Reinforcement for industrial flooring

An apparently simple functional element likeflooring actually represents a rather complexengineering problem.From a structural point of view, a floor is a slab laidon top of a deformable foundation. In the design ofconcrete flooring, two distinct aspects must beconsidered:
  • Taking into account the rheological propertiesof the concrete, shrinkage in particular, it isnecessary first of all to tackle and solve theproblems associated with the transitory phase inwhich the cast concrete undergoes curing. Infact, coactive stresses may occur due toshrinkage; if they exceed the resistance of thematerial, they will manifest themselves throughcracking and undermine the monolithic natureof the structural element.
  • Subsequently the "flooring" element will haveto be endowed with adequate resistance basedon the useful life of the facility itself andplanned loads.
Various factors may cause stress in flooring; theyare generally classified as follows:
  • Static loads (in specific points or distributed inone direction or across surfaces);
  • Moving loads;
  • Thermal loads.

Each type of load induces specific stresses:concentrated loads (shelving, machinery, etc.)induce considerable compressive tangential stresses and two-dimensional bending stresses; loads distributed in one direction (usually walls) mainly induce bending stresses; moving loads, basically represented by vehicles in transit, induce bending stresses that vary over time and hence fatigue.Temperature changes cause strains and stresses corresponding to the degree of the changes themselves. The design of industrial flooring involves the identification of a solution capable of meeting the challenges of every working situation. In the specific case of concrete flooring, the traditional solution is to embed metal reinforcements in the concrete and, while the floor is being laid, to introduce functional joints. This kind of reinforcement, made up of electrically welded metal meshes arranged in one or two tiers, mainly lends flexural strength to the concrete. As regards surface strength and resistance to compression, reliance is made on the intrinsic strength of the concrete.  The improvements in the techniques for reinforcing concrete ­ and in particular the use of extensive steel fiber reinforcements ­ have allowed the structural problems of industrial flooring to be tackled and solved in a more successful manner. In fact, steel fibers modify the intrinsic properties of concrete: the ductility lent by the fiber reinforcement enhances both its flexural and fatigue strength, while the increased resistance to tangential stresses improves its compressive strength. Fiber-reinforced concrete is also endowed with great surface hardness. This characteristic is highly important in the presence of impacts or grazing loads caused by the maneuvers of motor vehicles. From an engineering standpoint, the choice of fiber reinforcement will depend on the Mix Design of the concrete itself and the amount of stresses induced by planned loads. From a practical viewpoint, designing the fiber reinforcement means defining the geometric characteristics of the fibers, their length (L) and equivalent diameter (D) in particular, and the proportions to be used.  These parameters, in particular the aspect ratio L/D and proportions, are closely correlated. The performance features of a fiber-reinforced composite may be rigorously assessed only through direct experimentation. In practice, it is thus possible, after introducing the appropriate safety coefficients, to correlate the flexural strength of fiber-reinforced composites with the characteristic compressive strength of concrete. The tables below show the flexural strengths of the types of fibers normally used in industrial flooring. These values may be used for the purpose of designing a fiber reinforcement.
The FIBROCEV technical service is at the disposal of designers, whom it may aid, backed by its own experience, in identifying the optimal fiber reinforcement according to the engineering problems to be solved.