Over the years, research and development in the field of fiber-reinforced concrete have led to the introduction of various types of fibers, improved concrete mix designs, a better understanding of fiber-matrix interactions, and shedding light on the debate of micro fibers vs. macro fibers for certain applications. The ongoing exploration of new fibers, their sizes, and innovative concrete composites continues to advance the field and expand the potential applications of fiber-reinforced concrete in modern construction and infrastructure projects. This article will examine the beneficial properties of concrete micro fibers vs. macro fibers and how to make the right choice for your specific application.
What Are Concrete Microfibers?
Concrete micro fibers can be classified as any fiber with a length between 6 and 18 mm and can be other two variants: monofilament or fibrillated. Due to their “micro” size, this class of concrete fibers is an ideal additive for shrinkage control measures that typically occur within the first 24 hours of the concrete curing process. They can also significantly boost impact protection and even the reduction of spalling in the event of a fire. Micro fibers can be used instead of light welded wire fibers, offering added performance benefits while decreasing cost and weight.
Shotcrete, sprayed at high velocity onto a surface rather than poured, enhanced with concrete micro fibers has shown incredible results in improving the durability of the concrete to withstand continual freeze-thaw cycles. It also provides added resistance to both impact and abrasion, helping to avoid cracks and fractures that allow for moisture to penetrate beneath the top layer. Micro fibers are the more versatile option when compared to macro fibers and offer premium performance benefits at an affordable cost, even for large structures.
What Are Concrete Macro Fibers?
Concrete macro fibers are typically between 38 and 52 mm in length and provide a greater range of protection than micro fibers. Due to this, macro fibers are more commonly used in large infrastructure projects like bridges or building foundations where the longer strands provide better protection against post-cracking beyond the initial 28-day benchmark. Like micro fibers, macro fibers significantly improve the freeze and thaw and provide considerable protection against shrinking throughout the curing process. Macro fibers are predominantly used to maintain the integrity of the concrete post-cracking and ensure that any cracks that do occur during curing do not continue to expand. Macro fibers can help with plastic shrinkage cracking in the first 24 to 48 after pouring and also serve as a secondary reinforcement that can replace certain gauges of rebar in certain applications.
Macro fibers can be added to several different methods of concrete application without any concerns about their dispersal throughout the mixture. This includes both traditional concrete pours and high-velocity shotcrete methods used to create the strong walls lining underground transportation methods. When used in shotcrete applications, macro fibers provide increased levels of adhesion on the first pass, so operators can apply thicker layers without having to worry about wasted fall-off.
Micro Fiber vs. Macro Fiber - How to Make the Right Choice?
Making the right decision of concrete micro fiber versus macro fiber comes down to the application and specific performance improvements required to provide optimal results. In some instances, as you’ll see below, both fiber sizes offer similar levels of enhancement to the concrete. If you have any questions about which size fiber is the best choice for your application, please reach out to our experienced team and we would be happy to guide you through the decision process.
Reduce Early-Age Cracking: Micro fibers are an ideal SCM to provide incredible protection from cracking early in the curing process, typically within the first 24 hours. Early-age cracks can completely derail any concrete application and should be avoided at all costs.
Protection From Applied Forces: Large concrete structures that will experience heavy loads and applied forces should be reinforced with macro fibers. The larger diameter and longer strand lengths within the internal concrete matrix help to prevent this shrinkage cracking during the earliest stages of the curing process.
Spalling Resistance: Spalling refers to the degradation of the concrete surface in the form of cracks, chips, and peeling. While both can help prevent spalling, microfibers are the more frequently recommended option. Spalling is typically the result of the freeze and thaw cycle, alkali-silica reaction, and even instances of fire.
Reduced Shotcrete Rebound: Micro fibers are the more suitable version to help reduce the rebound rate in shotcrete applications. Rebound refers to excess concrete falling away from the intended surface, ultimately adding both cost and time to the project. Thoroughly mixing microfibers into the concrete allows operators to apply thicker layers in a single pass and minimize rebound.
Ask The Experts at R-E-D About Micro Fiber vs. Macro Fibers
At R-E-D Industrial Products we pride ourselves on our industry knowledge and will work closely with you to understand your project requirements and provide insight into which concrete fiber is best suited for your application. With a comprehensive catalog of supplementary cementitious materials, we’ve worked with countless industries to optimize the performance and durability of concrete. When you reach out to us with details about your upcoming project, our team can quickly weigh the benefits of microfibers versus macro fibers and provide you with an immediate quote with competitive pricing and fast delivery times. We look forward to hearing from you and delivering premium concrete fibers to processing facilities and job sites across the country.
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