determination of the ten percent fines value
Determination of the Ten Percent Fines Value in Aggregate Production: A Critical Parameter for Quality Control
The aggregate industry plays a pivotal role in construction, providing essential materials for concrete, asphalt, and road bases. Among the key quality parameters for aggregates, the Ten Percent Fines Value (TFV) stands out as a critical measure of resistance to crushing under load. This value is particularly important for assessing the durability of aggregates used in high-stress applications, such as road pavements and heavy-duty foundations.
Understanding the Ten Percent Fines Value (TFV)
The TFV test determines the load required to produce 10% fines (particles smaller than 2.36mm) from a sample of coarse aggregate. A higher TFV indicates greater resistance to crushing, ensuring longer-lasting performance in structural applications. The test follows standards such as BS 812-111 or ASTM D5821, depending on regional requirements.
Key Steps in TFV Testing:
1. Sample Preparation – A dried aggregate sample (typically 14–20mm) is compacted in a steel cylinder.
2. Load Application – A compressive force is applied at a controlled rate until 10% fines are generated.
3. Calculation – The TFV is derived from the maximum load sustained before fines production.
Relevance to Crushing and Screening Equipment
The TFV directly influences the selection of crushing equipment:
- Jaw Crushers & Cone Crushers – Ideal for producing high-TFV aggregates due to their interparticle crushing mechanism.
- Impact Crushers – Suitable for softer rocks but may generate higher fines if not properly adjusted.
- Vertical Shaft Impactors (VSIs) – Used in manufactured sand production, where controlling fines is critical for concrete quality.
- Pre-crushing with jaw crushers for initial size reduction.
- Closed-circuit grinding to recirculate oversized particles.
- Moisture control to prevent fines agglomeration.
Optimizing crusher settings (e.g., CSS, rotor speed) and screening efficiency ensures minimal unwanted fines while maximizing TFV compliance.
FAQ on TFV in Aggregate Production
Q1: Why is TFV more critical than Aggregate Crushing Value (ACV)?
A: TFV measures resistance under higher stress, making it more relevant for heavy-load applications like highways.
Q2: How can producers improve TFV?
A: Selecting harder rock sources, optimizing crusher settings, and using multi-stage screening reduce excessive fines.
Q3: Does TFV apply to manufactured sand?
A: Yes, especially in concrete mixes where excess fines weaken compressive strength.
Case Study: High-TFV Aggregate for Highway Construction
A quarry in Scandinavia upgraded its crushing circuit by integrating a tertiary cone crusher with a precision screening system. This reduced fines by 15% and increased TFV by 20%, meeting stringent roadbase specifications. The solution emphasized:
Conclusion
The Ten Percent Fines Value remains a cornerstone of aggregate quality control, guiding equipment selection and process optimization. By prioritizing TFV compliance, producers ensure durable, high-performance materials for critical infrastructure projects. Continuous advancements in crushing technology further enhance the ability to meet evolving industry standards.