| 1. |
Can steel fibers be added at the ready mix plant ? |
| 2. |
Can steel fibers be added on site ? |
| 3. |
Do I still need dowels at construction joints when using steel fibers ? |
| 4. |
Can steel fiber reinforced concrete be pumped ? |
| 5. |
Will steel fibers protrude from the surface ? |
| 6. |
Will steel fibers rust? |
| 7. |
Are steel fibers compatible with curing compounds ? |
| 8. |
Can abrasion resistant toppings and liquid sealants can be applied over steel fiber reinforced floors? |
| 9. |
Will steel fibers damage my power trowel? |
| 10. |
How do I cut joints on my steel fiber reinforced concrete slab? |
| 11. |
How will steel fibers affect my flatness and levelness ratings? |
| 12. |
How will steel fibers affect my concrete mix design? |
| 13. |
How can I quantify the differences between various steel fibers? |
| 14. |
What is meant by residual strength? |
| 15. |
How do I specify steel fibers? |
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| 1. |
Can steel fibers be added at the ready mix plant ? |
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Yes , introduce steel fibers after all other ingredients are already in truck. Set the truck mixer on charging speed and add fibers at a rate not to exceed 100 pounds/minute. Mix for a minimum of 40 revolutions at charging speed . |
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| 2. |
Can steel fibers be added on site ? |
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Yes, gradually feed fibers in the mix via conveyor or OHSA approved scaffolding . |
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| 3. |
Do I still need dowels at construction joints when using steel fibers ? |
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Yes, dowels are required at construction joints. Dowels at contraction joints are typically not required, due to aggregate interlock and steel fibers bridging the joint. Dowels may be required at contraction joints if spacing exceeds industry standards. |
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| 4. |
Can steel fiber reinforced concrete be pumped ? |
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Yes, but expect a 1 to 3 inch slump loss through the hose depending on the steel fiber dose rate, ambient temperatures and hose length. A mid-range water reducing agent (MRWR) is commonly used to enchance workability and ease of flow through pump lines. High-range water reducers (HRWR) may be required in some cases. Typically, a 4 to in. Diameter hose is required. |
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| 5. |
Will steel fibers protrude from the surface ? |
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No, use of vibratory or laser screeds in conjunction with highway straight edges and power float finishers typically causes to fibers to lay flat . |
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| 6. |
Will steel fibers rust? |
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Outdoor Applications With Cracks-Laboratory and field-testing of cracked SFRC in environments containing chlorides has indicated that the cracks in concrete can lead to corrosion of the fibers passing across the crack. However, hairline cracks (crack widths < 0.004-in.) do not allow corrosion of steel fibers passing across the crack. If cracks wider than 0.004-in. are limited in depth, the consequences of this localized corrosion are not structurally significant. |
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| 7. |
Are steel fibers compatible with curing compounds ? |
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Yes, common curing compounds produed by a host of major manufacturers including Master Builders, Grace, and Euclid are commonly used on SFRC floors. |
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| 8. |
Can abrasion resistant toppings and liquid sealants can be applied over steel fiber reinforced floors? |
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Yes, steel fibers are compatible with dry shake or spray-on toppings. |
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| 9. |
Will steel fibers damage my power trowel? |
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No, power blade trowels and disc floaters are commonly used to provide a flat and level surface without excessive wear to the blades . |
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| 10. |
How do I cut joints on my steel fiber reinforced concrete slab? |
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Both wet-cut and early entry saws are commonly used to form contraction joints. Cut the joints to 1/3 slab depth, if possible, per ACI 302.1R guidelines. Generally limit joint spacing to ACI and PCA recommendations for unreinforced concrete. |
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| 11. |
How will steel fibers affect my flatness and levelness ratings? |
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Flatness and levelness are generally not affected at dosages up to 70 pounds per cubic yards. |
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| 12. |
How will steel fibers affect my concrete mix design? |
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Steel fiber mix designs are similar to those commonly used for plain concrete mixes. Recommended aggregate gradations and mix proportions are provided in ACI 544. Using the largest practical top size aggregate and a well-graded combined aggregate blend as opposed to a gap-graded blend can minimize shrinkage. Steel fibers may cause a reduction in slump due to their stiffness. This does not necessarily equal a reduction in workability. Depending on ambient temperatures and wether laser screeds are used, mid-range water reducers are commonly used to enchange workability for mixes with more than 30 to 40 pounds per cubic yards of steel fibers. The use of laser screeds facilitates steel fiber placement with slumps as low as 4 inches. |
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| 13. |
How can I quantify the differences between various steel fibers? |
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The residual strength factor (see below) is the most common factor used to differentiate steel fiber types. Steel fiber performance is a function of tensile strength, aspect ratio and anchorage. |
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| 14. |
What is meant by residual strength? |
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Residual strength values, or R-values, describe the level of flexural load capability as a percentage of the ultimate load of the unreinforced concrete. For example, concrete having a flexural strength of 700 psi might have a residual strength equal to 70 (R10,50=70). This means that the steel fiber reinforced concrete has a residual strength equal to 490 psi which is 70% of 700 psi. |
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| 15. |
How do I specify steel fibers? |
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Material specification- Steel fibers shall meet the requirements of ASTM A 820, except that the tensile strength shall be not less than _____psi. Steel fibers shall be Type______ (I,II,III,IV or V), Deformed length shall be ____MM. Diameter shall be ____mm. Certification and mill test reports shall be furnished for each shipment. |
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