bs 812 aggregate impact value
Understanding BS 812 Aggregate Impact Value in the Context of Crushing and Sand-Making Equipment
The construction and mining industries rely heavily on high-quality aggregates, where the BS 812 Aggregate Impact Value (AIV) serves as a critical metric for evaluating the toughness and resistance of aggregates to sudden impact. This standard is particularly relevant for manufacturers and operators of crushing and sand-making equipment, as it directly influences material selection, equipment design, and operational efficiency.
Industry Background
Aggregates must withstand dynamic loads during construction applications, such as road bases or concrete mixes. The BS 812 AIV test measures an aggregate’s ability to resist fragmentation under impact forces, simulating real-world conditions like transportation or compaction. A lower AIV indicates stronger, more durable material—essential for long-lasting infrastructure.
Equipment Implications
1. Crusher Selection: High-AIV aggregates (brittle materials) may require secondary/tertiary crushers (e.g., cone crushers) to reduce over-breakage, whereas low-AIV materials (e.g., granite) can tolerate primary jaw crushers.
2. Sand-Making Optimization: Vertical shaft impactors (VSIs) are ideal for producing cubical aggregates from low-AIV rocks, ensuring better particle shape for concrete mixes.
3. Wear Resistance: Aggregates with high AIV often contain abrasive minerals, necessitating wear-resistant liners in crushers and screens.
FAQ
Q: How does AIV affect aggregate pricing?
A: Low-AIV aggregates command premium prices due to their durability, but crushing costs may rise for harder rocks.
Q: Can AIV be improved through processing?
A: No—AIV is inherent to the rock type, but proper crushing stages (e.g., multi-stage reduction) can minimize unwanted fines.
Case Study
A quarry in Scotland switched from a single-stage hammer crusher to a three-stage circuit (jaw + cone + VSI) for basalt (AIV=18%). This reduced fines by 22% and improved product shape, meeting BS 812 specs for highway projects.
Conclusion
Understanding BS 812 AIV helps optimize crushing/sand-making processes, balancing quality and operational costs. Equipment choices must align with aggregate characteristics to ensure efficiency and end-product compliance.