Flexural and Interface Behaviors of Reinforced Concrete/Ultra-high Toughness Cementitious Composite (RC/UHTCC) Beams

Abstract

This paper presents an experimental investigation on the response of reinforced concrete (RC) beams with the use of ultra-high toughness cementitious composite (UHTCC) in the tension zone. Two parameters, the longitudinal reinforcement ratio and the depth of UHTCC layer, were varied. The failure mechanism, flexural behavior, interface performance, and cracking pattern were compared between RC and RC/UHTCC beams as well as between RC/UHTCC beams with different depths of the UHTCC layer. The experimental results revealed that the yielding load was improved apparently for beams with a reinforcement ratio of 0.67%, and the macro wide cracks in concrete turned into multiple tight cracks in the UHTCC layer depending on the prominent crack dispersion capacity of the UHTCC. However, RC/UHTCC beams with 1.0% and 1.73% reinforcement ratios showed shear-interface debonding failure prior to the yielding of reinforcement, and the failure resulted from the accumulated interface crack extension up to the support and the crush of concrete. Moreover, the theoretical analysis indicates that the interface cracking strength and ultimate interface bonding strength are related with the reinforcement ratio and UHTCC depth. The tensile stress difference of reinforcement in the UHTCC layer plays a controlling role in the interface debonding between concrete and UHTCC. The present study provides significant insights for the engineering application of hot-casting RC/UHTCC composite beam.

Enhancing flexural performance of ultra-high performance concrete by an optimized layered-structure concept

“…At the time of casting the top layer, the bottom layer was strong enough to support the top layer matrix, i.e. deformation of the layer interface was avoided; while the initial setting of the bottom layer matrix had not been reached [37,51], resulting in a strong interfacial bond. This casting method, on the one hand, induces to a sufficient layer bond strength; on the other hand, the existence of the layer interface can act as a source of micro-cracking, which consumes more fracture energy during the cracking process (this will be further explained in Section 4.3).…”

“…the thickness of the layer is randomly chosen and the influences of the layer thickness are not considered. Xu et al [36] and Hou et al [37] presented theoretical and experimental investigations on steel-bar reinforced concrete with an ultra-high flexural energy concrete (UHTCC) layer, in which effects of the reinforcement ratio and the layer thickness were discussed. It showed that the interface cracking and ultimate bonding strengths are related to the reinforcement ratio and UHTCC layer thickness.…”

Flexural behavior of two-layer reinforced concrete slab with hollow cores

“…22 The layer depth and the reinforcement ratio both have major effects on the bonding strength between the concrete layers. 23 The flexural strength of the two-layered beam increased nonlinearly with increasing layer thickness. 24,25 The compressive strength of a layered section is close to that of the weakest material in the section, and the layered section stiffness is the average of the values of the two materials used.…”

Flexural Performance of Composite RC Beams Having an ECC Layer at the Tension Face

“…Under the service load condition, it was found that the ECC layer prevented the migration of aggressive substances into the concrete. Further, experimental studies are reported on the performance of layered composite beams subjected to flexural loads [24][25][26]. The HPFRCC layer was provided at both the top and bottom faces of the beam, and their study concluded that the layer of HPFRCC at the bottom of the beam section was more effective than using it on the top of the section [24].…”