Bauxite is a natural mineral with aluminum oxide (Al₂O₃) as the main component, usually containing impurities such as iron, silicon, and titanium. In recent years, its unique physical and chemical properties have gradually attracted attention in paving projects, especially in the field of anti-skid pavement. The following is the specific application and technical analysis of bauxite in anti-skid pavement projects:
1. Characteristics of bauxite and its compatibility with anti-skid pavement
High hardness and wear resistance:
Bauxite has a high aluminum oxide content (70%~90%) and a Mohs hardness of 7~8, which is significantly higher than ordinary limestone (3~4). It can enhance the wear resistance of the pavement and extend its service life.
Rough surface structure:
Bauxite particles are mostly porous or angular. After paving, they can form microscopic concave-convex textures, increase the friction coefficient of the pavement (up to 0.7~0.8 under dry conditions and 0.4~0.5 under wet conditions), and effectively prevent slipping.
High temperature resistance and chemical stability:
Alumina has a high melting point (2050℃) and can withstand high temperatures (160~180℃) during asphalt paving. It is also resistant to acid and alkali corrosion and is suitable for complex environments (such as roads around chemical plants).
Environmental compatibility:
Bauxite is a natural mineral that does not release volatile organic compounds (VOCs), which meets the needs of green road construction.
2. Specific application forms of bauxite in anti-skid pavement
(1) As an aggregate to replace traditional stone
Incorporation of coarse aggregate:
Crushed bauxite particles (particle size 4.75~19mm) are used to replace part of basalt or granite aggregates (10%~30%) in asphalt mixtures (such as SMA-13, OGFC-16) to improve surface roughness.
Modification of fine aggregate:
Bauxite powder (<0.075mm) is used as a filler to replace limestone powder to improve the adhesion of asphalt mortar and reduce water damage.
(2) Anti-skid coating materials
High-aluminum-based anti-skid coatings:
Calcinated bauxite (Al₂O₃>85%) is mixed with epoxy resin, polyurethane and other binders to form a spray-type anti-skid coating, which is suitable for key areas such as bridge decks and ramps, and the friction coefficient can reach BPN (swing value) above 75.
Cold-laid thin layer technology:
Bauxite aggregate (particle size 2~5mm) is combined with modified emulsified asphalt to form a 1~3mm thick anti-skid layer, which is easy to construct and quick to open to traffic.
(3) Permeable pavement enhancement
Permeable concrete additives:
The porous properties of bauxite can increase the porosity of permeable concrete (up to 20%~30%), while reducing the wear and collapse of permeable pavements through high-hardness aggregates.
3. Comparison of the advantages of bauxite anti-skid pavement
Indicators Bauxite anti-skid pavement Traditional basalt anti-skid pavement Resin-based anti-skid pavement
Friction coefficient (BPN) 70~80 60~70 80~90
Abrasion resistance (wear value, %) ≤12 (Los Angeles method) ≤15 ≤5 (but high cost)
Cost (yuan/㎡) 80~120 60~100 200~300
Construction convenience Compatible with conventional paving equipment Applicable to conventional equipment Requires special spraying equipment
Environmental adaptability High temperature resistance, freeze-thaw resistance Easy to freeze-thaw peeling Chemical corrosion resistance
4. Key technical points
Aggregate processing technology:
Bauxite needs to be crushed, screened, and pickled (to remove iron impurities) before use to ensure that the gradation meets the “Technical Specifications for Highway Asphalt Pavement Construction” (JTG F40).
Asphalt mixture optimization:
Use high viscosity modified asphalt (such as SBS modification), and the amount of bauxite should not exceed 30% to avoid excessive viscosity of the mixture affecting paving.
Anti-stripping agent addition:
Add 1%~2% of amine anti-stripping agent (such as ASP-2) to enhance the adhesion between bauxite and asphalt and reduce the risk of water damage.
5. Practical application cases
Case 1: A toll plaza on a highway in China uses bauxite-SMA pavement (25% admixture), the friction coefficient is increased by 18%, and no obvious rutting occurs within 3 years.
Case 2: A bicycle lane in a Nordic city uses a bauxite-based cold-laid anti-skid thin layer, and the braking distance on ice in winter is shortened by 30%.
6. Challenges and future directions
Impurity control: Low-grade bauxite needs to be purified by flotation and magnetic separation, which increases costs.
Standardization promotion: There is a lack of special specifications for bauxite pavements, and a long-term performance database needs to be established.
Composite technology: Compound with steel slag, rubber particles and other materials to develop multifunctional anti-skid pavement (such as noise reduction + anti-skid).
Conclusion
Bauxite has become a competitive material in anti-skid pavement engineering due to its high hardness, rough surface and environmental protection characteristics. By replacing traditional aggregates or preparing special coatings, the safety and durability of the pavement can be significantly improved. In the future, it is necessary to further optimize the processing technology, reduce costs, and promote its large-scale application in urban roads, bridges, airports and other scenarios.
