Valorisation de nouveaux matériaux naturels et recyclés dans la construction routière en Algérie

Résumé

Le développement du secteur des travaux publics en Algérie réclame des quantités très importantes de granulats. L’extraction abusive et anarchique des matériaux mène à l’amenuisement des sources naturelles habituelles, notamment des gisements alluvionnaires. En plus des effets néfastes sur l’environnement, cette surexploitation menace sérieusement l’approvisionnement des projets. Ainsi, l’exploitation de nouvelles sources de granulats paraît sans doute une solution d’avenir. En effet, plusieurs matériaux naturels (schistes, marnes,…) et recyclés (débris de béton, débris de verre,…) peuvent faire l’objet de recherches dans ce domaine, vu leur disponibilité et leur facilité d’extraction en Algérie. Par ailleurs, leur exploitation, peut être très intéressante tant sur le plan économique et environnemental. L’étude expérimentale réalisée s’inscrit dans ce contexte. Elle a pour objectif, la valorisation de la marne et des débris de verre dans la construction routière. Elle consiste à préparer des échantillons en mélanges de marne avec différentes proportions de verre et à étudier après identification, leur comportement sous les principaux essais mécaniques routiers. Les résultats obtenus sont très remarquables. En effet, contrairement au comportement défavorable que présentent la marne ou le verre seuls, leur combinaison offre par contre, des mélanges avec des comportements très intéressants. Particulièrement, les mélanges à 20% de verre ont présenté une très bonne aptitude au compactage, avec des résistances au poinçonnement et au cisaillement très importantes. Ces mélanges ont montré également des résistances très acceptables à la fragmentabilité, à la dégradabilité, aux chocs et à l’usure. Ce qui vérifie amplement les exigences des normes pour une utilisation dans les couches de chaussées.

Abstract

These recent years, the development of the civil engineering and especially the public works sectors in Algeria requires large amount of aggregates. Therefore, the abusive uncontrolled extraction of materials send out distress signals on the over-exploitation and reduction of the usual natural sources of aggregates, particularly alluvial deposits. Indeed, this can certainly maximize the risks of environmental contamination and threaten the aggregates supply continuity of projects, therefore seriously disturbing the development of the public work sector. For those reasons, the exploitation of new aggregates sources and the search for new local materials (natural or recycled materials) are urgently needed and seem to be a promising solution for sustainable development. Indeed, many natural materials such as (schist, marl,…) have been investigated in this area, given their availability and ease of extraction. Also, tons of inert wastes (concrete debris, glass debris,…) are generated from various human activities and abandoned in nature (along the roads) or buried in landfills where they surely represent contamination threats to ground water, while, these materials can be recovered and reused as alternative aggregates in important industrial sectors such as civil engineering and public works. The present experimental study is conducted in this context. It aims at valorizing local natural materials (marl) and recycled materials (glass debris) in road construction. Indeed, marl is among the most available materials in Algeria, it represents over 40% of the soils of Great Kabylia (Tizi-Ouzou). It is close to the surface (accessibility), with thicknesses exceeding 1000 meters (availability). Glass debris are also among the most available types of wastes (found in dumps and landfills). It is widely used in many industrial activities such as packaging, decoration, construction, and therefore it generates a lot of inert waste which take about 5000 years to decompose. For those reasons (large amounts and lengthy decomposition), several studies have been carried out for the glass possible reuse in civil engineering, especially in concrete and roads. To achieve this work, samples are prepared in the form of mixtures of marl with different proportions of glass debris (0, 10, 20, 30 and 40%). They are then submitted after identification to the main mechanical road tests, namely: compaction with modified Proctor tests in order to assess their maximal dry density, penetration with CBR tests (California Bearing Ratio) to evaluate puncture strength immediately under the circulation of vehicles during the construction of pavements or after soaking under water for 4 days (96 h), representing the worst humidity conditions on construction site. The samples are then subjected to direct shear tests using Casagrande shear box to assess their shear strength under traffic, especially during acceleration and braking of heavy vehicles. Finally, they are subjected to fragmentability, degradability, Los Angeles and micro-Deval tests to evaluate the evolution of the grains under different mechanical efforts (traffic, climatic and hydro-geological conditions). The experiments carried out have shown very remarkable results. Unlike the unfavorable behavior showed by the marl or the glass alone; their combination as mixtures presents very interesting mechanical characteristics under the different tests. Particularly, the mixtures with 20% of glass debris have shown the best aptitude to compaction, at low water content, and a high penetration strength in soaked and un-soaked conditions. In addition, it exhibits very interesting mechanical characteristics at shearing, with acceptable fragmentability, degradability, impact and wear behaviors. These results are very valuable and fully satisfy the requirements of standards for materials used in roads under weak and medium traffic. However, to better understand and develop the use of the studied materials in the road construction; further tests are necessary, such as long-term tests under cyclic natural loading (temperature, freeze–thaw,…). This research work may have considerable interests, both on the economical aspect and on the environmental impact in the region, mainly:

• Conservation of alluvial deposits and exploitation of new sources of aggregates to ensure the projects supply.

• Preservation of the environment by recovering abandoned glass wastes in nature, consequently, allowing the recovering of important storage spaces and significantly reducing the needs for new landfills.

• Contribution to the development of the recycling industries and the creation of more employment opportunities for the local population, leading to income generation and poverty reduction in developing countries such as Algeria, which offers a fertile field of recyclable materials (concrete, plastic, glass,…).

However, this study must be accompanied by appropriate and selective dumps installation strategies, with a large sensitizing of population in order to allow the easy collection of glass debris and other materials that can be recycled in the civil engineering field and other construction fields.