Fiber reinforcement for floor foundations

The floor foundation is the layer between the elements that make up the flooring and the load-bearing element (floor). Thanks to industrial developments in the adhesives sector new floor-laying techniques have been developed: from the traditional technique of walling in the elements that make up the flooring we have moved on to gluing these elements to a specially prepared layer called floor foundation.

The floor foundation, which in its most sophisticated solutions can be made up of more than one sub-strata, has the following functions:
  • It incorporates and protects installations already present, particularly tubing.
  • It provides flattening and levelling of the rough sub-structure (floor).
  • It provides the floor below with soundproofing, reducing noise from footsteps on the floor above.
  • It provides thermal isolation of areas separated from each other horizontally.
  • Lastly, it allows the weight of loads on the flooring to be distributed more evenly before reaching the load-bearing structure (floor).
Problems encountered in laying floor foundations lie essentially in the hydraulic shrinkage of the cement mixture, which can cause crazing, lesions or even breaking away from the underlying structure. The creation of a good floor foundation using ordinary techniques requires the use of extremely high quality aggregates (rough and with very small quantities of fine parts), low doses of water and cement with the use of fluidifiers and floor foundation laying carried out with heavy trowel plastering by well qualified construction workers. Moreover, in hot weather conditions it is a good rule to limit the evaporation of water from the exposed surface, covering it with paper or plastic bags. This attention to detail, which is rather expensive, is often in contrast with the economical considerations of the building site.
In fact, the use of thick mixtures involve:
  • making pumping work, where needed, more difficult;
  • slowing down the task of pouring and laying;
  • employing qualified construction workers to create smooth and compact surfaces.
The problem of the breaking away of mortar and, more generally, of the mixes, can be controlled by special reinforcements. Steel fibers are an excellent solution to the problem in that, if they are laid uniformly and at casual intervals in the mixture, they bind the mixture while it is still fresh and provide it with resistance to stress during hardening, absorbing any stress that might cause crazing and lesions. Thanks to a high ratio between the side surfaces and volume, steel fiber sheets ensure good adherence to mortar and the absence of shaping at the edges does not pose a problem in the mixture phase. The ability of steel fibers to avoid the breaking away of mortar depends on correct doses. In fact the effect of the fiber reinforcement depends on the amount of fibers present in the mixture, which must be in sufficient number to be able to interact. The minimum quantity of fibers to be used should be fixed according to the geometric characteristics of the fibers and particularly according to the value of the ratio L/D (L=Length, D=Equivalent Diameter ).
The creation of floor foundations using mortar reinforced with steel fibers, using the correct amount of fiber reinforcement provides several advantages:
  • it avoids damage caused by hydraulic breaking away during hardening;
  • it increases the hold and resistance of the floor foundation layer;
  • it increases the flexible rigidity of the entire floor, because the floor foundation layer can interact with the resistant elements;
  • it improves weight distribution of loads on the flooring before reaching the load-bearing structure;
  • it improves surface resistance to abrasion, which allows movement on the floor foundation layer before the flooring is laid.
Where it is necessary to carry out reinforcement of the floor foundations, on account of high load-bearing requirements, fiber reinforcement with steel fibers is more practical and gives better results thanks to the absence of overlapping and is more economical compared with the use of panels with electro-welded net.