Crumb Rubber Concrete, CRC
The Problem
In February 2022, the Aggregate and Sand Producers Association of Southern Africa (ASPASA) made a notable statement, calling for a reduction in mining activities to combat the damaging effects of illegal sand mining in South Africa. Unregulated sand extraction has led to environmental hazards, such as unsafe pits that endanger both humans and animals, while the lack of effective law enforcement has allowed these operations to grow in scale and sophistication. ASPASA highlights that legal mining operations, which adhere to strict environmental, social, and governance (ESG) standards, face unfair competition from illegal miners who evade these regulations. These legally regulated operations are required to meet stringent environmental and safety standards, regularly undergo inspections by the Department of Mineral Resources and Energy, and bear the significant costs of compliance. However, the higher costs associated with legal mining often drive demand toward illegally sourced sand, despite the long-term unsustainability of such operations.
Sand plays a crucial role in providing concrete with the required consistency and chemical properties. However, global reserves of sand are becoming increasingly depleted. The escalating pace of construction in infrastructure, including roads, buildings, and industrial projects, has led to a growing demand for sand. This heightened demand has compelled mining companies to exploit natural ecosystems, particularly those located in sandy habitats such as beaches and riverbeds, resulting in significant environmental degradation.
The Solution
Rubber is an essential material used in various industrial sectors. Rubber can be repurposed in numerous applications, including road construction, water barriers, geotechnical uses, retaining walls, and as an additive in concrete mixes. One promising approach is incorporating rubber from waste tires into concrete mixes as a partial replacement for fine or coarse aggregates, creating what is known as crumb rubber concrete (CRC). Studies have shown that adding rubber to concrete enhances properties such as ductility, energy dissipation, and sound absorption​
Sound Insulation
Thermal Insulation
Acid Resistance
CRC is economical and simple to produce, with good resistance to acid and low water absorption. While it has lower strength compared to traditional concrete, it can be utilised in applications where strength is not the primary concern, allowing its other beneficial properties to be exploited. CRC can be used for architectural purposes such as nailing concrete, pedestrian pavements, precast roofs in green buildings, jersey barriers, and skid-resistant ramps.
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It is also well-suited for lightweight applications, including architectural features, building facades, and decorative elements. Furthermore, rubberised concrete performs well in environments with significant temperature fluctuations, such as in freezing and thawing conditions, and can be used in sports courts, airport waiting areas, and recreational spaces.
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Research has demonstrated that CRC exhibits failure modes without disintegration, unlike traditional concrete. It offers good resistance to impacts and sound waves, making it suitable for use in structural elements in seismic areas to enhance ductility, as well as in highway construction for shock absorption and as protective barriers against explosions.
Published research:
Rubberised concrete properties and its structural engineering applications
Optimisation of rubberised concrete with high rubber content
Numerical study on dynamic properties of rubberised concrete with different rubber contents
Mechanical properties, durability and structural applications of rubber concrete: a state of the art review