Recycling of rubber waste in sand concrete

The large development in the consumption of rubber is observed in the recent years, which leads to an increase of the production of rubber related waste. Rubbers are not hazardous waste, but they constitute a hazard for both environment and health, in case of fire in storage sites. So, recycling appears as one of the best solutions for disposing of rubber waste.This paper presents an experimental investigation dealing with the valorisation of rubber waste, specifically rubber obtained from old shoes sole waste. The waste rubbers are used form (0/5 mm) to mixes as addition at percentage (10%, 20%, 30% and 40%) in sand concrete. The physical (workability, bulk density), mechanical (compressive and flexural strength) and thermal properties are studied and analysed.The results indicate that the incorporation of rubber waste particles in sand concrete contributes to increase the workability and reduce the bulk density of all studied sand concrete. The obtained results show that mechanical performance (compressive and flexural strength) decreases when the rubber content increases. Nevertheless, the presence of rubber aggregate leads to a significant reduction in thermal conductivity, which improves the thermal insulation performances of sand concrete. This study insures that reusing of recycled rubber waste in sand concrete gives a positive approach to reduce the cost of materials and solve some environmental problems

Assessment of fluidity retention, mechanical strength and cost production of blended cement self-compacting concrete using the concept of a performance index

Construction industry consumes a large amount of natural resources and energy and produces high amount of CO2 emissions and waste materials. For more sustainable construction industry, various waste materials are used as natural aggregates substitution or as cement replacement materials. In this paper, marble powder (MP) is used as a substitution to ordinary Portland cement and its effects on some fresh and  hardened properties of self-compacting concrete (SCC) are investigated. The tests at the fresh state were slump flow, L-box and sieve segregation. To assess the fluidity retention, slump flow loss was measured after 30, 60 and 90 minutes. At hardened state, two tests were realized: compressive strength and static segregation. The results indicate that adding MP improved the fresh properties, but decreased the compressive strength of SCC. Adding MP allows to maintain the fluidity of SCC until 90 minutes. Production cost can be reduced by using MP. The performance approach showed that a substitution level of MP of 20% is adequate to produce an eco-efficient SCC with high fluidity and acceptable strength

Mass transfer modelling of the extraction of antibiotics from aqueous solution using Biosurfactants

International audienceThe objective of this work is to modelling a new separation technique based on the removal of antibiotics such as amoxicillin and ampicillin produced by antibiotical company Saidal Médéa (Algeria) from pharmaceutical effluents using biosurfactants and commercial surfactants. The kinetic distribution of amoxicillin and ampicillin between the two phases was modelled in order to well understand the mechanism governing the direct transfer of antibiotics from the aqueous phase to the micellar phase. The results were interpreted in terms of a two-film theory for flat interface. The model of the kinetic transfer developed in this study provides excellent predictions. A very good correlation between predicted and experimental values was found : R2 = 0.98 for the sorption onto biosurfactant and R2 = 0.99 onto a synthetic surfactant. The model coefficients were used to estimate the overall combined mass transfer coefficient and the individual mass transfer coefficients

Strength and durability of low-impact environmental self-compacting concrete incorporating waste marble powder

This research studies the effect of waste marble powder (WMP) as substitute of Portland cement on strength and durability of self-compacting concrete (SCC) in order to produce SCC with reduced impact environmental. For this purpose, five mixtures were designed in which four mixtures contained WMP at substitution levels of 5, 10, 15, 20%, and mixture included only the Portland cement as control mix. The realized tests are compressive strength at 3, 7 and 28 days, water capillary absorption, water absorption by immersion and sulfate attack. The results show a reduction in the compressive strength with increasing WMP content. The use of WMP was found to increase both of the water capillary absorption and water absorption by immersion. SCC containing WMP subjected to magnesium sulfate attack presented a lower expansion and higher resistance to sulfate aggressions

Measuring and evaluating financial performance using modern and traditional indicators and studying their effectiveness in creating value Acase study of the Saidal complex during the period 2009-2019

تسعى هذه الدراسة إلى تقييم وقياس الأداء المالي بواسطة المؤشرات التقليدية ممثلة في (BFR, ROE, ROA, ROI, EPS, ROS)،والمؤشرات الحديثة ممثلة في القيمة الاقتصادية المضافة EVA والقيمة السوقية المضافة MVA، مع تحديد مدى قدرتها وفعاليتها في تفسير الأداء المالي، وقد قمنا بتحليل الوضعية المالية لمجمع صيدال خلال الفترة 2009-2019 والتي تنشط في بورصة الجزائر، مع دراسة إحصائية للعلاقة بين المؤشرات التقليدية والحديثة، فقد أظهرت الدراسة أنه ناك بعض المؤشرات التي لها علاقة ذات دلالة إحصائية بينه اوبين القيمة الاقتصادية المضافةThis study aims to evaluate and measure financial performance using traditional indicators represented in (BFR, ROE, ROA, ROI, EPS, ROS), and modern indicators represented in EVA and MVA, while determining their ability and effectiveness in explaining financial performance. We have analyzed the financial position of Saidal complex during the period 2009-2019, which is active in the Algiers Stock Exchange, with a statistical study of the relationship between traditional and modern indicators.The study showed that there are some indicators that have a statistically significant relationship between them and the economic value adde

The Effect of Ceramic Wastes on Physical and Mechanical Properties of Eco-Friendly Flowable Sand Concrete

This work aims to study the valorization and recycling of ceramic wastes (wall tiles) as a fine aggregate instead of sand in the manufacturing of flowable sand concrete (FSC). For this, the sand is substituted with the ceramic wastes at different dosages (0, 5, 10, 15, 20, and 25% by volume of the sand). The influence of the ceramic wastes addition on the physical (workability, density) and mechanical (compressive, flexural and elastic modulus) properties of FSC was studied. The results show that the use of ceramic waste as partial replacement of sand contributes to reduce the workability, bulk density and improves the mechanical strengths of FSC according to the use of 25% of wall tiles waste

Surfactants-based remediation as an effective approach for removal of environmental pollutants—A review

Deterioration of environmental quality and equilibrium by rampant industrial expansion, accelerated urbanization and unchecked population growth has become a high-priority concern. The release of an alarming number of toxic polluting agents such as volatile organic compounds, dyes, heavy metals, pharmaceuticals, pesticides, industrial wastes, and personal care products due to natural or anthropogenic activities pose direct adverse effects on human health and living entities. This issue is inescapably increased because of the lack of efficient technologies for the proper disposal, management, and recycling of waste. It is of paramount importance to track alternative solutions to address these pollution problems for an eco-sustainable environment. Conventional remediation techniques are either inefficient, cumbersome or restricted due to certain techno-economic limitations. Environmental compatibility and high pollutant-removal efficacy make surfactants valuable for removal of organic pollutants and toxic heavy metal ions from different mediums. In this review, we present recent and up-to-date information on micelles/surfactants-assisted abatement of a vast number of toxic agents of emerging concern from water/wastewater including volatile organic compounds, personal care products, pharmaceutically active residues, toxic metals, dye pollutants, pesticides, and petroleum hydrocarbons. Based on the literature survey, it can be concluded that micelles-assisted water and soil treatment technology can have a better future on large-scale decontamination of wastewater. Though bio-surfactants are environmentally friendlier matrices and have successfully been employed for environmental decontamination; their large-scale applicability is challenging owing to high costs. Additional research efforts on the development and employment of novel bio-surfactants might render wastewater treatment technology greener, smarter and economical

Experimental Study on the Thermal Behavior of Exterior Coating Textures of Building in Hot and Arid Climates

The building envelope is the barrier between the interior and exterior environments. It has many important functions, including protecting the interior space from the climatic variations through its envelope materials and design elements, as well as reduction of energy consumption and improving indoor thermal comfort. Furthermore, exterior building sidings, in addition to their aesthetic appearance, can have useful textures for reducing solar gains and providing good thermal insulation performance. This research examined and evaluated the effect of external siding texture and geometry on energy performance. For this objective, a field in situ testing and investigation of surface temperature was carried out on four samples (test boxes) with different exterior textures and different orientations, under the climate zone of Constantine–Algeria during the summer period. The results indicated significant dependability between the exterior texture geometry, the percentage of shadow projected, and external surface temperature. The second part of the research involved a similar approach, exploring the effect of three types of particles with the same appearance but with different thermal characteristics. It was concluded that the natural plant aggregates “palm particles” had the best performance, which contributed to a significant reduction of external surface temperature reaching 4.3 °C, which meant decreasing the energy consumption

From Learners to Researchers: Exploring Algerian EFL Graduate Students’ Autonomy in Dissertation Writing

Abstract: This research paper calls for a deeper exploration of learner autonomy in the context of writing dissertations in English as a Foreign Language (EFL). Achieving university-level research requires advanced abilities to overcome complex research-related challenges while adhering to strict academic standards and expectations. Consequently, fostering Learner Autonomy (LA) among graduate students becomes crucial. This study investigated the perspectives of EFL Algerian teachers and students on LA, employing four distinct lenses: the understanding and significance of LA, autonomy levels and readiness to engage in research, challenges faced in maintaining autonomy during the dissertation writing process, and strategies for developing LA among student writers/researchers. To this end, a randomly selected sample of 65 respondents from six Algerian universities across diverse regions of the country (north, west, south, and east) participated in an online questionnaire. The data was then analyzed using both quantitative and qualitative methods. The findings allowed for framing LA from the participants’ perspectives and identifying different practices to promote autonomous learning as students progress from mere learners to researchers. Based on the data discussed, this study offered implications for key stakeholders in higher education. Keywords: Learner autonomy, thesis/dissertation writing, research, graduate students, higher educatio