A crushing plant can produce aggregate within the correct size range and still fail the client’s particle-shape requirement.
This usually happens because screening controls particle size, not particle shape. A thin or elongated stone may pass through the correct screen opening when it approaches at a favorable angle. It reaches the finished-product stockpile, but later fails a flakiness or elongation test.
The solution is not always to install another crusher.
Before changing equipment, determine which product fraction fails, where the poor shape first appears and whether the cause is the rock, the feeding condition, the crushing chamber, worn liners or the process arrangement.
In many plants, improving aggregate shape begins with correcting the existing operation. A separate impact crusher or VSI shaping stage should be evaluated only when those corrections are insufficient.
What Are Flaky and Elongated Aggregate Particles?
A flaky particle is thin relative to its other dimensions. An elongated particle is disproportionately long. The exact classification depends on the test method and limit specified for the project.
Excessive flaky and elongated particles may:
- Make aggregate more difficult to compact
- Increase breakage during handling or compaction
- Affect interlocking in unbound aggregate layers
- Increase paste demand for a given concrete workability
- Reduce the amount of finished aggregate that meets the client’s specification
However, cubical shape alone does not make an aggregate suitable.
Grading, strength, abrasion resistance, cleanliness and intended use must also meet the relevant specification. Particle shape is one quality indicator within the complete aggregate-production process.
Start by Identifying Where the Problem Appears
A frequent mistake is to change the crusher setting before establishing where the shape problem begins.
Representative samples should be collected from:
- The secondary crusher discharge
- The tertiary crusher or shaping-stage discharge
- The return material in a closed circuit
- Every finished aggregate size fraction
- Any bypass stream entering the final product
Equivalent size fractions should be compared using the same test method. Testing only one combined stockpile sample can hide a problem concentrated in a particular product.
For example, a plant producing nominal 5–10 mm and 10–20 mm aggregate should test those fractions separately. These sizes are illustrative rather than universal specifications.
The operating team should also record whether the change followed:
- A move to another quarry face
- A liner replacement
- Increasing liner wear
- A change in feed rate
- A new closed-side setting
- A change in screen media
- The addition of a bypass stream
This establishes a timeline. Without it, the plant may spend money correcting the wrong stage.
Six Common Causes of Flaky Aggregate
1. The rock breaks along layers or weak planes
Some rocks naturally split along bedding, foliation, weathered surfaces or existing fractures. They may produce flat fragments even when the crusher is mechanically sound.
Rock names are not enough to predict this behavior. Two deposits both described as granite, limestone or basalt may respond differently because their mineral composition, structure and degree of weathering differ.
If aggregate shape changes after moving to a new quarry face, examine representative feed samples before changing the equipment. Where practical, compare crushing trials from the old and new material zones under similar operating conditions.
2. The cone crusher is not receiving a stable feed
Cone crusher product shape depends partly on how material enters and fills the crushing chamber.
Intermittent feeding, an underfilled cavity or material concentrated on one side can produce unstable crushing conditions. The crusher may still operate, but product grading, liner wear and particle shape can fluctuate.
The plant should check:
- Surge-bin capacity
- Feeder control
- Feed-chute geometry
- Material segregation before the crusher
- Distribution around the crushing chamber
- Whether the recommended chamber level is maintained
Choke feeding means maintaining an appropriate material bed inside the chamber. It does not mean forcing excessive material into the crusher or operating beyond its approved load.
3. The crushing chamber does not match the actual duty
A chamber selected for coarse secondary crushing may not be suitable for a finer finishing duty.
Cavity selection should reflect the real feed grading, required reduction ratio and target product. Maximum feed size alone is not enough. The full feed distribution determines how the material occupies the chamber.
The closed-side setting, or CSS, also influences:
- Product grading
- Crusher capacity
- Circulating load
- Power demand
- The amount of fine material produced
Reducing CSS is therefore not an automatic solution to poor aggregate shape. It should be treated as a controlled process adjustment and evaluated through representative sampling.
4. Worn liners have changed the crushing conditions
A control system may display the same crusher setting while the effective crushing profile has changed because the mantle and concave are worn.
Uneven liner wear can alter material movement through the chamber, reduce effective interparticle crushing and create inconsistent product.
Operators should monitor more than the number of operating hours. Liner profiles, actual discharge opening, power draw, product grading and shape results should be reviewed together.
If shape deteriorates gradually during the liner cycle, the plant should determine whether the chamber selection, feed distribution or replacement schedule needs adjustment.
5. One crushing stage is being asked to do too much
A plant may expect one crusher to accept a broad, coarse feed and produce a small finished aggregate in a single stage.
This makes it difficult to balance throughput, wear, product grading and particle shape. Repeatedly tightening the final crusher may reduce capacity or create excessive fines without solving the underlying problem.
The better approach is to review how reduction is divided across the complete line:
Feeding → Primary crushing → Secondary crushing → Tertiary crushing or shaping → Screening
Improving upstream feed preparation or adding an appropriate finishing stage may be more effective than forcing an unsuitable reduction ratio through one machine.
The required number of crushing stages depends on the material, feed size, target capacity and finished-product specification.
6. Poorly shaped material is bypassing the finishing stage
Even when the crusher discharge is acceptable, finished stockpiles may fail because of incorrect material routing.
Possible causes include:
- An unshaped bypass stream entering the product
- Return material being directed to the wrong stage
- Product fractions mixing at transfer points
- Stockpile contamination
- Flat particles passing the screen in a favorable orientation
Closed-circuit crushing helps control top size and returns oversize material for further processing. It does not guarantee acceptable particle shape by itself. Finished aggregate must still be sampled and tested.
Can a Cone Crusher Produce Cubical Aggregate?
Yes. A correctly selected and properly operated cone crusher can produce acceptable aggregate shape, including when processing hard and abrasive rock.
Before purchasing an additional shaping machine, check:
- Whether the feed is stable
- Whether material is distributed evenly
- Whether the cavity suits the feed grading
- Whether the CSS is appropriate
- Whether the mantle and concave are worn
- Whether the crusher is working within its intended reduction duty
- Whether the screen and return circuit are correctly arranged
After making corrections, allow operating conditions to stabilize and test every affected finished fraction again.
If the aggregate then meets the project requirement, an additional shaping stage may be unnecessary.
When Should an Impact Crusher Be Considered?
A horizontal-shaft impact crusher breaks material through rotor-mounted blow bars and impact surfaces. It can combine size reduction with particle-shape improvement and often produces a relatively cubical product.
It is worth evaluating for suitable low-abrasion material, including some limestone applications.
However, equipment selection should not be based on the rock name alone. Quartz content, abrasiveness, feed size and required reduction duty influence blow-bar wear and operating cost.
For highly abrasive feed, improved product shape may be offset by rapid wear and a higher cost per saleable tonne.
The decision should therefore consider both product quality and the actual material characteristics.
When Does VSI Aggregate Shaping Make Sense?
A VSI crusher is worth evaluating when the existing crushing circuit already achieves the required size but cannot consistently meet the particle-shape specification.
Depending on its configuration, a VSI crusher uses rock-on-rock or rock-on-anvil impact. Its performance is influenced by:
- Feed-size distribution
- Maximum permitted feed size
- Material abrasiveness
- Rotor and wear-part condition
- Operating speed
- Feed rate
- The required balance between coarse aggregate and manufactured sand
Increasing rotor speed may intensify shaping, but it can also increase wear, produce more fines and alter throughput. Any change should remain within the equipment manufacturer’s approved operating range.
For coarse aggregate production, it may be unnecessary to send the complete plant output through the VSI.
If only one finished fraction fails the shape test, the plant can evaluate routing that fraction through the shaping stage and then rescreening the discharge. This avoids reprocessing material that already meets the specification.
Better Shape Does Not Always Mean Better Economics
Breaking a flaky particle may create a more cubical particle, several smaller fragments or a combination of both.
A lower flakiness result can therefore be accompanied by:
- Higher fine-material production
- Lower coarse-aggregate yield
- Increased power consumption
- Additional wear costs
- Higher circulating load
- Reduced throughput
The real production target should be tonnes per hour of compliant, saleable aggregate—not simply tonnes passing through the crusher.
Before and after every adjustment, compare:
- Shape results for each finished fraction
- Saleable output of each specification
- Changes in grading
- Fine-material generation
- Crusher power consumption
- Wear cost per saleable tonne
- Return load
- Screen performance
- Overall plant throughput
Adjust one variable at a time. Allow the circuit to stabilize before sampling, and keep the material source and test method as consistent as possible.
This makes it easier to identify which change produced the result.
A Practical Troubleshooting Sequence
When flaky aggregate appears, the following order usually provides a more disciplined investigation:
Step 1: Confirm the requirement
Identify the specified test method, permitted limit and affected finished-product size.
Step 2: Sample the process
Collect representative material from crusher discharges, return streams and finished stockpiles.
Step 3: Check material variability
Determine whether the problem began after moving to a different quarry face or processing a weathered material zone.
Step 4: Inspect cone crusher operation
Review feeding stability, distribution, cavity level, chamber selection, CSS and liner condition.
Step 5: Review the complete circuit
Check bypass streams, screen performance, recirculating load and product mixing.
Step 6: Conduct controlled trials
Change one operating variable at a time and compare compliant product output rather than crusher throughput alone.
Step 7: Evaluate another crushing or shaping stage
If operational corrections cannot meet the specification, compare impact crushing and VSI shaping against material abrasiveness, wear cost, fines production and saleable yield.
How Leimeng Group Approaches Aggregate Shape Improvement
Leimeng Group provides cone crushers, impact crushers, VSI sand-making and shaping equipment, vibrating screens, feeders and complete aggregate crushing plant solutions.
For a plant experiencing excessive flaky and elongated aggregate particles, equipment selection should begin with the existing process rather than a predetermined machine.
The assessment may indicate a need to:
- Stabilize the cone crusher feed
- Change the crushing chamber
- Correct the CSS
- Replace or review worn liners
- Modify the closed-circuit crushing arrangement
- Evaluate an impact crusher for suitable material
- Add VSI aggregate shaping for selected fractions
- Improve final screening and material routing
To assess a project, the useful starting information includes:
- Raw material and project location
- Required plant capacity
- Current crusher models
- Process flow and feed sizes
- Finished-product specifications
- Intended aggregate application
- Shape-test method and recent results
- Photos of the feed and finished aggregate
These details help determine whether the problem can be corrected through operation, circuit modification or an additional shaping stage.
Frequently Asked Questions
Why is my aggregate flaky even though the size is correct?
Screening separates material mainly by size. A thin or elongated particle can pass through an opening in a favorable orientation and still fail a particle-shape test.
Does reducing the cone crusher CSS always improve aggregate shape?
No. CSS affects grading, capacity, load and circulating material, but it is not a universal cure for poor shape. Its effect must be verified through controlled testing.
Is choke feeding always required for a cone crusher?
A cone crusher generally benefits from stable feeding and an appropriate material level, but the correct operating condition depends on the machine and chamber. Choke feeding should not be confused with overloading.
Is a VSI crusher only used for manufactured sand?
No. VSI crushers can also be used to shape suitably sized coarse aggregate. The result depends on feed size, machine configuration and operating conditions.
Should the complete aggregate output pass through the VSI?
Not necessarily. If only one fraction fails, selective shaping may preserve more compliant coarse product and avoid unnecessary processing.
What is an acceptable flakiness level?
Use the test method and limit specified by the project or local market. There is no single percentage suitable for every aggregate application.
Conclusion
Flaky aggregate is rarely solved by changing one setting without first understanding the complete process.
The problem may begin with the rock, unstable cone crusher feeding, an unsuitable chamber, worn liners, excessive reduction in one stage or incorrectly routed material. A separate impact crusher or VSI shaping machine can be effective, but only when it addresses a clearly identified limitation.
The most useful measure of success is not a better-looking stockpile or a higher crusher throughput. It is the stable production of correctly graded, specification-compliant aggregate at an acceptable cost per tonne.
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GUANGDONG LEIMENG INTELLIGENT EQUIPMENT GROUP CO.,LTD.