Using Steel Fiber Reinforced Concrete

Adding Fibers
Steel fibers should be added to the fluid mix in order to disperse them throughout the concrete mix and prevent them from clumping. This can be done in two ways. Steel fibers can be added to the transport mix truck after all other ingredients have been added and mixed. Steel fibers can be added along with fine aggregate in a plant set up to charge a central mixer or transport mixer.

How to Prevent Fiber Clumping
Fibers will usually clump before they are added to the concrete mix. If no clumps of fibers are added to the mix, the mix will almost always be free of clumps. Adding too much fiber to the mix or adding fiber too quickly to a rough mix can also cause clumps.

Do Not Add Water; Use a Vibrator
Although steel fiber reinforced concrete may appear stiff and difficult to work with, it can usually be poured quite easily after using a vibrator. Based on the appearance of the concrete and experience with conventional concrete, batching plant operators and truck drivers should not add additional water to the mix. The workability of fiber reinforced concrete poured by vibration is best measured using the inverted slump cone test method ASTM C 995. The time required for the inverted slump cone to be filled with fiber reinforced concrete after the vibrator is inserted into the concrete until the inverted slump cone is empty is called the inverted slump cone time. For steel fiber reinforced concrete, the inverted slump cone time should be between 10 and 30 seconds.