E. Denarié

Experimental Investigation of Composite Ultra-High-Performance Fiber-Reinforced Concrete and Conventional Concrete Members

Composite ultra-high-performance fiber-reinforced concrete (UHPFRC) and conventional reinforced concrete structural members are investigated to assess the rehabilitation potential for existing concrete structures. The composite structural response is determined by testing 12 full-sized flexural beams, loading the UHPFRC layer in tension. The results demonstrate that the exceptional material properties of UHPFRC significantly improve the composite member structural response, including the ultimate force, stiffness, and cracking behavior. An analytical model is developed to predict the composite UHPFRC and conventional reinforced concrete structural response, and is employed to further analyze the experimental test results.

Rehabilitation and Strengthening of Concrete Structures Using Ultra-High Performance Fibre Reinforced Concrete

Abstract An original concept is presented for the durable rehabilitation and strengthening of concrete structures. The main idea is to use ultra-high performance fibre reinforced concrete (UHPFRC) complemented with steel reinforcing bars to protect and strengthen those zones of the structure that are exposed to severe environmental influences and high mechanical loading. This concept efficiently combines the protection and resistance properties of UHPFRC and significantly improves the structural performance of the rehabilitated concrete structure in terms of durability. The concept has been validated by means of field applications, demonstrating that the technology of UHPFRC is now well developed for cast in situ and prefabrication using standard equipment for concrete manufacturing. This novel technology is a step forward towards more sustainable structures.

Thermal Effects on Physico-Mechanical Properties of Ultra-High-Performance Fiber-Reinforced Concrete

Material characterization tests of an Ultra High Performance Fiber Reinforced Concrete (UHPFRC) were performed at various ages. A linear relationship was obtained between the mechanical properties and the degree of hydration. In parallel, the influence of curing conditions on the physico-mechanical properties and the time dependent behavior of this UHPFRC was investigated. A temperature increase accelerated the hydration process at early age and therefore improved the material’s compressive strength and the carrying capacity in four point bending tests, but at a long term, a higher temperature had inverse effects on the mechanical properties. Moreover, at a 20 °C temperature cure, the UHPFRC exhibited autogenous shrinkage at long term comparable to normal concrete. An increase of curing temperature increased the autogenous shrinkage. This effect may be due to the hydration and the self-desiccation processes which are accelerated at high temperatures.

Strain-hardening Ultra-high Performance Fibre Reinforced Concrete: Deformability versus Strength Optimization

High Performance Cement-based composites such as some UHPFRC or SHCC exhibit a tensile strain hardening response associated to the progressive formation of finely distributed microcracks. Strain Hardening (SH) - UHPFRC with suitable fibrous mixes have a dense matrix, a very low capillary absorption of liquids, significant viscoelastic potential and limited shrinkage. They exhibit a tensile strain hardening response up to 0.3 ‰. Strain hardening materials are candidates for improving existing or new structures to increase their durability and mechanical performance. With this aim in view, the impact of macro and microcracking on the protective function and corrosion mechanisms in cementitious materials has to be critically weighed to choose adequate materials in terms of strength and deformability, to fulfil durability requirements. From this basis, the mechanical response (strength, deformability and associated crack formation) can be tailored according to the applications. Finally, future steps for the development and applications of these advanced contemporary materials can be defined.

Visualization of in-plane displacement fields by using phase-shifting holographic moiré: application to crack detection and propagation

Phase-shifted holographic moire is shown to provide highly improved visualization of the phase fields corresponding to in-plane displacements. Outstanding capabilities in the study of crack process are demonstrated.

TAILORED COMPOSITE UHPFRC-CONCRETE STRUCTURES

Note: Springer Verlag Reference MCS-CONF-2007-006View record in Web of Science Record created on 2007-04-20, modified on 2016-08-08

CHLORIDE PENETRATION MODEL CONSIDERING MICROCLIMATE

Two main factors govern the ingress of chloride ions into concrete reinforced with ordinary steel reinforcement, from de-icing salts: (1) the cover concrete (permeability, thickness), and (2) the microclimatic conditions (humidity, temperature, concentration of de-icing salts) at the concrete surface. A numerical model of chloride transport, taking into consideration environmental conditions (temperature, humidity, snow, rain and salt spreading), was used to predict the chloride profiles in concrete representative of that found in bridge element, for two types of exposure to water (splash, mist). This model was applied for two different regions in Switzerland: on the plateau in Lausanne, where there is a relatively mild winter climate and in the Alps where there is severe winter climate.

Moisture Diffusivity of Fiber Reinforced Silica Fume Mortars

The moisture diffusivity is of considerable importance for quantitative assessments of creep and shrinkage as well as durability of cementitious material. For this reason, the influence of the composition of repair mortars on their effective moisture diffusivity as a function of the relative humidity of the surrounding air has been investigated. Silica fume,

Effect of fiber orientation and specimen thickness on the tensile response of strain hardening UHPFRC mixes with reduced Embodied Energy

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.

Experimental study of tensile response of Strain Hardening UHPFRC at early age

Strain Hardening Ultra High Performance Fibre Reinforced Concrete (SH-UHPFRC), has a high tensile strength (over 10 MPa) and exhibit significant strain hardening (several ‰) under tensile loads. These appealing features make it a suitable material for improving the efficiency and durability of new or existing structures. However, in rehabilitation works, when a layer of a new material is applied on an existing structure, due to restraints from the existing structure, the shrinkage deformations lead to high tensile stresses in the new layer, which can lead to premature cracking.