Issue link: https://geospatial.trimble.com/en/resources/i/1415420
august 2019 csengineermag.com 59 In fact, fiber reinforced concrete is not new. Many companies supply fibers for use in concrete with the objective of improving strength and durability of concrete in some way. Fiber reinforced concrete accomplishes this by incorporating fibers made of steel, glass or organic polymers (plastics). Sometimes naturally occurring fibers such as sisal and jute have been used as well. These fibers are primarily used to combat plastic shrinkage and drying shrinkage which can otherwise crack and damage the concrete. This resistance to shrinkage and subsequent cracking is the key to extending the lifespan of concrete, decreasing the frequency of costly repairs. Fibers also keep existing cracks from widening and further damaging the concrete when they do ap- pear. And more recently, steel fibers are being used in structural applications to reduce the amount of traditional steel reinforcing bars, saving time and labor. Case Study: 42 Broad, Fleetwood, New York 42 Broad is a 16-story mixed-use development near New York City being built with Insulating Concrete Forms (ICF). ICF construc- tion is becoming more mainstream with thousands of projects built in the US, but still considered innovative by many. ICFs sandwich a reinforced concrete wall between forms made of rigid polystyrene insulation that stay in place after the concrete hardens. There are several taller ICF buildings in Canada, but at 16 stories, 42 Broad will be the tallest in the US. The real innovation on this project is panelizing the Amvic ICF blocks and using Helix TM steel fiber reinforcement. The ICFs are assembled off-site in a nearby plant and arrive at the jobsite as custom panels up to 50 feet long which results in labor and time savings on the job site, meaning the owner can occupy the building earlier. Part of what makes this process possible is the use of steel fibers in the ready mixed concrete to replace the horizontal reinforcing steel which eliminates costly horizontal rebar slices. LafargeHolcim is one of the first companies to commercialize bendable concrete with a product called Ductal®. Ductal® is an ultra-high-performance concrete (UHPC) that incorporates fibers into the concrete mixture in order to improve strength and ductility along with a host of other benefits. LafargeHolcim distributes the premix powder, fibers and admixtures necessary to produce Ductal® to their partners, who then mix it into concrete. LafargeHolcim states that they use "high carbon metallic fibers, stainless fibers, poly-vinyl alcohol (PVA) fibers or glass fibers" to increase the concrete's ability to withstand tensile loads and deformation. Ductal® is also less porous than conventional concrete, making it more resistant to chlorides, acids, and sulfates. It is also gener- ally much more impermeable to water, making it ideal for roofing as well. In addition, Ductal® has self-healing properties. This bendable concrete has been thoroughly researched and is commercialized. Read more here Photo: Bluestone Organization Photo: ICF Panels, Inc.