Analysis of long-term corrosion behavior in mortars containing recycled ladle furnace slag using computerized tomography and SEM

A series of mortars subjected to accelerated corrosion in a humid environment form the basis for this study. In particular, we studied the corrosion behavior of steel reinforcement bars that were embedded in cement mortars that contained white ladle furnace slag (LFS) in partial substitution for fines and cement. The effects were observed using computerized axial tomography and scanning electron microscopy. Zones with fissures resulting from corrosion and the degree of damage due to passivation were identified from the imaging analysis

Reutilisation of hazardous spent fluorescent lamps glass waste as supplementary cementitious material

[EN] Spent fluorescent lamps glass (SFLG) waste, manually and mechanically processed in a lamps waste treatment plant, was used to partially replace up to 50 wt% Portland cement (PC). Both waste types exhibited similar pozzolanic activity. The mortars containing up to 35 wt% SFLG met the specifications for other pozzolanic materials (e.g. fly ash) and, after 90 curing days, their compressive strength values were sim- ilar to or higher than those of the 100% PC sample (58.8 MPa). Our results provide an alternative reutilization process for this hazardous waste to reuse SFLG as-received (no washing to reduce mercury) and contributes to less PC useThis work was supported by the Universitat Jaume I of Castellon [Project UJI-B2019-21], and the Spanish Ministry of Education, Culture and Sport [research collaboration grant, academic year 2015/2016].Pitarch, A.; Reig, L.; Gallardo, A.; Soriano Martinez, L.; Borrachero Rosado, MV.; Rochina, S. (2021). Reutilisation of hazardous spent fluorescent lamps glass waste as supplementary cementitious material. Construction and Building Materials. 292:1-13. https://doi.org/10.1016/j.conbuildmat.2021.123424S11329

Etude de l\u27endommagement et du renforcement de composites à matrice cimentaire

Ce travail de thèse s\u27inscrit dans le cadre général des études sur l\u27élaboration et la caractérisation des composites à matrice cimentaire. Dans notre cas, nous avons choisi le béton comme composite à matrice cimentaire, ce dernier résulte du mélange de plusieurs éléments : ciment, eau, granulats, adjuvants et fibres. Mon travail se propose de mieux comprendre d\u27une part l\u27influence des rapports sable sur ciment (s/c) et eau sur ciment (e/c) sur la microstructure, les mécanismes de l\u27endommagement et le renforcement et d\u27autre part le rôle de l\u27interface pâte-granulat dans ce mélange. Pour atteindre ces objectifs, dans un premier temps des essais de traction et compression ont été effectués avec un suivi de l\u27activité acoustique. De plus, des analyses en tomographie X ont été réalisées afin d\u27identifier les mécanismes d\u27endommagement. Dans un deuxième temps des observations microscopiques ont été menées afin d\u27examiner les changements microstructuraux. Des mesures de porosités ainsi que des analyses thermogravimétriques ont été effectuées. Deux systèmes ont été conçus pour réaliser les tests mécaniques. Le premier est un système de traction direct, adapté aux conditions de l\u27étude, qui a été mis au point au cours de ce travail. Ce système consiste en plusieurs articulations pour faciliter l\u27alignement de l\u27éprouvette lors de l\u27essai. Un second système pour effectuer les essais en compression a été réalisé. Pour ce dernier nous avons utilisé une calotte sphérique afin d\u27optimiser les défauts de parallélisme de deux surfaces de l\u27éprouvette

Valorization of Recycled Aggregate in Concrete and Mortar

In this study, the influences of partial replacements of sand by fine recycled aggregate (RA), and replacement of cement by very fine RA, on the mechanical behaviour and the microstructure changes of mortar were investigated. An experimental program was carried out for producing mortar incorporated with large volumes of RA of various particle sizes. Using the two-step method, five mixtures were made for each part of study (part 1: only aggregate less than 630µm, and part 2: 360µm were replaced by natural aggregate NA), starting by a mix with 100 % of RA, and then 75%, 50%, 25% and 0%. Prism samples were molded in (4*4*16 cm) for mechanical testing (flexure and compression). The results obtained showed that it is possible to use the fine RA to give mixes with compressive strength and flexure strength close to the control mix. Moreover, the use of super-plasticizer leads to a significant increase for both strengths. In the case of the replacement of cement with the very fine RA and in order to obtain green cement, both compressive and flexure strengths are closer to the control mix, which is consistent with microstructure investigations

Etude de l'endommagement et du renforcement de composites à matrice cimentaire

Ce travail de thèse s'inscrit dans le cadre général des études sur l'élaboration et la caractérisation des composites à matrice cimentaire. Dans notre cas, nous avons choisi le béton comme composite à matrice cimentaire, ce dernier résulte du mélange de plusieurs éléments : ciment, eau, granulats, adjuvants et fibres. Mon travail se propose de mieux comprendre d'une part l'influence des rapports sable sur ciment (s/c) et eau sur ciment (e/c) sur la microstructure, les mécanismes de l'endommagement et le renforcement et d'autre part le rôle de l'interface pâte-granulat dans ce mélange. Pour atteindre ces objectifs, dans un premier temps des essais de traction et compression ont été effectués avec un suivi de l'activité acoustique. De plus, des analyses en tomographie X ont été réalisées afin d'identifier les mécanismes d'endommagement. Dans un deuxième temps des observations microscopiques ont été menées afin d'examiner les changements microstructuraux. Des mesures de porosités ainsi que des analyses thermogravimétriques ont été effectuées. Deux systèmes ont été conçus pour réaliser les tests mécaniques. Le premier est un système de traction direct, adapté aux conditions de l'étude, qui a été mis au point au cours de ce travail. Ce système consiste en plusieurs articulations pour faciliter l'alignement de l'éprouvette lors de l'essai. Un second système pour effectuer les essais en compression a été réalisé. Pour ce dernier nous avons utilisé une calotte sphérique afin d'optimiser les défauts de parallélisme de deux surfaces de l'éprouvette.This PhD work comes within the scope of the study of the elaboration and characterisation of cement-based materials. In our case, we have chosen concrete as cement-based material. Concrete is the result of mixing cement, water, aggregate, adjuvant and fibres. I have tried to understand on the one hand, the influence of the sand to cement ratio and of the water to cement ratio on the microstructure and damage mechanisms, and on the other hand, the role of the interface aggregate-cement paste in the mixture. To achieve this, we have first done tensile and compression tests, while monitoring the acoustic emission and the tomography X, in order to identify the damage and reinforcement mechanisms. We have then done microscopic observations so as to examine the microstructure changes. We have also measured the porosity and done thermogravimetric analyses. Two systems were developed for these mechanical tests. One is a direct traction system, fitted to the conditions of the study and it was designed during this work. It consists of several articulations to facilitate the alignment of the specimen during the testing. The second system allows carrying out compression tests. We have used the segment of a sphere in order to optimise the parallelism defects of two surfaces of the specimen.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

Analysis of Damage of Reinforced Mortar by Non-Destructive Methods

The aim of this study is the improvement of the potential of coupling between non-destructive methods on damage characterization of mortar (acoustic emission and ultrasound). The mortar is a very heterogynous material, in which damage can be estimated by the method of the ultrasounds. It is also fragile, which allows to have intense signals by the technique of acoustic emission. The results obtained on this paper concern the reinforced mortar by steel fibres, show that damage can be describe in three stages of damage. Stage 1, where there is no acoustic activities, stage 2, correspond the increase of the attenuation according to the increase of the value of the applied strength. This value depends very strongly on the applied strength, then the strength is strong, the attenuation is important. The value of the attenuation in the case without load is very different from that observed just before the failure in third stage

Damage evolution analysis in mortar, during compressive loading using acoustic emission and X-ray tomography: Effects of the sand/cement ratio

International audienceThis paper explores the use of acoustic emission (AE) and X-ray tomography to identify the mechanisms of damage and the fracture process during compressive loading on concrete specimens. Three-dimensional (3D) X-ray tomography image analysis was used to observe defects of virgin mortar specimen under different compressive loads. Cumulative AE events were used to evaluate damage process in real time according to the sand/cement ratio. This work shows that AE and X-ray tomography are complementary nondestructive methods to measure, characterise and locate damage sites in mortar. The effect of the sand proportion on damage and fracture behaviour is studied, in relation with the microstructure of the material

تأثير طريقة خلط بودرة الزجاج كبديل للاسمنت على الخواص الميكانيكية للخرسانة

This study investigates the effects of using local wastes of Glass Powder (produced from crushing the glass waste) as replacement of cement in fresh and hardened concrete. Four percentages of Glass Powder (GP) were used: 0%, 10%, 20%, and 30%. Two mixing methods were used in the study. First, the conventional mixing method, where the glass powder was added with the cement and aggregates. Second, the glass powder was dissolved in water before adding it to cement and aggregates. The slump increased as the glass powder replacement increased in the concrete due to the presence of more free water in the structure, which leaded to have lower density and higher water absorption. As a result, the compressive strength of conventional mixes method decreased as the glass powder increased at early age. Later, after 90 days, the highest compressive strength was obtained for the 20% GP. The new mixing method showed higher compressive strength than the conventional mixing method. Using 10% GP in the new mixing method gave a significant increase, around 130% of the compressive strength of the control mix. This increase can be related to the hydrolysis of the glass powder into free ions of SiO2, CaO and Na2O in the water which formed more CSH. The relative index proves the rise of the glass powder reactivity as the amount of glass powder increases.لا يوج

Hysteretic elasticity in damaged concrete: quantitative analysis of slow and fast dynamics

International audienceFast and slow dynamics in the elastic response of damaged materials to external excitations show evidence of an anomalous (hysteretic) elastic behavior. Experimental observations may be used to detect and eventually characterize the damaged state of structural components. At the same time, reliable theoretical models might support data interpretation and development of new experiments. Here, we analyze the resonance frequency shift in undamaged and damaged concrete bars, comparing experimental results and theoretical predictions obtained from a Preisach-Mayergoyz based elastic mode