stress values, for SCC beams with 25–50% lap splice lengths, were higher than those of NVC beams, with the same lap splice lengths, by 16–13%, respectively. The results of the current study showed that the empirical equations from the literature overestimated the bond strength of the splice lap length for cantilever upper steel in SCC beams with long splices which agrees with the state of the art as these equations were developed originally for short anchorage lengths.

Mechanical Properties of High-Strength Self-Compacting Concrete

“…The use of superplasticizers and viscosity-modifying admixtures allows for a high-volume fraction of fine particles and fibers to be incorporated into the mix, resulting in a highly dense and homogeneous microstructure. In contrast, high-strength NVC is typically produced using a low water-to-cement ratio and a higher cement content, resulting in a highly dense and compact microstructure. , …”

“…In contrast, highstrength NVC is typically produced using a low water-tocement ratio and a higher cement content, resulting in a highly dense and compact microstructure. 16,17 In this study, we aim to contribute to the current body of knowledge on the mechanical properties of HSSCC by investigating its stress−strain characteristics, elastic modulus, and Poisson's ratio. Three mixes are selected with compressive strengths of 70, 80, and 90, and cylindrical specimens are cast and tested to determine the stress−strain characteristics of each mix.…”

“…In contrast, high-strength NVC is typically produced using a low water-to-cement ratio and a higher cement content, resulting in a highly dense and compact microstructure. 16 , 17 …”

Experimental Study on Two-Step Concrete Corbels with Several Interface Conditions

“…The bond strength of the interface is controlled by several parameters such as the substrate roughness degree, curing conditions, material strength and stiffness of both concrete layers, and the implanted steel reinforcement crossing the interface and its anchorage [17,[24][25][26][27]. The concerns related to such issue are not only related to static loading, but also the dynamic loads and several precasting conditions can critically generate adverse and noncontributable stresses on such RC element [28][29][30].…”