Recycled Wastes as Fibers for Concrete

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This research project aims to study the possibility to use recycled plastic wastes as fiber reinforcement for concrete elements, with the dual purpose to improve the structural performance of concrete and to create new opportunities for plastic waste revalorization and CO2 storage in the construction industry. Domestic wastes (bottles, carpets, food packaging) as well as industrial by-products will be considered. Concrete is the most used construction material, and one of the main responsible for materials and energy consumption, greenhouse gases emission, and waste production. In spite of this, concrete consumption is expected to continue to increase in the next decades, especially due to growing market in developing countries. Reducing the environmental impact of concrete is a fundamental issue to improve the sustainability of construction industry. Limiting the amount of cement is the most evident solution, but complementary strategies must be explored. The addition of fibers in concrete is a well-established practice to improve its structural performances. Depending on the type and amount of fibers that are used, fibers addition can: increase the strength and toughness of concrete; reduce the risk of early age cracking; limit drying shrinkage; contribute to crack control. The use of fibres allows to design structures which are thinner, lighter, more durable and which require a lower amount of traditional reinforcements, with an overall positive effect on the environment impact of concrete. However, fibers currently used in concrete are generally made with newly produced, high-tech materials, such as high-performance polymers (PP, PE, PVA), carbon, glass, or high strength steel. These materials are often manufactured abroad, which increases their economic and environmental cost. In several countries, a significant research effort is currently devoted to study the possibility to replace ordinary fibers with recycled fibers issued from wastes, such as plastics, bio-based plastics, textiles or natural wastes. Both domestic wasted (bottles, carpets, food packaging) as well as industrial by-products can be considered. Taking into account the large volume of concrete that is produced yearly, adding recycled waste fibers as a concrete component could represent a very efficient strategy to reduce the total volume of unvalued wastes and to allow long-time CO2 storage in building components. As documented in literature studies, however, the use of low-tech, low-performance recycled waste fibers in concrete might result in a degradation of its mechanical and durability performances, which can negatively affect the potential of the proposed recycling strategy. The purposes of this research idea is to identify, at the Swiss level, widely and locally available plastic wastes or plastic industrial by-products whose properties are suitable for use in concrete and which have the potential to improve its performances as a structural material, while creating new opportunities for waste revalorization and CO2 storage in construction industry.The phases of this research are:1. establish a state-of-the-art of plastic wastes and plastic by-products which:are widely available in Switzerland ;have no other recycling potential at present ;can be easily transformed (or are already) in the shape of short, discontinuous fibers with a length of 1 to 50 mm and a diameter of 0.1 to 2 mm ;are physically and chemically compatible with a use inside concrete ;have good mechanical properties. 2. based on results of point 1, identify 1-2 most promising types of fibers for application in structural concrete. 3. produce laboratory specimens with the identified types of fibers and with an adjusted mix-design; 4. characterize the structural performances of recycled waste fiber reinforced concrete with basic laboratory tests:mechanical properties: compression, tension, elastic modulus; rheologic properties : creep, shrinkage;properties related to durability: porosity, permeability, carbonation. The results of this preliminary project will serve as a basis to validate the potential of using locally available recycled waste fibers as an ingredient for structural concrete in Switzerland. In case of positive results, this research could be enlarged toward an industrial scale with the following steps : confirm the choice of recycled wasted fibres and the required preliminary treatement for optimal use in concrete ;optimize concrete mix-design to include recycled waste fibers;carry out laboratory tests on full-scale structural members made of recycled waste fibers concrete, such as beams in bending, slabs, columns;establish design and constructive rules for engineers;promote the industrialization of this recycling strategy.

Project Idea Metadata

• Project Idea Name: Recycled Wastes as Fibers for Concrete
• Date: 4/1/2022 2:56:34 PM
• Administrators:
  • Dario Redaelli

Project Idea Description

Concrete is the most used construction material, and one of the main responsible for materials and energy consumption, greenhouse gases emission, and waste production. In spite of this, concrete consumption is expected to continue to increase in the next decades, especially due to growing market in developing countries.

Reducing the environmental impact of concrete is a fundamental issue to improve the sustainability of construction industry. Limiting the amount of cement is the most evident solution, but complementary strategies must be explored.

The addition of fibers in concrete is a well-established practice to improve its structural performances. Depending on the type and amount of fibers that are used, fibers addition can: increase the strength and toughness of concrete; reduce the risk of early age cracking; limit drying shrinkage; contribute to crack control. The use of fibres allows to design structures which are thinner, lighter, more durable and which require a lower amount of traditional reinforcements, with an overall positive effect on the environment impact of concrete.

However, fibers currently used in concrete are generally made with newly produced, high-tech materials, such as high-performance polymers (PP, PE, PVA), carbon, glass, or high strength steel. These materials are often manufactured abroad, which increases their economic and environmental cost.

In several countries, a significant research effort is currently devoted to study the possibility to replace ordinary fibers with recycled fibers issued from wastes, such as plastics, bio-based plastics, textiles or natural wastes. Both domestic wasted (bottles, carpets, food packaging) as well as industrial by-products can be considered. Taking into account the large volume of concrete that is produced yearly, adding recycled waste fibers as a concrete component could represent a very efficient strategy to reduce the total volume of unvalued wastes and to allow long-time CO2 storage in building components.

As documented in literature studies, however, the use of low-tech, low-performance recycled waste fibers in concrete might result in a degradation of its mechanical and durability performances, which can negatively affect the potential of the proposed recycling strategy.

The purposes of this research idea is to identify, at the Swiss level, widely and locally available plastic wastes or plastic industrial by-products whose properties are suitable for use in concrete and which have the potential to improve its performances as a structural material, while creating new opportunities for waste revalorization and CO2 storage in construction industry.

The phases of this research are:

1. establish a state-of-the-art of plastic wastes and plastic by-products which:

• are widely available in Switzerland ;
• have no other recycling potential at present ;
• can be easily transformed (or are already) in the shape of short, discontinuous fibers with a length of 1 to 50 mm and a diameter of 0.1 to 2 mm ;
• are physically and chemically compatible with a use inside concrete ;
• have good mechanical properties.

2. based on results of point 1, identify 1-2 most promising types of fibers for application in structural concrete.

3. produce laboratory specimens with the identified types of fibers and with an adjusted mix-design;

4. characterize the structural performances of recycled waste fiber reinforced concrete with basic laboratory tests:

• mechanical properties: compression, tension, elastic modulus;
• rheologic properties : creep, shrinkage;
• properties related to durability: porosity, permeability, carbonation.

The results of this preliminary project will serve as a basis to validate the potential of using locally available recycled waste fibers as an ingredient for structural concrete in Switzerland.

In case of positive results, this research could be enlarged toward an industrial scale with the following steps :

• confirm the choice of recycled wasted fibres and the required preliminary treatement for optimal use in concrete ;
• optimize concrete mix-design to include recycled waste fibers;
• carry out laboratory tests on full-scale structural members made of recycled waste fibers concrete, such as beams in bending, slabs, columns;
• establish design and constructive rules for engineers;
• promote the industrialization of this recycling strategy.

This research project aims to study the possibility to use recycled plastic wastes as fiber reinforcement for concrete elements, with the dual purpose to improve the structural performance of concrete and to create new opportunities for plastic waste revalorization and CO2 storage in the construction industry. Domestic wastes (bottles, carpets, food packaging) as well as industrial by-products will be considered.