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The Alfa plant is indigenous and spans a large zone throughout North Africa. Recently, Alfa plant has been used in building materials, notably as a reinforcement. This study aims to valorize the Alfa plant into fiber-reinforced mortar based on a cement-glass composite mix design. Two Alfa fiber morphologies are considered herein: different cutting lengths (10, 20 and 30 mm), and ground using a knife mill (shorter than 2 mm). These fibers were added to mortars at various volume ratios: 1, 2 and 3%. The workability and density of these distinct formulations were then measured in their fresh state. In comparison with the control mortar (CM), the introduction of Alfa fibers (either cut or ground), with ratios below 2% vol., leads to a slight decrease in mixture workability. However, Alfa fibers do not significantly alter the fresh material density. It was recorded a delay in setting time of the composites as a function of fiber addition rate. In the hardened state, an improvement in flexural strength is noticed for mortars reinforced with 1% vol. of fibers compared to the CM. However, results show that the increase in either type of fiber (cut or ground) generates a decrease in compressive strength compared to the CM. This outcome can be confirmed by both the decrease in heat released during the hydration reaction and water-accessible porosity inside the matrix.

To ensure a performing demoulding, a release agent must resist the friction of concrete on the formwork. Emulsions are interesting alternatives that leads to a reduced consumption of oil on construction sites. The behaviours of two commercial emulsions are compared with two conventional demoulding oils. The adhesion energy calculated were favourable to the emulsions. The water evaporation kinetics leads to the measurements of film thickness. Tests with the tribometer have shown that the films produced from the emulsions generate a friction reduction of 30% and 40% at the concrete/formwork interface. Such performance can be explained by Wenzel's state of wettability, which facilitates the film fit into the formwork roughness.

A reduction in rehabilitation costs by about 20% is the main objective of this project while reducing response times in situ and maintaining an equivalent efficiency of the reinforcement. The first part recounts the history of the various stages of the Parisian sewer system construction. It subsequently takes stock of the pathologies, the repair techniques and the investigation methods of these structures. The second part deals with the design of test pieces through numerical calculation while taking into consideration the various parameters applied to each material. The selected model is a vault representing the upper part of an ovoid. The third part is an experimental approach to characterizing materials and in particular the coating/glue/composite interface.

International audience; The quality of the concrete facings results from the implementation of release agents and the casing surface quality. It is interesting to characterize the behaviour of release agents over the lifetime of the formwork. This study is based on the many ones test physicochemical and esthetics realized on two types of surface of formwork like on three types of applications. In complement, the ageing of the casing formwork was characterized by electrochemical spectroscopy of impedance and thanks to the correlation with the aesthetic tests will allow to find from new mechanisms to the interfaces related to the studied oil's formulations. (C) 2014 Elsevier Ltd. All rights reserved.

A recent study proposed a new process for demoulding concrete elements based on the principle of electro-osmosis, consisting of applying an electric potential between the reinforcement and formwork which causes the water displacement towards the concrete/formwork interface where a film of water is formed avoiding the adhesion of the concrete on the formwork. The quality of facing and demoulding has been shown to be dependent on the polarization parameters (voltage value, time and duration of its application) and therefore optimal parameters were assessed. However these parameters were found in a very limited condition of temperature, only at 20 ± 2 °C. In this new study we consider the parameters optimization scheme in other room temperature conditions. In this respect an experimental device was developed in order to quantify the amount of displaced water at (20 ± 2 °C) and (8 ± 2 °C) according to the voltage value and duration of its application. We showed that, under the same polarization conditions, the quantity of water transported decreases with decreasing room temperature. This decreasing of water quantity caused the alteration of demoulding and facing quality. To overcome this issue, the optimal polarization conditions have been revisited in order to take into account the temperature. When transposed in situ, our method performed successfully at 20 ± 2 °C and at 8 ± 2 °C as well and it could be a better choice than the previous demoulding methods like those using vegetable oils, developed recently to replace mineral oils, they cannot be used at low temperatures.

Sewerage systems undergo a wide variety of structural damage. It is estimated that 10% of French sewer length is in need of renovation. This paper is concerned with restructuring by carbon-fibre plates. The finite-element method is necessary to obtain the failure mechanism and thus locate the areas in need of strengthening. Experimental tests were conducted to characterise the materials (concrete, adhesive and carbon-fibre plates) and then obtain their constitutive laws. A control ovoid and a carbon plate-strengthened ovoid were compared.