Hamza Soualhi

1. Owing to the economy’s rapid growth and the rising demand for real estate, many cities now face the challenge of rebuilding old sites, which generates large amounts of construction and demolitio...

Il est possible de modifier la composition des bétons utilisés dans le domaine de la construction pour réduire sensiblement le dégagement de CO2 associé à leur fabrication. Ceci est obtenu en réduisant significativement la quantité de clinker et en incorporant des matériaux de substitution appelés additions. Elles sont généralement moins réactives et demandent, pour maintenir un niveau acceptable de performances mécaniques et de durabilité, une réduction importante du dosage en eau. C'est le cas des bétons à faible impact environnemental. L'utilisation de superplastifiant dans ces bétons permet d'augmenter leur fluidité mais leur viscosité plastique reste toujours élevée ce qui induit des problèmes de mise en œuvre. La maîtrise de la viscosité plastique de ce type de béton est donc cruciale pour le développement de ces produits.Avec cet objectif fixé, dans la première partie de cette étude, un rhéomètre à béton, adapté aux spécificités des bétons à faible impact environnemental, a été développé. Associé à un protocole d'essai pertinent cet appareil permet de caractériser le comportement rhéologique non seulement des bétons courants mais également des bétons à faible impact environnemental.Ensuite, l'utilisation de ce rhéomètre dans un programme expérimental a permis de mettre en évidence l'effet des paramètres de compositions et notamment le taux de substitution et la nature des additions sur leur comportement rhéologique.Les résultats obtenus à partir de ce programme ont permis de proposer et valider un modèle de calcul de la viscosité plastique en considérant que le béton est constitué de deux échelles : pâte et granulats. Le modèle est applicable pour les bétons ordinaires et pour les bétons à faible impact environnemental. Une méthode d'optimisation de la viscosité a été proposée à l'aide du modèle.

Clarifying the contrasting effects of limestone fillers in cement-based materials is crucial for the sustainable valorisation of quarry by-products. This study investigates the influence of three limestone fillers – quarry limestone dust (2985 cm²/g), commercial limestone filler (4690 cm²/g), and laboratory-ground limestone powder (4073 cm²/g) – on the rheological and mechanical properties of cement mortar. Two substitution strategies were considered: replacing sand (0–20%) with quarry limestone dust and laboratory-ground powder, and replacing cement (0–30%) with commercial filler. Quarry dust substitution reduces workability with little effect on strength, but washing and superplasticiser restore consistency. In contrast, cement replacement with commercial filler improves workability but decreases strength. Laboratory-ground limestone powder from washed sand, with finer particles and higher purity confirmed by XRD and FTIR, exhibited a nucleation effect and increased strength by 32.7% at 7 days. These results demonstrate that the impact of limestone fillers is governed by their origin, fineness, and substitution route, offering insights for optimising mortar formulation and enabling efficient utilisation of quarry by-products without compromising performance.

Aggregates recycled from construction sites may exhibit slightly inferior characteristics compared to natural aggregates in terms of porosity, friability, and variability. However, it must be acknowledged that although recycled aggregates are currently used only in small proportions for manufacturing concrete, their usage is steadily increasing. It is now widely recognised that the reuse of recycled aggregates in mortar and concrete significantly contributes to the preservation of alluvial aggregates. The valorisation of recycled aggregates in concrete and mortar offers a clear economic advantage in the construction sector. Indeed, the reuse of materials from demolition could be envisaged directly on site or at construction waste recycling and treatment platforms. Additionally, it should be noted that to date, there is no specific standard for measuring the water absorption of recycled aggregates. Regarding the physical properties, the estimation of the absorption kinetics of the recycled aggregates has proved necessary. Moreover, other equally important measurements must be undertaken to determine all the other properties. The results obtained demonstrated that a good correlation exists between the substitution rate and the physical and mechanical properties of the prepared concrete. Furthermore, it was decided to vary the substitution rate of natural sand with recycled sand during the manufacture of concrete according to the following percentages: 25% recycled sand with 75% natural sand, and 50% recycled sand with 50% natural sand.

– Mortar is a mixture of sand, cement, water and eventually additives. With the environmental issues, mortars are increasingly formulated with mineral additions as a substitute for cement in order to produce ecological mortars. It is one of the most widely used cementitious materials in the field of construction and civil engineering after concrete. Mortar placement techniques are evolving day by day, such as pumping, spraying and injection. Therefore, knowing the rheological behavior of mortars becomes more and more crucial to master their implementation techniques. This study presents the development of a vane rheometer to estimate the plastic viscosity yield stress of mortars. The rheological parameters were developed from measurements using a procedure to convert data from moment torque and rotational speed to shear stresses versus shear rate. The procedure used considered the locally sheared material as a Bingham fluid and calculated the characteristic shear rate from the quilt analogy. The device was tested with three experimental programs in which many rheological parameters of the compositions of different mortars were calculated. The results obtained validated the developed rheometer test procedure and confirmed that the test results are reproducible and repeatable. Measurements were made on different compositions of mortar of each mineral addition, altering the amount of blast furnace slag (BFS) and fly ash (FA) in order to evaluate the impact of supplemental cementitious materials and industrial wastes on the rheological characteristics (plastic viscosity and yield stress) of eco-friendly mortar..

It is widely recognized that today people around the world still admire the Egyptian civilization and wonder how Egyptians came to manufacture mortar. The present work aims to study the construction materials that were used in ancient Egypt and their development over time. To do this, it was decided to first evaluate the physical and mechanical performances of the building materials used at that time and then try to investigate and understand the handling process as well as the construction methods adopted currently. For this, cement (NA442 CEM II/B-L 42.5 N) and local sand were replaced at different proportions with lime in the formulation of mortar, the sand used whose mixture was relative to that of the sand (0/4) and (0/1) values of 65% and 35%, respectively. A number of tests were carried out on two types of mortar prepared with two different formulations. The first formulation, which included quicklime, was subjected to a simple treatment in order to obtain aerial lime and to understand the different formulation stages that were followed in the Ancient Egyptian times. Knowing that the objective was to revive the method of manufacturing works from the ancient era, thus using a variable rate of substitution (0%, 50% to 70%) of lime, limestone and gypsum to obtain the binder by also studying the stakes of this variation on the reduction of the quantity of cement in the mortar which consisted in the preparation of fourteen test series in order to converge on the impact of the experiments sought. The second one consisted, at a later time, in preparing some series of mortar incorporating aerial lime brought from the manufacturing plant. After analyzing the prepared material, it was deemed interesting to attempt to quantitatively reconstruct the composition of the material using the Vicat test for the purpose of assessing the cement slurry setting process for stylolithic joints which, to the best of our knowledge, are very well developed only in limestones. Also noting that, the composition of the mortar and the rate of substitution evolved according to the results obtained upstream while keeping the objective of this research which was to reproduce a composition compatible with the old days.