Hybrid reinforcement is gaining popularity 

Engineers and contractors are increasingly choosing traditional reinforcement combined with steel fiber reinforcement to better reinforce (parking) basements of apartment buildings and offices against water pressures. This way, in fact, they can do better crack control. These are a few striking evolutions they have observed at Bekaert in recent years.

In the past, steel fibers were mainly used for industrial floors. In recent years, Bekaert has seen steel fibers find their way into structural applications as well, such as foundation slabs and walls for underground car parks and cellars of apartment buildings. "The undersides of the foundation plates of parking garages and cellars of residential projects are subject to water pressure because they are built near and below the water level of a canal or river, for example. Thanks to steel fibers, crack control can be improved," says Ben Vanheuverzwijn, Business Development Manager at Bekaert. A few years ago, Bekaert was also involved in the construction of the new home of the National Museum of Norway, the country's largest cultural center with an area of 54,000 square meters. "That project is right by the sea and therefore also had to contend with high water pressures, up to 9 m. So here too we were able to convert the classic reinforcement to a hybrid reinforcement and added steel fibers. The deeper you build, the more the water pressure rises and the more important it is to do crack control. If the cracks get too big, the water just runs through, with all the consequences. Other recent examples are the Grotius projects in The Hague, Nieuw-Zuid in Antwerp and the IJboulevard at the central station in Amsterdam."

Crack Control 

To control cracking and achieve certain crack widths, contractors and engineering firms should opt for hybrid reinforcement, according to Vanheuverzwijn. "The tensile strength and end hook anchorage of the Dramix® 4D fibers were specifically developed to control cracking and limit crack gaps between 0.1 and 0.3 mm to create durable and fluid-tight structures. These fibers, which among other things have a SECO application certificate in Belgium, offer the highest fR1 value of all our fibers. They thus have the highest residual tensile strength just after the point of cracking according to a standardized beam test and offer the best post-crack strength at small crack openings. The steel fibers are homogeneously distributed throughout your concrete mass. With hybrid reinforcement, more cracks develop but those openings are much smaller and finer, thus providing a more efficient barrier against water seeping in. From the moment a small crack occurs in the concrete, it will immediately be bridged by another fiber. With traditional reinforcement, there are fewer cracks, but they are often much larger allowing water to pass through."

Popular 

Bekaert has noticed that engineers, engineering firms and contractors are increasingly opting for hybrid reinforcement combined with steel fibers. "We see that traditional reinforcement is being converted more and more to hybrid reinforcement, in combination with steel fibers. We find that many engineering firms have difficulty dealing with water pressure and everyone has their own calculation methodologies. Our company provides extensive technical support in determining the most appropriate fiber type, optimal dosage and concrete grade involved, for a wide range of applications. Once contractors have used our product, they also see the many advantages of it in terms of material cost, labor, placement, time and durability. Certainly the latter is becoming increasingly important, and to meet the demand for an 'embodied carbon' analysis, we also obtained our EPD document for our Dramix® steel fibers this year."