Compressive strength behaviour of low- and medium-strength concrete specimens confined with carbon fibres in defective implementation conditions: an experimental study

Abstract

This behaviour of low-and medium-strength concrete specimens confined with carbon fibrereinforced polymer (CFRP) was analysed in three loading cycles. In some cases, stress levels were achieved that produced intemal microcracks, which allowed residual rigidity and the behaviour of completely microcraked concrete specimens to be studied. The specimens were subsequently tested to compression to the fracture point. Specimens reinforced in accordance with no manufacturing defects (100% CFRP reinforcement) and major manufacturing defects (50% CFRP reinforcement) were assessed for effectiveness and behaviour of the confined elements in less than ideal conditions. Results show that confinement was higher in lowresistance concretes, that the behaviour of reinforced specimens was unaffected by defective implementation conditions and that the reinforced specimens were less rigid than the non-reinforced specimens when tested up to 40% of ultimate fracture strength. RESUMEN: Estudio experimental del comportamiento a compresión de probetas de hormigón de resistencias bajas y medias confinadas con tejidos de fibras de carbono y con defectos muy importantes de ejecución.En este trabajo se estudia el comportamiento de hormigones de resistencias bajas y medias confinados con CFRP. Se han realizado 3 ciclos de carga llegando en algunos casos a niveles de tensión que han microfisurado internamente el hormigón, lo que ha permitido estudiar la rigidez residual y el comportamiento de probetas confinadas con el hormigón totalmente microfisurado. Posteriormente todas las probetas se han ensayado a compresión hasta rotura. Los refuerzos se han realizado con buenas condiciones de ejecución y simulando grandes defectos para poder evaluar la eficacia de los elementos confinados cuando las condiciones de ejecución no son las correctas. Los resultados muestran que el efecto de confinamiento es superior en hormigones poco resistentes, el comportamiento de las probetas reforzadas es poco sensible a grandes defectos de ejecución y su rigidez es inferior al de las probetas originales cuando se ensayan hasta el 40% de la tensión de rotura.

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“…Low unconfined concrete strength specimens were used mostly in experiments with CFRP confinement. Cánovas et al [29], Ilki et al [49], Li et al [51] and Shahawy et al [41] used low strength specimens. The lowest unconfined strength was 8.5 MPa and was used by Canovas et al [29].…”

“…Cánovas et al [29], Ilki et al [49], Li et al [51] and Shahawy et al [41] used low strength specimens. The lowest unconfined strength was 8.5 MPa and was used by Canovas et al [29]. The largest number of experiments utilized CFRP and GFRP wrapping with an unconfined strength that varies from 24 to 50 MPa [10,24,46,48,52].…”

Influence of the Modulus of Elasticity of CFRPs on the Compressive Behavior of Confined Test Pieces and on the Flexural Behavior of Short Concrete Beams

“…The performance of confined high-strength concretes has also been evaluated [52,53]. All cases have shown that the lower the strength of the confined concrete, the greater the benefits of confinement are [54][55][56]; that loading cycles reduce the rigidity of the element [57][58][59]; that large implementation defects only entail small decreases in strength [60]; and that the preload value of the element to be reinforced plays a very important role in the behavior of the reinforced element [61].…”

High strength oil palm shell concrete beams reinforced with steel fibres

“…Meanwhile past studies on fibre-reinforced concrete reported significant enhancement of the mechanical properties, cracking resistance and durability compared to the conventional concrete (3,7,8,(13)(14)(15)(16)(17)(18)(19). The other reported advantages of steel fibres in concrete include improving toughness (19), ductility (20), flexural behaviours (21) and impact and blast resistance (5).…”

“…Both the OPSFRC beams produced almost identical failure mode of failure, albeit HT30 beams produced smaller depth of flexural crack and concrete wedge. In fibre-reinforced concrete, the fibre improved the steel-concrete bonding by providing confinement effect which leads to the strain localization (18,28). The strain localization can be explained by using Fig.…”