VBD - Villes et Bâtiments Durables

Ecoconstrucion with Concrete Recycling – ECOREB

Ecoconstruction with concrete recycling

Waste materials from construction can represent an important source of material in the civil ingineering field. The recycled materials from waste concrete of buildings and used as components of new concretes can be considered todays as new environmental, economic and technological perspectives. Its implementation needs to remove scientific and technical issues which are addressed in project ECOREB.

Recycling waste concrete in concrete: environmental and economic issues

Management of construction waste is an important issue for the construction industry because it must meet the requirements of sustainable development and particularly that related to the environmental impact. Reuse of recycled demolition / deconstruction materials can limit the extraction of raw materials and thus contribute to the preservation of natural aggregate deposits whose exploitation is increasingly complex and subject to strong regulatory constraints. Waste recycling from construction site also reduces energy and environmental impacts related to transportation. It is also an important economic issue because this issue is becoming more prevalent in the market.<br /><br />The construction sector, increasingly sensitive to issues related to the preservation of the environment, are working on the future of concrete at the end of life of buildings. A total of about 300 million tons of building waste are produced each year in France. Among this construction waste, only a small portion of concrete is recycled, mainly for road construction. However, in other European countries, recycled concrete from the deconstruction crushed aggregates are already used in the formulation of new concrete.<br />ECOREB project aims primarily to change the trend at the national level, addressing scientific issues associated with the use of crushed concrete aggregate as constituent of new concrete. This project is part of the national research RECYBETON (complete recycling of concrete), whose objective is to find a solution to recycle each cubic meter of concrete deconstructed as a direct or indirect concrete component.

ECOREB project is structured around three areas of research: (i) water and recycled materials, (ii) mechanical behavior of concrete with recycled aggregates and (iii) durability.

The objective of the topic «water and recycled materials« is to develop methodologies to quantify the impact of process of saturation / desaturation of the recycled characteristics of fresh concrete and hardening materials: the rheology of fresh concrete time handling, the plastic shrinkage behavior and the risk of cracking associated to the changes in the micro and meso structure while curing. This line of research will lead to recommendations for the formulation of concrete made from recycled materials, recommendations for the treatment of fresh concrete and mastery of plastic shrinkage and cracking associated.

On the mechanical behavior of recycled concrete, previous studies have shown that existing models (Eurocode, ACI codes, CEB or Chinese) can not be applied to concrete with recycled aggregates and that such differences are observed for high rates of substitution. The objective of this line of research is to develop models to determine the relationship between the mechanical properties. This is to develop a macroscopic model (elasto-viscoplastic damageable) to describe the behavior of recycled concrete under monotonic loading, cyclic and deferred based on an experimental approach

The objective of the issue «sustainability« is to evaluate the influence of aggregates from recycling on the performance of concrete durability. It is studying the parameters controlling the corrosion of reinforcement (carbonation and chloride ion migration), the design of coatings of concrete with recycled aggregates, resistance to freeze / thaw, durability indicators and evolution of microstructure using recycled aggregates.

Expected Results:
- Proposal for a methodology to characterize the absorption
- Recommendations for the formulation of concrete using recycled materials with controlled rheology and few sensitive to drying phenomena
- Recommendations for the treatment of fresh concrete and mastery of plastic shrinkage and cracking associated
- Proposals for relations in the Eurocodes
- Model behaviour implemented in a computer code for structural design
- Tools to estimate lifetime under static loading
- Model prediction of fracture sharp crack under monotonic and / or cyclic loadings
- Behaviour of concrete with recycled aggregates linked to the carbonation and chloride migration
- Calculation of reliability parameters for concrete incorporating recycled aggregates and compared with values ??obtained with the conventional concrete
- Analysis of possible changes to coatings given in the Eurocodes in the case of concrete containing recycled aggregates
- Study of the influence of parameters of microstructure on the resistance
- Model prediction of thermo-hydro-mechanical behaviour of concrete recycled aggregates at low temperature
- Quantification of indicators of durability / comparative analysis with the measured values ??of the traditional concrete
- Characterization of the microstructure of concrete with recycled aggregates
- Analysis of the effects of internal curing in terms of potential profits on the durability of concrete

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In the context of demolition programs which are growing rapidly, particularly in the framework of major urban projects, ECOREB (Eco construction with concrete recycling) aims at dealing with recycling issues in the field of construction waste for the future sustainable city. Among the building wastes, only a part of concrete from demolition is currently recycled, mainly for road construction. Recovery of all of these materials as components for the production of recycled concrete is now opening up new environmental, economical and technological prospects but needs to overcome scientific and technological brakes.
Reuse of recycled aggregates from demolition / deconstruction can limit the extraction of raw materials and thus contribute to the preservation of natural aggregates. It deals thus primarily with environmental issues. The use of recycled aggregates for the development of new concrete is part of a commitment to sustainable development, partly due to expectations of the “Grenelle de l’Environnement” in France and European regulations. Note also that waste management of building is also a growing market.
ECOREB is an industrial research complementary to the National Project RECYBETON. It proposes overcoming fears about the use of recycled aggregates from concrete in the building industry to produce new concretes, using largely experimental results. ECOREB aims, also, at developing new tools dedicated to the study of the water demand due to the presence of cement mortar embedded to aggregates. Moreover ECOREB will make possible the characterization of the interfaces quality between (1) the new concrete and the recycled aggregate and (2) the recycled mortar and the natural aggregate. It also aims at providing a tool for predicting recycled concretes characteristics and especially their behavior under external stresses (mechanical loads, snow, corrosive atmospheres, ...) and under internal stresses (shrinkage, change in humidity or heat of concrete hydration ) and to establish empirical relationships between mechanical parameters and indicators of sustainability in relation to the microstructure which depends on water demand.
To achieve these objectives the scientific program is divided into three technical tasks that interact and complement each other.
The first "Water and recycled materials" provide recommendations on the formulation of concrete made from recycled materials, the curing of young concrete and the plastic shrinkage phenomenon as well as the associated cracking.
The second "Study of mechanical behavior of recycled concrete under static, cyclic, creep and relaxation loadings" will characterize the mechanical behavior of recycled concrete and establish empirical models incorporating microstructural effects. These models will be used by building industry actors to predict the lifetime of the recycled concrete.
The third task "durability" will evaluate the freeze / thaw resistance and long-term behavior of concrete recycled regarding to corrosion, chlorides migration and steel corrosion risk. Durability indicators will be assessed. Water and curing effects will be treated.
Results of ECOREB will lead to a breakthrough on the reuse of demolished concrete as components of new concrete and, ultimately, to a way in which the use of recycled aggregates in concrete will become part of everyday practices.

Project coordination

Brice DELAPORTE (Institut pour la Recherche appliquée et l'Expérimentation en Génie Civil) – brice.delaporte@irex.asso.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

ARMINES ARMINES - CMGD_DGCE
IFSTTAR Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux
GeM Institut de Recherche en Génie Civil et Mécanique
CERIB Centre d'Etudes et de Recherches de l'Industrie du Béton
L2MGC Laboratoire de Mécanique et Matériaux du Génie Civil
IREX Institut pour la Recherche appliquée et l'Expérimentation en Génie Civil

Help of the ANR 729,931 euros
Beginning and duration of the scientific project: November 2012 - 48 Months

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