This paper discusses the influence of fiber orientation on elastic limit tensile stress of ultra-high performance fiber reinforced cementitious composites (UHPFRC). An original model relating elastic limit tensile stress to fiber orientation is proposed, and three determination methods of the elastic limit are compared. Five specimens are tested under uniaxial tension and characterized with digital image correlation, acoustic emission and displacement transducers. Before testing, the fiber distribution (local dosage and orientation) of each specimen is determined using a magnetic probe. After testing, three methods (offset with 2 different threshold values, and deformation modulus drop) are applied to determine the elastic limit tensile stress. The test results show that the proposed model estimates well the elastic limit tensile stress on the basis of fiber orientation. The modulus-drop method yields the most representative value for the elastic limit considering the underlying physical phenomena. It may be taken as definition of elastic limit tensile stress of UHPFRC.

The elastic limit tensile stress of UHPFRC is governed by contributions of the cementitious matrix and the fibrous skeleton. This paper finds that fiber orientation has significant influence on the matrix tensile strength of UHPFRC, while this is not considered in the estimation of elastic limit tensile stress. An original relation model between fiber orientation and the elastic limit tensile stress is proposed. Uniaxial tensile tests have been conducted on five dumbbell-shaped specimens, whose local fiber volume and orientation were determined using a magnetic probe before testing. Based on the measurement results of digital image correlation, acoustic emission and displacement transducers, the tensile response is characterized in detail. Based on the results of local fiber distribution, the influence of fiber orientation on the elastic limit tensile stress will be discussed, showing that the proposed relation model can well explain the variation of matrix tensile strength and estimate the elastic limit tensile stress of UHPFRC.

Ultra high performance fiber reinforced cementitious composites (UHPFRCs) have demonstrated their outstanding efficiency as structural materials. Determination of the bending resistance of members combining UHPFRC with steel reinforcement bars (R-UHPFRC) using material properties obtained by material testing gives satisfactory results. However, the synergetic interaction between rebar and UHPFRC in the tensile action due to bending, especially under loading-unloading of the structure is not yet well understood. This paper compared methods of analytical inverse analyses, as well as finite-element modeling and nondestructive testing (NDT), for determining UHPFRC material properties based on plates and R-UHPFRC members' test results. It was demonstrated that UHPFRC in the tensile zone of R-UHPFRC members can enter into compression during unloading, influencing the structural response under service loading.

This dataset is from an experimental campaign on 6 free and 6 restrained TSTM (Temperature Stress Testing Machine) specimen made of UHPFRC (Ultra High Performance Fiber Reinforced Concrete), subjected to partial and fully restrained conditions, under quasi-isothermal conditions at 20°C, performed by Mohamed Hafiz in the framework of his doctoral thesis. The development of autogenous shrinkage and corresponding eigenstresses under various degrees of restraint were studied for two types of mixes: Mix I with type I cement and silica fume and Mix II with silica fume and 50% mass replacement of type I cement with limestone filler. Amir Hajiesmaieli developed Mix II.

The article “An analytical inverse analysis to determine equi-biaxial tensile properties of strain-hardening UHPFRC from ringon-ring test”, written by Xiujiang Shen, Eugen Brühwiler, Emmanuel Denarié and Wanghu Peng was originally published electronically on the publisher’s.

PE-UHPFRC is a new Ultra High-Performance Fiber Reinforced Concrete (UHPFRC), which is developed to reduce the environmental impact of conventional UHPFRC by replacing the steel fibers with synthetic ones and reducing the clinker content in the mix. The development of the dynamic elastic modulus, the evolution of free autogenous deformations and the eigenstresses development with age, under full and partial restraint conditions, were investigated for PE-UHPFRC and the results were put into perspective with that for conventional UHPFRC with steel fibers. Furthermore, the tensile responses of different mixes under imposed shrinkage were compared and discussed. The results showed a shorter setting time and consequently an earlier initiation of elastic modulus development for PE-UHPFRC compared with that of conventional UHPFRC. Furthermore, the developed eigenstresses under full restraint conditions in a PE-UHPFRC layer compared with that for conventional UHPFRC were reduced by more than 70%, which is highly beneficial especially for cast-in-place rehabilitation applications.

A novel Ultra High-Performance Fiber Reinforced Concrete (UHPFRC) mix with synthetic fibers and a low clinker matrix, henceforth referred to as PE-UHPFRC, has been developed for structural applications. It exhibits a high tensile elastic limit above 7 MPa, a tensile strength of more than 10 MPa, and a very high tensile hardening domain of above 3.5%. In order to effectively use this material, its protective properties have been investigated on the basis of the effect of tensile deformation and subsequent cracking on water transport properties, for a wide range of tensile strain. A special setup was developed to measure the capillary absorption of liquids while the specimen is under tension. The results show a considerable reduction in capillary absorption in case of PE-UHPFRC compared with Strain Hardening Cement-based Composites (SHCC). Moreover, the results highlight the considerable effect of the onset of cracking on capillary absorption.

The article "An analytical inverse analysis to determine equi-biaxial tensile properties of strain-hardening UHPFRC from ringon-ring test", written by Xiujiang Shen, Eugen Bruhwiler, Emmanuel Denarie and Wanghu Peng was originally published electronically on the publisher's.

Ultra-High-Performance Fibre Reinforced Cementitious Composite (UHPFRC) provides solutions to enhance existing structures and design innovative new structures. Structural UHPFRC offers 3–5 times higher compressive and tensile strengths than ordinary concrete. Due to its strain-hardening behavior and dense matrix, structures made of UHPFRC remain crack-free and waterproof, guaranteeing durability. UHPFRC has been used particularly in Switzerland with more than 280 applications since 2003. A review of UHPFRC applications in the country is proposed in this paper. Ten bridge case studies are presented, including five strengthening of existing structures and five new designs. These structures were chosen to assess the multiple benefits that UHPFRC provides compared to traditional reinforced-concrete structures. Besides structural efficiency, several construction criteria are considered, such as construction costs, material durability, environmental impacts, and construction time. Structural rehabilitation made with UHPFRC leads to cost-effective interventions, and this material also helps to preserve heritage structures. Due to its specific mechanical properties, UHPFRC enables new structures with distinctive aesthetic designs with reduced construction time. The crucial contribution of research to the first case studies is also highlighted. This link between Swiss universities and the construction industry has quickly transitioned UHPFRC Technology from academic studies to real-world applications. Nowadays, the UHPFRC Technology is maturing and applications are common in the country.

Proportioning the dosage of Ground Calcium Carbonates (GCC) in cementitious materials, beyond current normative levels, is one of the most promising ways towards sustainability of mortar and concrete technology. Performance parameters such as the water/binder ratio do not represent the very significant benefits in terms of mechanical performances, of clinker replacement by GCC in mixes with water/cement ratios in the range of that for normal concretes used in construction (0.4 to 0.6). Alternative parameters such as the water/fines ratio proved to be reliable indicator of performances for Ultra High-Performance Fiber Reinforced Concretes. This concept needs to be further extended to normal concretes, on a scientific basis. With this aim in view, mortar mixes with a similar water/cement ratio of 0.5 and progressive replacement of sand by GCC with water/fines ratios as low as 0.2 were studied. The packing density of the cement and GCC was determined by means of wet packing measurements using the mixing power method. The Compressible Interaction Packing Model from Fennis was generalized to multiple polydisperse components and used to predict the packing density of the mixes. The rheology at fresh state of the mixes was put into perspective with the packing density, water film thickness and sand packing factor to define reliable indicators of performances at fresh states. Finally, the compressive strength of the mixes at 1 and 28 days was related to the efficiency coefficient of the GCC used.

This paper addresses the uniaxial tensile response of Strain Hardening Ultra High-Performance Fiber Reinforced Concretes (SH-UHPFRC) subjected to very low strain rates and low temperatures. The influence of four different strain rates; 1 x 10(-5),1 x 10(-7),1 x 10(-8) and 5 x 10(-9) 1/s on the tensile properties like elastic limit, elastic modulus, tensile strength and the strain at tensile strength, was studied for two types of SH-UHPFRC mixes; Mix I with type I cement and silica fume, and Mix II with silica fume and 50% mass replacement of type I cement with limestone filler, at three curing temperatures; 20 degrees C, 10 degrees C and 5 degrees C. The tests at strain rates lesser than 1 x 10(-6) 1/s are the first of their kind for UHPFRC materials and the results show a considerable impact on the elastic limit of the mixes. Acoustic Emission tests were also carried out for validation of test results of the elastic limit.

The equi-biaxial tensile properties of strain-hardening UHPFRC are determined and investigated based on an original analytical inverse analysis of results from ring-on-ring tests. First, the analytical inverse analysis method is developed based on the elastic slab bending and yield line theories. Using this method, a new objective criterion for the determination of the elastic limit stress of strain-hardening UHPFRC is provided, and a point-by-point inverse analysis is used to obtain the strain value at the end of hardening. This method reduces uncertainties regarding assumptions and avoids any iterative procedures. The inverse analysis results are put into perspective with experimental evidence, particularly based on DIC measurements. Moreover, the uniaxial tensile properties are also derived from the inverse analysis of 4PBT results and compared with the equi-biaxial tensile properties from the proposed inverse analysis. The inverse analysis results show a 18% lower elastic limit stress, and almost equivalent tensile strength of UHPFRC subjected to equi-biaxial stresses, compared with the corresponding values from uniaxial stress. Moreover, a relatively small equi-biaxial strain at the end of hardening is highlighted.

The tensile behavior under low loading rates governs to a large extend the mechanical response of Strain Hardening Ultra High Performance Fiber Reinforced Concretes (SH-UHPFRC) at early age and long term, in applications of rehabilitation. A viscoelastic-viscohardening model was developed and applied to predict the tensile response of two types of SH-UHPFRC; Mix I with pure type I cement, silica fume and steel fibers and Mix II with 50% replacement of cement with limestone filler and a similar fibrous mix, and compare their time dependent performance. Different tensile loading conditions were investigated, including the behavior under restrained shrinkage deformations, the effect of very low monotonic strain rates, and linear and non-linear relaxation and creep tests. The predictions of the model were also compared with experimental results from literature. The interaction of ageing, hydration, early age volume changes, viscoelastic phenomena and damage and their influence on the overall tensile behavior of UHPFRC was discussed. (C) 2020 Elsevier Ltd. All rights reserved.

(PE)-UHPFRC, a novel strain hardening ultra high-performance fiber reinforced concrete (UHPFRC) with low clinker content, using Ultra-High Molecular Weight Polyethylene (UHMW-PE) fibers, was developed for structural applications of rehabilitation. A comprehensive life cycle assessment (LCA) was carried out to study the environmental impact of interventions on an existing bridge using PE-UHPFRC compared with conventional UHPFRC and post-tensioned reinforced concrete methods in three categories of global warming potential (GWP), cumulative energy demand (CED), and ecological scarcity (UBP). The results showed 55% and 29% decreases in the environmental impact of the PE-UHPFRC compared with reinforced concrete and conventional UHPFRC methods, respectively, which highlighted the effectiveness of this material for the rehabilitation/strengthening of structures from the viewpoint of environmental impact.

The tensile response of strain hardening UHPFRC under full restraint, subjected to curing temperatures of 20 degrees C, 10 degrees C, 5 degrees C, was investigated for two types of mixes with silica fume; Mix I with pure type I cement and Mix II with 50% replacement of cement with limestone filler, both having a similar steel fibrous mix. The development of the elastic modulus, tensile strength, autogenous shrinkage and eigenstresses were put into perspective with the hydration kinetics. Two phases of pozzolanic reaction with different rates of consumption of silica fume were identified. A systematic increase of the autogenous shrinkage and eigenstresses with the curing temperatures was observed. The eigenstresses development was much slower in the case of Mix II, owing to its larger relaxation potential. The eigenstresses in Mix I reached the strain hardening domain after one month, whereas the same in Mix II were only approaching the strain hardening domain after three months.

This paper addresses the tensile response of Strain Hardening Ultra High Performance Fiber Reinforced Concretes (SH-UHPFRC) subjected to restrained autogenous shrinkage deformations under full and partial restraint conditions, right after casting and until one month. The development of autogenous shrinkage and corresponding eigenstresses under various degrees of restraint were studied for two types of mixes; Mix I with type I cement and silica fume, and Mix II with silica fume and 50% mass replacement of type I cement with limestone filler. The tests under 100% restraint conditions are the first of their kind on SH-UHPFRC and the results show that under these conditions, the material enters into the strain-hardening domain of the tensile response. The development of eigenstresses was much slower in the Mix II when compared to that of Mix I. The development of the dynamic elastic modulus and heat of hydration were also studied and put into perspective.

Offshore lighthouses are a remarkable historical heritage often over 100 years old. The management of their ageing is a challenge and requires a thorough understanding of their structural response under wave loading. With this aim in view, the dynamic response of the 'La Jument' lighthouse in the French Iroise Sea was characterized in situ, with accelerometers, under the action of a breaking wave, during a winter storm in January 2018. Detailed exploitation of the measurement data complemented by photographic documentation of the same wave event helped determine eigenfrequencies and damping coefficients of the structure as well as the likely orientation of the wave and the position of its crest with respect to the lighthouse tower. The results of these analyses were put into perspective with those of literature and more specifically from three-dimensional finite element modelling of the structural response of the lighthouse under the action effects of breaking waves. This article is part of the theme issue 'Environmental loading of heritage structures'.

The hydration of an ultra-high performance fibre reinforced concrete (UHPFRC) paste with a water to cement ratio of 0.18 was followed by proton nuclear magnetic resonance (1H NMR) alongside more classical techniques for hydration kinetics, and microstructural analysis. The states of water were quantified at different times by following the repartition of the “mixing water” after casting into “capillary water, gel water, CSH interlayer water and solid water” as hydration takes place. It was found that the capillary water is quickly depleted, and subsequently hydration continues with the consumption of the gel water. Overall the material becomes extremely self-desiccated with all water, bound in crystalline hydrates and the interlayer of C-S-H.

Ultra-high performance fiber reinforced concretes (UHPFRC) have demonstrated their potential to contain the explosion of maintenance costs (Economy and Environment) for civil engineering structures, due to their extremely low permeability associated with the outstanding mechanical properties. Substitution of embodied-energy (EE)-costly components of UHPFRC such as clinker and steel fibers, is the next step towards sustainability, to make it even more efficient and more environment-friendly. In this study, a strain hardening UHPFRC mix with two main modifications has been developed in which (1) 75% of steel fibers have been replaced by ultra-high molecular weight polyethylene (UHMWPE, henceforth referred to as PE) fibers and (2) 50% volume of cement type CEM I have been replaced with limestone filler. The effect of the fiber orientation and the specimen thickness on the mechanical properties of such mixes have been investigated. The mechanical properties have been investigated using direct tensile test, and 4-point bending test. Finally, the dramatic effect of fiber orientation on the ultimate strength and deformability has been demonstrated. Moreover, the results confirm that the specimen thickness affects the deformation capacity of the specimens. Finally, improvements in terms of reduction of EE of the proposed mixes, are highlighted.

Strain Hardening Ultra High Performance Fiber Reinforced Concretes (SH-UHPFRC) have a high elastic limit (around 10 MPa) and high tensile strength (upto 20 MPa) and exhibit significant strain hardening (1 to 4 %) under tensile loads. These appealing features make them extremely effective materials for strengthening and improving the durability of existing structures. However, their cast on site application induces significant eigenstresses due to restraint conditions. In this paper, the effects of various restraint conditions on the tensile viscous response of SH-UHPFRC was determined experimentally using a Temperature Stress Testing Machine and was modelled. Tests were done at partial and full restraint conditions to study the eigenstresses development. The ageing linear viscoelastic response of the material was modeled using an ageing generalized Maxwell model, fitted on the experimental data of eigenstresses. The influence of the scatter of free shrinkage measurements on the model prediction was studied through a sensitivity analysis.