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Can concrete blocks be made with recycled materials?
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Sustainability has become an increasingly important consideration in the construction industry, with architects, developers and contractors all looking for ways to reduce the impact of new buildings on the environment. Building materials play a significant role in that effort, particularly concrete, which has traditionally been viewed as a resource-intensive material.
But can concrete be made more sustainable through the use of recycled materials? In this article, we look at how recycled content is being incorporated into concrete blocks, the materials that can be used and how products such as the Lignacite ECO Range are helping to reduce environmental impact without compromising on performance.
Standard concrete vs eco concrete
Concrete has been used in some form since ancient times, with the earliest estimates putting its introduction as far back as 1400 BC. It has evolved considerably over the years, with one of the most significant developments being the introduction of Portland cement. Invented in the 19th century, Portland cement is typically manufactured using limestone and clay or shale, which are heated to high temperatures and ground into a fine powder. When mixed with water, it forms cement paste. When this paste is combined with aggregates such as sand and gravel, it becomes concrete.
Cement is, therefore, a key component in concrete manufacture. Although the production of cement has traditionally been seen as carbon extensive, the UK concrete and cement sector has cut carbon emissions by more than 50% since 1990.
However, modern developments have given rise to sustainable alternatives, often referred to as 'eco concrete' or 'green concrete'. These terms can have different meanings depending on the product. They may describe concrete containing recycled materials, concrete manufactured using lower-carbon production methods, concrete incorporating alternative binding materials, or concrete designed to reduce environmental impact throughout its lifecycle.
Providing they are manufactured to a high standard using suitable materials, both conventional and eco concrete blocks are suitable for a wide range of construction projects. However, eco concrete alternatives can offer environmental advantages, including reduced embodied carbon, lower demand for virgin resources and increased use of recycled materials.
What recycled materials can be used in concrete blocks?
A range of recycled materials can be used to produce concrete and concrete blocks, supporting the circular economy.
Fly ash: Historically one of the most widely used secondary materials in concrete manufacture, fly ash can fill microscopic voids within the mix, improving strength and reducing permeability.
Furnace bottom ash: This is derived from coal-burning power stations as well as from other industrial processes. Although less plentiful in supply, it remains an important lightweight aggregate for concrete block production.
Wood particles: Lighter than many traditional aggregates, wood particles can help reduce the weight of concrete blocks, making them easier to handle. Wood fibres are also porous and contain air, which can help reduce thermal conductivity.
Recycled glass: This waste material can be used to replace a proportion of the sand or cement used in concrete blocks. It is hard, durable and chemically stable, making it suitable as a partial replacement for sand. Foamed glass aggregate, created by milling glass into fine particles and combining with a foaming agent, is emerging as a versatile raw material with wide ranging applications including use in concrete blocks.
Construction and demolition waste: Recycled and crushed concrete can be processed and reused as aggregates in new concrete products because they already possess many of the characteristics required.
What recycled materials are used in Lignacite's ECO Range?
At Lignacite, we use recycled sand and graded wood particles within our ECO Range. These materials have been carefully selected to balance sustainability with the technical requirements of modern construction.
Recycled sand helps reduce reliance on virgin raw materials, while graded wood particles contribute to lower density and improved thermal qualities.
By combining these materials, the Lignacite ECO Range delivers high levels of recycled content without compromising on the performance characteristics expected from concrete masonry blocks.
Do recycled materials affect the quality and strength of concrete?
Most modern concrete products are subject to rigorous testing and quality control procedures, regardless of whether they contain recycled content. This ensures they meet the strength, durability and performance requirements expected for their intended use.
Lignacite ECO blocks have been developed to balance sustainability with technical performance. They have been independently tested to ensure they meet the relevant strength and durability benchmarks for construction use, demonstrating that the use of recycled materials does not have to come at the expense of quality.
Meeting industry standards with recycled materials
As highlighted above, eco concrete blocks can be tested to ensure they meet the required standards for quality, strength and durability. The inclusion of recycled materials does not remove the need for rigorous testing or compliance with industry requirements.
When selecting concrete blocks containing recycled content, it is worth checking whether the manufacturer holds recognised certifications. For example, Lignacite blocks are certified to the BS EN 771-3 quality standard for aggregate concrete masonry units. They also have UKCA marking, which indicates that our products have been assessed and meet the requirements for sale within the UK. Together, these certifications help demonstrate that our products are suitable for use in construction.
If sustainability is a consideration for your next project, it is also important to review a chosen product's Environmental Product Declaration (EPD). EPDs provide independently verified information about a product's environmental impact, helping specifiers compare materials and make informed decisions. Responsible sourcing certifications, such as BES 6001, can provide additional confidence that the materials used within a product have been sourced responsibly and in accordance with recognised industry standards.
What are the benefits of using recycled materials in construction?
Using recycled content offers many benefits. By incorporating waste and secondary materials into new products, manufacturers can divert material from landfill while reducing reliance on virgin raw materials. This helps conserve natural resources and can contribute to lower embodied carbon.
For projects targeting sustainability objectives, building materials containing recycled content can make a valuable contribution. Depending on the wider specification, they may support credits under assessment frameworks such as BREEAM and LEED, helping project teams demonstrate their commitment to responsible material selection and environmental performance.
At Lignacite, recycled aggregates have been incorporated into concrete blocks since 1947, when the use of secondary materials in construction products was less common than it is today. Building on this heritage, the Lignacite ECO Range was launched in 2025. It contains up to 70% recycled content and offers up to 70% lower embodied carbon than standard blocks while maintaining the performance expected of standard concrete masonry units.
The recycled content within the Lignacite ECO Range has been independently verified by sustainability consultants Blue Marble, while environmental data is published through third-party verified Environmental Product Declarations (EPDs). This provides transparent, independently assessed information to support specification decisions.
Read more: Everything you need to know about recycled aggregates
Helping build a greener construction landscape
Concrete blocks can be successfully manufactured using recycled materials while maintaining the strength and durability required for modern construction. By reducing reliance on virgin raw materials and diverting waste from landfill, these products can support more sustainable building practices.
If you're considering incorporating lower-carbon building materials into your next project, explore the Lignacite ECO Range to compare products, download technical information and use our Carbon Saving Calculator to see the potential impact on your next project.
