Glued steel fibres may remain in bundles when the adhesive does not break down as intended, or when the concrete mix and mixing process do not provide enough moisture, movement, or time for separation. Common contributors include adding fibres too quickly, overloading the mixer, unsuitable workability, and a fibre type or dosage that does not suit the mix. A bundle does not automatically mean the fibres are defective: the cause can be material-related, process-related, or a combination. We recommend checking the fibre condition, batching sequence, mixer operation, and fresh-concrete consistency before changing the specified fibre dosage.
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Glued steel fibres are grouped with a water-sensitive adhesive so they can be handled and fed into concrete more consistently than a loose mass of individual fibres. During mixing, contact with water and the mechanical action of the mixer help the adhesive release and the fibres separate. The exact response depends on the adhesive system, fibre dimensions, concrete composition, and mixing conditions. Product-specific guidance should therefore take priority over a general rule.
Once separated, fibres need to distribute through the concrete without forming persistent clusters or obstructing placement. The challenge is not simply to increase mixing intensity: more mixing can affect workability and production time, while insufficient mixing may leave bundles intact. The practical objective is a repeatable sequence that disperses fibres while keeping the concrete suitable for its intended placement and finish.
Dumping a large quantity of glued fibres into one spot can create a concentrated mass that is difficult for the mixer to break apart. If fibres are introduced before the batch has enough circulating concrete, they may collect together rather than disperse. The appropriate addition point depends on the mixer, batch size, and mix design, so confirm the sequence with the concrete producer and fibre supplier.
The mixer must have enough time and effective movement to distribute the fibres through the batch. A heavily loaded mixer, unsuitable mixing speed, or worn mixing components may reduce circulation and leave poorly mixed zones. Simply extending mixing time is not always the answer; first check that the mixer is operating correctly and that the batch size is within its intended capacity.
Very stiff or cohesive concrete can make fibre incorporation harder, particularly when the mix has limited movement around the bundles. Aggregate grading, paste volume, admixture compatibility, and the specified water content can all influence fresh-concrete behavior. Do not add water as an informal remedy: any adjustment should comply with the approved mix design and project requirements.
Fibre length, diameter, aspect ratio, bundle size, and dosage can affect how fibres feed and disperse. For example, a longer fibre may need a different feeding and mixing approach from a shorter one, especially in a dense mix. Fibre dimensions and dosage should be selected for the engineering and placement requirements, not changed solely to make mixing easier without review.
Moisture exposure, damaged packaging, contamination, or prolonged storage in unsuitable conditions may affect the condition of the adhesive or the ability to feed bundles consistently. Check whether fibres are dry, free-flowing, and consistent with the supplied product information. If bundles appear unusually sticky, damaged, or inconsistent, document the condition and contact the supplier before using them in production.
Start by recording where bundles appear: during feeding, in the mixer, in a fresh-concrete sample, or during placement. Note the batch size, fibre dosage, addition sequence, mixing time, mixer type, and concrete consistency. This record helps distinguish a feeding problem from incomplete separation inside the concrete.
Next, inspect an appropriately collected sample using the project’s normal quality-control procedures. Look for intact glued bundles, uneven fibre distribution, and signs that fibres have collected in specific areas. Compare observations across batches rather than drawing a conclusion from one isolated sample, and follow site safety procedures when handling fresh concrete or samples.
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Where production allows, run a controlled trial with one change at a time. For example, as an illustrative trial—not a universal specification—a team might spread fibre addition over 30–60 seconds, then assess whether distribution improves under the same mix and mixer conditions. Another illustrative comparison is to evaluate 3–5 minutes of mixing after fibre addition, but the suitable duration must be confirmed for the actual equipment, batch, and product.
Feed fibres steadily rather than releasing them as a single compact mass, and avoid placing the entire quantity in one location if the equipment allows controlled distribution. Keep the batch size, sequence, and operating conditions consistent during trials. If the mixer is near its capacity, consult the plant or equipment guidance before attempting to compensate with longer mixing.
Check the approved mix design, aggregate moisture corrections, admixture use, and fresh-concrete consistency. If the concrete is unusually stiff or cohesive, involve the mix designer to determine whether a permitted adjustment is appropriate. Uncontrolled water addition can alter concrete properties and may create compliance or performance concerns.
Confirm that the fibre product, dimensions, packaging, and specified dosage match the project documents. Ask for the supplier’s recommended feeding sequence and mixing guidance for the actual fibre type. If the product has changed between deliveries, compare labels and product documentation rather than assuming that all glued steel fibres behave identically.
Not every visible group of fibres indicates the same failure mechanism. Some bundles may need additional mixing to separate, while other clusters may result from poor feeding, local congestion, or a mix that is unsuitable for the selected fibre geometry. Avoid diagnosing the issue from appearance alone when the concrete’s placement or performance is at stake.
Common mistakes include increasing water without approval, increasing the fibre dosage to compensate for poor distribution, changing several mixing variables at once, or continuing production without documenting the problem. Each action can make the cause harder to identify. If bundles persist after a controlled process review, pause and seek advice from the concrete producer, project engineer, and fibre supplier.
For procurement and project planning, ask the supplier to confirm fibre dimensions, packaging condition, product identification, and available technical handling guidance. Share the mixer type, batch size, concrete mix characteristics, target dosage, and observed symptoms when requesting support. This information makes a technical discussion more useful than a general request to “improve dispersion.”
At BEKA, we can discuss steel fibre product options and review the handling and application information relevant to a buyer’s requirements. The final fibre selection and mixing procedure should be validated with the project’s concrete producer and engineering team. Clear specifications and consistent supply documentation also help buyers investigate whether a problem is linked to a process change or a product change.
Glued steel fibres sometimes fail to disperse fully because the adhesive, mixing process, concrete consistency, fibre characteristics, or handling conditions are not working together. The best next step is to document the symptoms, verify the product and mixer conditions, and test controlled process adjustments without changing approved mix requirements. Use supplier guidance for the specific fibre rather than relying on a universal mixing time or dosage recommendation.
If your team is sourcing steel fibres or troubleshooting persistent bundles, share the product specification and mixing conditions with BEKA. We can help review the relevant product and handling questions so your team can coordinate an informed next step with its concrete producer and project engineer.
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