Malek Jedidi

In this work, plaster and natural Posidonia Oceanica (PO) fibers are combined to create a composite material that was recently produced. This work’s primary objective is to assess the mechanical and thermophysical performance of the composite material in order to determine whether or not it may be used as a thermal and acoustic insulation material in buildings. For this end, prismatic and parallelepipedic specimens of different dimensions were made with fiber percentages ranging from 0% to 20%. In addition, parallelepiped panels (600 mm × 600 mm × 40 mm³) were also prepared containing 10% of PO fibers. Mechanical properties (flexual strength, compressive strength), thermal properties and sound absorption coefficient were investigated. For each test specimen, the density was calculated for a proportion of fibers ranging from 0% to 20%. The results indicated a marked improvement in the compressive and flexural strength of the fiber-reinforced mixtures. This improvement is respectively 14.5% and 33.8% for mixtures containing 10% of PO fibers. Additionally, the addition of PO fibers significantly decreases density (by 40.5%), thermal conductivity (by 68.5%) and thermal diffusivity (by 36.9%) of the different mixtures. The ideal mechanical characteristics are attained when 5%–10% of the volume is made up of Posidonia Oceanica fibers. The results of the sound absorption coefficient test show that the mixture of plaster with 10% fibers has a good sound absorption coefficient of 0.78 for high frequencies between 1000 Hz and 4000 Hz. This work has shown conclusively that the incorporation of PO fibers, up to a maximum of 10% with plaster, makes it possible to obtain a lightweight composite that can potentially be used as a new insulating construction material.

In the past few years, several concrete constructions have suffered major fires, causing very significant damage to the structure. The fire resistance of concrete depends on some of its characteristics such as the nature of the components used for its formulation, permeability, water content and mechanical resistance. In the places most exposed to fire, all the coating can be expelled, which seriously threatens the bearing capacity of the construction. In addition, the financial loss due to repair over a long period can reach several million Euros. This paper presents the physical and chemical transformations caused by the increase in the temperature of concrete in the event of a fire. These transformations mainly have an effect on the microstructure, the mechanical properties and the thermal deformation of concrete. The two phenomena of flaking and spalling of concrete were also studied in order to know their origins and found the methods of preventive. Indeed, flaking can manifest itself explosively, and have significant consequences on the resistance of concrete. It thus reduces the cross-section of the structure and also decreases its bearing capacity, which leads to an increase in the risk of structural failure. The factors influencing the flaking phenomenon were also presented.

Concrete is a material whose properties depend on its initial formulation, its conditions of use, and its change over time depending on its environment and the different types of degradation that it is likely to undergo. Knowledge and monitoring of its various mechanical properties are therefore essential for the maintenance of civil engineering works. All of the concrete assessment methods, whether destructive or non-destructive, can then provide a valuable diagnosis to the operators of the structure. Depending on their precision, they can be used to easily detect an alteration in the characteristics of the materials, locate a damaged area, the extent of the damage, or even precisely quantify the evolution of this damage over time and predict future changes. This paper presents the Ultrasonic Pulse Velocity technique (UPV) which is used by many companies to assess the compressive strength of concrete in situ and which allows measuring the speed and attenuation of elastic waves. The influence of the reinforcements on the ultrasonic pulse velocity has been studied and this is in the case of reinforcement perpendicular and parallel to the direction of propagation. The influence of several factors affecting the UPV, whether related to the properties of concrete or otherwise, was mentioned. Indeed, the porosity, the water/Cement ratio, the micro-cracks, the state of saturation and the temperature of concrete are parameters which strongly influence the values of UPV.

The present work focused on the experimental study of the mechanical, thermal and acoustic properties of cement composite reinforced using Posidonia oceanica (PO) fibers. For this purpose, parallelepipedic specimens of dimensions 270 mm × 270 mm × 40 mm and cubic specimens of dimensions 150 mm × 150 mm × 150 mm were prepared with a water-to-cement ratio of 0.50 by varying the volume of fibers (V_f) from 0% to 20%. Properties such as compressive strength, thermal conductivity, thermal diffusivity, standardized level difference and sound transmission class were examined. The compressive strength of the specimens was determined using the rebound hammer test, while the thermal measurements were performed with the steady-state box method. The results showed that the addition of PO fibers improved the compressive strength of the mixtures and produced a maximum value of 33.60 MPa for a 10% volume of fiber content. Thermal conductivity and thermal diffusivity decreased significantly with the addition of fibers for all the mixtures. The experimental investigation also showed that the sound transmission class of PO-fiber-reinforced cementitious composites decreased as the fiber volume increased due to an increase in air voids in the mixtures.

In recent years, the durability of concrete has been the subject of a few research projects carried out by several scientific and technical centres. As a major cause of concrete degradation around the world, reinforcing steel corrosion requires our full attention. This article analyses one of the phenomena at the origin of these disorders, namely the carbonation of concrete, and proposes some provisions to guard against it. The article is divided into two parts; the first describes the causes and consequences of the chemical process of carbonation as well as the means to protect it. The second deals with the influence factors on carbonation such as the minimum cement dosage, the type of cement, the water-cement ratio (W/C) and the reinforcement coating. Indeed, prismatic specimens (15 x 15 x 60 cm3) and cubic specimens (15 x 15 x 15 cm3) were made for different mixtures and with a W/C ratio of 0.50, 0.55 and 0.60. The prismatic specimens were subjected to a carbonation test, while the cubic specimens were used to determine the compressive strength, the corresponding density and the immersion water absorption.

The purpose of the present study is to recover marble waste and expanded perlite aggregate (EPA) for use as an additive to cementitious matrix building materials. The main goal is to produce a new insulation block floor from lightweight concrete (LC) by mixing sand from the waste marble crushing process (SWM), natural sand, and EPA. First, optimal mixture of natural sand, SWM, and EPA was determined for a given insulation LC. To this end, plate and cubic specimens were prepared by varying the volume proportion of SWM to natural sand in percentages of 0, 20, 40, 60, 80, and 100. Mechanical and physical properties such as the compressive strength, thermal conductivity, thermal diffusivity, specific heat capacity, and sound reduction index at different frequencies were investigated. Finally, a prototype of a new insulation lightweight block floor was manufactured from the optimal mixture of the studied LC. The results showed that the incorporation of SWM significantly improved the mechanical properties and the thermal insulation of LC compared to those of the natural sand. These results are promising and give the present insulation block floor the opportunity to be used in composite slabs.

Thermal bridges in the thermal insulation of envelopes occur in all forms of building construction and should be minimised to reduce local heat losses. This paper presents the effect of thermal bridges on the comfort of the habitat within a building. Indeed, the thermal bridges increase the heat losses of a building and thus the consumption of heating. Thermal bridges cause additional heat losses compared to losses through the walls of the building. These losses can exceed for some 40% of the total heat losses through the envelope. An example of an energetic effect of a thermal bridge has been presented. For this example, the heat losses on a floor height and per meter of facade were calculated. The results showed that from 5 cm thickness of insulation, the difference between the loss curve in the absence of thermal bridge, and the loss curve taking into account the thermal bridge is almost independent of the thickness of the insulating. Another example was also presented to demonstrate the effect on thermal bridging when increasing the levels of insulation to a normal corner. The results showed that for a 50% and 100% increase in the thickness of the insulation, the U-value, linear heat loss coefficient ? and surface temperature factor fRsi were considerably decreased.

Current research in the field of building materials is oriented towards the recovery of waste to ensure the lightening of certain building elements and energy saving. The objective of this study is to produce a new bricks by adding sawdust to clay mixtures. The first part of this experimental work consists on detremining the proper manufacturing process and cooking diagram for these new bricks. In the second part, the effect of the maximum cooking temperature, the firing phase time's of the bricks and the sawdust prportion on the physical and mechanical properties of the new bricks have been studied. The studied properties are the absorption ratio, the unit weight and the compressive strength. The results showed that the addition of an increasing amount of sawdust tends to modify the physical and mechanical properties of the cooked samples. The presence of sawdust reduces the number of connections between the clay grains and produces a lighter, more absorbent and less resistant material. Finally, the results showed that the manufacture of bricks based on sawdust is possible. La recherche actuelle dans le domaine des matériaux de construction est orientée vers la valorisation des déchets pour assurer l’allégement de certains éléments de construction et une économie d’énergie. L'objectif de cette étude est de produire des nouvelles briques d'argile plus légères que celles qui sont actuellement sur le marché, en ajoutant des sciures de bois aux mélanges d'argile. Plusieurs paramètres ont été étudiés ainsi que leur effet sur les modifications des propriétés physiques et mécaniques tels que le taux d’absorption, la température maximale de cuisson, la proportion des sciures et la durée de la phase de cuisson de ces briques. Un processus de fabrication, de séchage et de cuisson a été adapté au nouveau produit. Les résultats ont montré que l'addition d'une quantité croissante de sciures tend à modifier sensiblement les propriétés physiques et mécaniques des échantillons cuits. La présence de sciures réduit le nombre de connections entre les grains d'argile et produit un matériau plus léger, plus absorbant et moins résistant. Enfin, les résultats ont montré aussi que la confection des briques à base des sciures de bois est possible.