UHPFRC for the cast-in place reinforcement of offshore maritime signalization structures

[EN] Offshore lighthouses are a remarkable historical heritage often over 100 years old. The management of their aging is a challenge. The extremely low permeability of Ultra-HighPerformance Fiber Reinforced Concretes (UHPFRC), combined with their outstanding mechanical properties (robust tensile Strain Hardening (SH) for specific mixes) are particularly suitable for the reinforcement of this type of structures and more generally offshore maritime signalization structures. These structures under the influence of tides and weather, exposed to a very aggressive environment, have very limited access. As for existing bridges, SH-UHPFRC provide in this case a robust, effective, and very durable reinforcement solution, making it possible to simplify and reduce the duration of interventions. In this context, an existing turret at sea, on the south coast of Brittany, was reinforced by the application of a 60 mm UHPFRC hull, cast in place by helicopter in a formwork around the existing masonry structure. This application paves the way for the reinforcement with the same materials of lighthouses at sea exposed to extreme weathering conditions, such as "La Jument" nearby the island of Ushant (Brittany, France).Denarié, E. (2018). UHPFRC for the cast-in place reinforcement of offshore maritime signalization structures. En HAC 2018. V Congreso Iberoamericano de hormigón autocompactable y hormigones especiales. Editorial Universitat Politècnica de València. 17-30. https://doi.org/10.4995/HAC2018.2018.8261OCS173

Structural behaviour of hybrid elements with Advanced Cementitious Materials (HPFRCC)

Advanced Cementitious Materials such as HPFRCC are well adapted for durable repair and strengthening of concrete structures. Experimental and numerical investigations have been conducted to study the behavior of hybrid structural elements consisting of HPFRCC and ordinary concrete. The behavior at service state as well as at ultimate limit state of the beams reinforced with HPFRCC was comparable or better than the behavior of the beams reinforced with ordinary reinforced concrete. The sensitivity of numerical models for hardening materials such as HPFRCC was demonstrated

ARCHE D06 - Recommendations for the tailoring of UHPFRC recipes for rehabilitation

The extremely low permeability of Ultra High Performance Fibre Reinforced Concretes (UHPFRC) associated to their outstanding mechanical properties make them especially suitable to locally "harden" reinforced concrete structures in critical zones subjected to an aggressive environment and to significant mechanical stresses. UHPFRC provide a unique and robust solution to simplify the construction process, dramatically reduce the duration of sites, and save money with long term durability. Rehabilitations, especially with cast on site UHPFRC are among the most demanding applications for those materials and require a significant strain hardening response under tension. Achievement of tensile strain hardening, extremely low permeability and self-compacting character is indeed a challenge that few current UHPFRC recipes can satisfy. Cement-superplasticisers compatibility issues severely restrict the range of possibilities to develop new UHPFRC recipes based on locally available components with the required properties for cast in situ applications. An original concept of Ultra High Performance matrix has been developed that makes the application of UHPFRC technology feasible with a wide range of cements and superplasticisers, with outstanding mechanical and protective performance, without significant loss of workability. This concept is an extension to UHPFRC materials of the concepts of cements blended with Limestone fillers, already applied successfully to a wide range of normal or high performance concretes. In a further step, the rheology of those mixes has been adapted to enable them to support challenging 5 % slopes of the substrates at fresh state. The development of this new technology and its portability in various countries opens very promising perspectives for the dissemination of this concept not only for rehabilitation but also for various applications of UHPFRC, prefabricated or cast-in-situ. This document presents both a general methodology for the tailoring of UHPFRC recipes (fibrous mix and matrix) and its application to Slovene and Polish components

SAMARIS D25b - Guidance for the use of UHPFRC for rehabilitation of concrete highway structures

order to manage structures effectively and to reduce this burden to the minimum, the number and extent of interventions have to be kept to the lowest possible level. The extremely low permeability of Ultra-High Performance Fibre Reinforced Concretes (UHPFRC) associated with their outstanding mechanical properties make them especially suitable to locally "harden" reinforced concrete structures in critical zones subjected to an aggressive environment and to significant mechanical stresses. Composite UHPFRC-concrete structures promise a long-term durability which helps avoid multiple interventions on structures during their service life. UHPFRC materials can be applied on new structures, or on existing ones for reha-bilitation, as thin watertight overlays in replacement of waterproofing membranes, as rein-forcement layers combined with reinforcement bars, or as prefabricated elements such as kerbs. This document gives an overview of the conceptual approach, and provides basic guid-ance in view of the application of UHPFRC for the rehabilitation of reinforced concrete structures

Essais de caractérisation - réponse en traction

Le comportement en traction des BFUP (résistance élevée et déformabilité notable) est un de leurs principaux attraits. Pour valoriser au mieux ces propriétés, il importe de disposer d’essais et de méthode d’analyse inverse permettant de déterminer la réponse en traction des BFUP soit directement au moyen d’essais de traction uniaxiale, soit indirectement au moyen d’essais de flexion sur bandes minces. Dans un premier temps on présente les deux types d’essais proposés pour caractériser la réponse en traction des BFUP : traction uniaxiale sur éprouvettes cintrées non entaillées et flexion 4 points sur bandes non entaillées et les paramètres qui en sont extraits. Dans un deuxième temps on illustre l’analyse des résultats d’essais au moyen d’exemples d’application basés sur le cas de chantiers récents

UHPFRC tensile creep at early age

Ultra high performance fibre reinforced concrete (UHPFRC) early age viscoelastic behaviour under tension was investigated. The tests results showed a high creep potential due to the high volume paste (88%). This result is of major importance because the viscoelastic properties contribute to mitigating the high early age stresses generated under restrained shrinkage. This beneficial effect was reflected by the increased linear-relationship between tensile creep and shrinkage. As expected, UHPFRC tensile creep behaviour was also sensitive to the loading level. Above 35% of the tensile strength at the loading age, the material exhibited viscoplastic behaviour. A Maxwell chain model was applied to predict the early age UHPFRC tensile creep and confirms the induced non-linear respons

Evaluation of UHPFRC activation energy using empirical models

The influence of thermal curing on the evolution of the material properties and the UHPFRC behaviour was investigated. Tests results showed a beneficial effect of a high temperature curing on the early age material properties due to the thermo-activation effect on the hydration process. However, an inverse effect was observed at long-term. In our study, activation energy of UHPFRC was evaluated from experimental data by means of empirical models. The traditional maturity-function based on Arrhenius law, generally used to describe thermally activated physical or chemical processes, was used to predict the evolution of the UHPFRC autogenous shrinkage and to validate the applicability of this concept for such cement-based materials. Results showed that the concept based on Arrhenius law could describe correctly temperature effects on UHPFRC for temperature lower than 30°

SAMARIS D22 - Full scale application of UHPFRC for the rehabilitation of bridges – from the lab to the field

The premature deterioration of reinforced concrete structures is a heavy burden for society. In order to manage structures effectively and to reduce this burden to the minimum, the number and extent of interventions have to be kept to the lowest possible level. The extremely low permeability of Ultra-High Performance Fibre Reinforced Concretes (UHPFRC) associated with their outstanding mechanical properties make them especially suitable to locally "harden" reinforced concrete structures in critical zones subjected to an aggressive environment and to significant mechanical stresses. Composite UHPFRC-concrete structures promise a long-term durability which helps avoid multiple interventions on structures during their service life. UHPFRC materials can be applied on new structures, or on existing ones for rehabilitation, as thin watertight overlays in replacement of waterproofing membranes, as reinforcement layers combined with reinforcement bars, or as prefabricated elements such as kerbs. This document gives an overview of the conceptual approach, and provides detailed informations on the first application performed during the European project SAMARIS (Sustainable and Advanced MAterials for Road InfraStructures), in view of the application of UHPFRC for the rehabilitation of reinforced concrete structures