Browsing by Author "Oualit, M."

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Effect of Black Liquor from Date Palm on the Workability and Compressive Strength of Portland Cement and Concrete
(De Gruyter Open Sp. z o.o., 2019) Irekti, Amar; Oualit, M.; Siahmed, H.; Buncianu, D.; Zibouche, Fatima
Lignin is the second most abundant natural polymer. Due to the high content of carbon and hydrogen (C-H, C-C, C=O), it can be used as a potential dispersant for cement matrix. The objective of this study is to extract lignin from date palm and study its effect in the form of black liquor (BL) on the rheological and physic-mechanical properties of the cements and concrete. The lignin in black liquor form represents approximately 30 wt% dry weight of date palm. It is a heteropolymer composed primarily of methoxylated phenylpropylene alcohol monomeric units interconnected by a variety of stable carbon-carbon and carbon-oxygen-carbon (ether and esters) linkages. The results found show the positive effect on the workability of cement and concrete and confirms its dispersion effect by improving compressive strength of concrete during the early and the later ages of hydration.
External corrosion to concrete sewers : a case study
(2012) Oualit, M.; Jauberthie, R.; Rendell, F.; Melinge, Y.; Abadlia, Mohamed Tahar
The aim of this study was to investigate the deterioration of concrete sewers and identify responsible factors; this investigation was a part of an ongoing asset evaluation for Rennes (France). The sewer studied was a 300 mm spun concrete pipe laid in 1992. Core samples (D 28 mm, L 40 mm) were taken from different areas of a pipe (invert, crown and side wall) and analysed to quantify the condition of the concrete and the extent of damage to the internal and external surface of the pipe. Physical and mechanical properties of the material were characterised. The depassivation of the concrete was measured by testing with a phenolphthalein solution. The study showed that in this particular case the external corrosion was extensive with minimal internal corrosion. It is proposed that the corrosion was possibly linked to the use of a contaminated backfill or organic acids in the ground water. Recommendations are proposed concerning the direction of future research
Pérennisation des ouvrages en génie civil : diagnos tic et inspection des bétons d’egouts
(2012) Oualit, M.; Abadlia, Mohamed Tahar; Hami, B.
La durabilité des bétons dans les réseaux d'assaini ssement est principalement affectée par l’action combinée, chimique (sels, sulfates, acides...), mécaniques (poinçonnement, abrasion...) et biologiques (bactéries aérobies, anaérobies...) provoquant une détérioration souvent de la matrice cimentaire. Ces dégradations sont souvent aggravées en fonction de la vitesse, la nature, la concentration et le pH ai nsique les conditions environnementales aux alentours (taux d’oxygène, empérature...etc). L’objectif de ce travail qui a été réalisé à l’INSA de Rennes consiste à effectuer une étude sur la dégradation et les facteurs responsables d’altération du béton employé dans le réseau d’égouts de la ville de Rennes. Ainsi, des échantillons prélevés dans différentes zones (radier, medium et toit) d’une conduite ont été analysés à l’aide de moyens d’investigation afin de mettre en évidence l’état d’endommagement interne due aux effluents et externe (sol) de résea u ainsi que les modifications chimiques et minéralogiques enregistrées. Ces essais sont complé tés par une caractérisation physique et mécanique. Dans cet article, nous présentons les résultats de l’inspection d’un tronçon dont les sollicitations prédominantes sont en majorité chimiques et abrasiv es. Cette étude met clairement en évidence la très fort e anisotropie des dégradations aussi bien internes qu’externes. Enfin, des ecommandations seront proposées en adéquation avec l’environnement ainsi qu’une évaluation de la perte de performance des conduits
Performance and analysis of concrete in sewer environment : anisotropy of damage
(2011) Oualit, M.; Jauberthie, R.; Melinge, Y.; Abadlia, Mohamed Tahar
The costs associated with the provision and maintenance of drinking water and wastewater infrastructure represents a signiﬁcant ﬁnancial demand worldwide. Maintenance costs are disproportionately high, indicating a lack of adequate durability. The aim of this paper is to study the degradation mode and the responsible factors of deterioration concrete pipe, used in the sewage’s city of Rennes (France). Thus, samples taken from different areas of the pipe (Raft, medium and roof) were analyzed using investigation methods in order to illustrate the internal and external rate of damage, caused by effluents and ground. In addition, chemical and mineralogical changes recorded were identified using scanning electron micrographs (SEM). In this research program, chemical and mechanical studies were performed by measuring the compressive and splitting tensile strengths. A phenolphthalein indicator solution is applied to a concrete specimen on a fresh fracture surface to determine the corrosion of steel reinforcement and the diseases advancement (pathologies depth). This study clearly shows the important anisotropy of both, internal and external damage. Finally, recommendations are proposed in line with the environment and possible approaches to sustainability assessment are also imposed