Concrete Fibers

Known as temperature and shrinkage reinforcing, macro synthetic fibers are used to control contraction joints or saw cuts and random crack widths, should they occur, due to thermal changes. Unlike rebar and welded wire mesh, fibers provide three-dimensional reinforcement so that when a crack forms, ideally in a control joint, there are numerous fibers bridging the joint, thereby minimizing the width and length of the crack. In addition, fibers increase the toughness of the concrete, which aids in limiting deterioration due to impact, abrasion, and fatigue.

Do fibers prevent cracking?

Concrete is designed to crack which is why joints are installed in pavements and interior slabs at regular intervals. Fibers are used to minimize the joint widths, thereby maintaining aggregate interlock which provides load transfer at the joint. Random cracks can happen and their occurrence can be greatly minimized by following guidelines established by the American Concrete Institute (ACI) for concrete slab installation which includes:

• Proper subgrade preparation
• Mixture selection
• Installation practices, including control joint installation and by properly curing the concrete after final finishing.

The American Concrete Institute (ACI) recognizes the use of macro-synthetic fibers as a suitable replacement for reinforcing bars (rebar) and welded wire mesh (WWM) when used to control drying shrinkage cracking and thermal changes (ACI 544.4R). Fiber reinforced concrete has many benefits, including but not limited to:

• Faster construction times through reduced labor
• Lower construction costs
• Safer project site
• Elimination of welded-wire mesh and conventional reinforcing bars used for temperature and shrinkage reinforcement
• Reduced plastic shrinkage cracks when using micro fibers
• Increase in toughness, abrasion and impact resistance
• Critical element of Latitude, Cemstone’s Extended Joint Spacing System