The construction industry is one of the largest consumers of natural resources and one of the biggest producers of waste in the world. According to the World Bank, the sector accounts for about 36% of the global energy use and 40% of the carbon dioxide emissions. Moreover, the sector generates about 1.3 billion tons of solid waste per year, which is expected to rise to 2.2 billion tons by 2025.
However, there is a potential solution to this environmental challenge: recycling and reusing the waste materials from construction and demolition (C&D) activities, as well as from agricultural production. A team of researchers from Germany’s Fraunhofer Institute for Wood Research has developed innovative building materials that combine C&D waste and plant-based waste, such as natural fibers, wood chips, rice husks, and straw. These materials could make the construction industry more sustainable, efficient, and cost-effective.
Recycled Concrete from C&D Waste and Plant Waste
One of the main products of the research team is recycled concrete, which is made of a mixture of concrete and masonry waste, and plant waste. The plant waste acts as a reinforcement for the concrete, improving its strength and durability. The team also used ash from burnt rice husks as a substitute for cement, reducing the need for mining and processing of raw materials.
The recycled concrete has several advantages over conventional concrete, such as:
- Lower environmental impact: The recycled concrete reduces the amount of waste that goes to landfills, and the greenhouse gas emissions from the production of cement and aggregates. It also saves energy and water in the manufacturing process.
- Higher performance: The recycled concrete has similar or better mechanical properties than conventional concrete, such as compressive strength, flexural strength, and modulus of elasticity. It also has lower thermal conductivity, which means it can provide better insulation and energy efficiency.
- Lower cost: The recycled concrete is cheaper than conventional concrete, as it uses waste materials that are readily available and have low or negative value. It also reduces the transportation and disposal costs of the waste materials.
The following table summarizes some of the properties and benefits of recycled concrete compared to conventional concrete.
| Property | Conventional Concrete | Recycled Concrete |
|---|---|---|
| Density (kg/m3) | 2400 | 2000 |
| Compressive strength (MPa) | 30 | 35 |
| Flexural strength (MPa) | 4 | 5 |
| Modulus of elasticity (GPa) | 30 | 28 |
| Thermal conductivity (W/mK) | 1.8 | 0.8 |
| CO2 emissions (kg/m3) | 300 | 150 |
| Cost (USD/m3) | 100 | 80 |
Insulation Material from Plant Waste
Another product of the research team is insulation material, which is made of plant-based waste products, such as sawdust, rice and wheat straw, and flax fibers. These materials are processed and bonded together to form insulation boards, which can be attached to the recycled concrete components to create insulated walls.
The insulation material has several advantages over conventional insulation materials, such as:
- Lower environmental impact: The insulation material uses renewable and biodegradable resources, which reduce the dependence on fossil fuels and the generation of plastic waste. It also reduces the energy consumption and emissions from the production and transportation of the insulation materials.
- Higher performance: The insulation material has similar or better thermal and acoustic properties than conventional insulation materials, such as mineral and glass wool, or polystyrene. It also has higher fire resistance and moisture resistance, which enhance the safety and durability of the building.
- Lower cost: The insulation material is cheaper than conventional insulation materials, as it uses waste materials that are abundant and have low or negative value. It also reduces the installation and maintenance costs of the insulation materials.
The following table summarizes some of the properties and benefits of insulation material compared to conventional insulation materials.
| Property | Conventional Insulation Materials | Insulation Material |
|---|---|---|
| Density (kg/m3) | 10-50 | 100-200 |
| Thermal conductivity (W/mK) | 0.04-0.05 | 0.05-0.06 |
| Sound absorption coefficient | 0.8-0.9 | 0.9-1.0 |
| Fire resistance | Low-Medium | High |
| Moisture resistance | Low-Medium | High |
| CO2 emissions (kg/m3) | 10-20 | 5-10 |
| Cost (USD/m3) | 20-40 | 10-20 |
Applications and Implications
The recycled concrete and insulation material developed by the research team have various applications in the construction industry, such as:
- Residential and commercial buildings: The materials can be used to construct walls, floors, roofs, and other structural and non-structural elements of buildings, providing high-quality, energy-efficient, and affordable housing and facilities.
- Infrastructure and public works: The materials can be used to construct bridges, roads, dams, and other civil engineering projects, enhancing the resilience, durability, and safety of the infrastructure.
- Reconstruction and humanitarian aid: The materials can be used to rebuild areas affected by natural disasters, wars, or conflicts, using the local waste resources and reducing the dependence on external aid and imports.
The use of recycled concrete and insulation material could have significant implications for the environment, the economy, and the society, such as:
- Reducing the environmental impact of the construction industry, by saving natural resources, lowering greenhouse gas emissions, and minimizing waste generation and disposal.
- Improving the performance and efficiency of the buildings and infrastructure, by increasing their strength, durability, insulation, and safety .
- Lowering the cost and increasing the accessibility of the construction materials, by using waste materials that are cheap and available, and reducing the transportation and disposal costs .
- Creating new opportunities and jobs in the waste management and recycling sector, by stimulating the demand and supply of the waste materials and the recycled products.
- Enhancing the social and humanitarian aspects of the construction sector, by providing better living and working conditions, and supporting the reconstruction and development of the affected areas.
