Zoubeir Lafhaj

Experimental study of gas and liquid permeability of a mortar

Eight samples cored from the same mortar were used to investigate their respective gas, ethanol and water permeability. Two gas and liquid permeability cells, using special devices for measuring the injected flow under steady conditions, were designed and presented in this paper. The obtained results showed that water permeability was systematically lower (in an order of magnitude from 1 to 2) than gas permeability whereas ethanol permeability was intermediate between these two values. Nevertheless, ethanol and gas permeabilities were found of the same order and, when gas permeability is corrected from the Klinkenberg (or slippage) effect, the results given by these two fluids are virtually identical and can be considered to be the intrinsic permeability value. Thus, the differences observed between water and gas permeability values have to be explained by other phenomena such as rehydration, dissolution and migration of fine elements or water adsorption in the thinnest pores.

Valorization of stabilized river sediments in fired clay bricks: Factory scale experiment

The objective of this study is to demonstrate the practical use of polluted river sediments after treatment into brick production. Consequently, a full-scale industrial experiment was conducted at a brick factory in the north of France. Polluted sediment was stabilized by the Novosol process and then was introduced in the mix-design with a substitution ratio of 15% as a partial replacement of quartz sand. Approximately 15,000 perforated sediment-amended bricks were produced. The produced bricks were then subjected to several qualification tests (compressive strength, freeze and thaw resistance, water absorption). The results obtained showed that the substitution of quartz sand by treated sediment resulted in a significant increase in brick compressive strength and firing shrinkage, and in a decrease in porosity and water absorption. Moreover, leaching tests performed according to different standards on substituted brick samples showed that the quantities of heavy metals leached from crushed bricks were within the regulatory limits. Thus substituted bricks can be regarded as non-hazardous material.

Introducing a multi-criteria indicator to better evaluate impacts of rare earth materials production and consumption in life cycle assessment

Life cycle assessment (LCA) is based on the basic principles of sustainable development. LCA method demonstrated its efficiency in providing a systematic environmental assessment approach of a product or a process. The effectiveness and efficiency of these methods lies in the fact that they take into account all life cycle stages of a product, from the extraction of raw materials to end of life treatment (recycling, ...) through an assessment covering different impact categories such as climate change, human health, ecosystems and resources. Existing LCA indicators reflect different issues surrounding resource depletion, creating inconsistency and moreover confusion among LCA practitioners. The evaluation of different life cycle impacts assessment (LCIA) methods done by EC JRC showed that available models did not address the same parameters: short- vs long-term, stock vs backup technology, etc. It also showed that if the correlation between the methods was sufficient for some resources, others such as rare earth elements showed a high level of inconsistency between methods. It was therefore necessary to develop a relevant indicator and harmonized assessment of impacts on resources in LCA. Furthermore, a resource strategy indicator based on the three pillars of sustainable development (economic, environmental and social) would better address wider challenges and making it a more powerful decision making tool. This study aimed to introduce an indicator for evaluating the strategy implications of metal resources for products and to compare different ways of production resulting from extraction of raw materials or recycling, with a special focus on rare earth materials. The indicator would assess the impacts based on a reserve-resource vision [BGS NERC] and the evolution over time and founded over three parameters: technical feasibility, economic viability and political stability (including social and environmental aspects) in representing countries.

Use of the boundary element method for the analysis of permeability tests in boreholes

This paper is concerned with the application of the boundary element method for the study of the shape factor, which is used for the determination of the soil permeability from field tests. In the first part of this paper, we present the methodology followed for the calculation of the shape factor using the boundary element method; its performance will be discussed through its comparison to a finite element modeling. This method is then used to analyze the influence on the shape factor of some parameters, mainly the lateral extension of the soil domain and the position of the cavity regarding the ground water table and the impermeable substratum. The last part includes a comparison of numerical and analytical results, which permits to suggest recommendations for the determination of the shape factor.

Application of lean to the bidding phase in building construction: a French contractor’s experience

Purpose While many procurement systems govern the construction sector, Design/Bid/Build is still prominent among the French building actors. The research applies Lean thinking (via a kaizen event) to the bidding phase of a building construction company to improve its bidding outputs. Design/methodology/approach The method used in this study is “Action-Research”. A two-month preparation phase was needed to prepare for the kaizen event. The results were based on an assessment conducted after 6 months of the kaizen event. Performance was measured following selected indicators related to ‘Time’, “Economical Impact”, “Quality” and “Sustainability”. Findings The Lean implementation had positive side-effects on the company’s organization and strategy as well. Practical implications The findings of this action-research project can be used to help researchers and practitioners assess the potential application of Lean in the bidding phase. It also provides insights into the importance of the cultural and existing practices for a successful Lean implementation. Originality/value A few research projects investigated the application of Lean thinking in bidding as it is considered as a wasteful process. However, waste can also be organized. The research proves that bidding can benefit from Lean thinking.

Experimental and numerical prototyping of a complex cement column formwork for construction

ABSTRACT Complex shapes in civil engineering require complex and unique molds. Starting from the fact that 3D printing technology primarily targets this type of product, this paper investigates the potential adaptation of 3D printing in the mold and formwork industry. A small-scale printing test was realized to build a complex architectural design prototype using cement. The results are presented according to three phases: 1 – Selection phase: 3D printing technology was selected and the adequate printing material. Experimental and numerical studies were realized to assess the material. 2 – Adaptation phase: the 3D printer was scaled for use. 3 – Prototyping phase, that deals with printing the formwork and evaluating the cement poles. The research proved the feasibility of using 3D printing technology to produce complex-shaped prototyped formworks for cement poles in construction.

Influence of enhancing electrolytes on the removal efficiency of heavy metals from Gabes marine sediments (Tunisia)

This study focused on the feasibility of the treatment of heavy metals-contaminated sediments from Gabes harbor (Tunisia) using enhanced electrokinetic process. It presented a laboratory short-time electrokinetic experiment. The enhancing agents, as citric, acetic acids and sodium dodecyl sulfate (SDS) were used regarding their low environmental hazard. The electrokinetic cell was specially designed in order to elaborate two experiments at the same time. This paper is composed of three parts. The first part introduces the characterization of Gabes sediments. The second part describes the design of laboratory electrokinetic cell and the followed methods. The third part is dedicated to the results analysis. Treatment efficiency revealed that more than 80% of lead was removed from Gabes marine sediments. The reduction of cooper concentration, in sediments after treatment, ranged from 74 to 87%. Despite, the high removal of cadmium that ranged from 58 to 79%, treated sediments presented Cd concentration above the threshold limit.

Automated non-contact NDT by ultrasonic surface waves

An automated ultrasonic scanner based on the non-contact air-coupled technique is designed and developed in order to perform nondestructive characterization of the surface of different structures and to detect the surface defects. The measurement is carried out without any contact with the examined part. The paper presents the scanner and several examples of its applications: the on-site characterization of concrete walls; the inverse analysis of concrete wall cover and the detection of surface defects on a steel sample and along old used railway rail.

Caractérisation et valorisation en technique routière de sédiments fluviaux pollués et traités

ABSTRACT This study deals with the valorisation of polluted river sediments, treated by the Novosol® process, in road materials. The first part concerns the physical, chemical, environmental and geotechnical characterisation of the Novosol® treated sediments (NTS). The results obtained show that NTS could be used in sub-based materials. Then, a formulation campaign was carried out with 5 different binders to study their compatibility with NTS and to evaluate the tensile strength and the Young modulus at 28 and 90 days of maturation. According to the “Guide des Traitements des Sols”, 3 of the studied binders could be used to valorize NTS in sub-based materials.

Improvement Insulating Properties of Ceramic Materials by Incorporating Additives

AbstractThe objective of this study is to improve the thermal performance of masonry bricks produced by the factory Briqueteries du Nord. This industrial plant is located in the north of France. The use of additives in the raw material admixture presents a promising approach for improving the thermal performance of building materials, and consequently to respond of requirements of the thermal regulation. Therefore, three additives are selected as part of an approach supporting sustainable development and waste valorization: flax shives, maize starch, and polystyrene beads. This experimental study is focused on the effect of these additives on the physical, mechanical, and thermal properties of ceramic samples. Different characterization tests were conducted at the laboratory scale. The results indicated that mixtures containing 2.5% flax shives or 7.5% starch ensured an optimal thermal performance, taking into account the mechanical strength of these products.