Here's an explanation of the Three Keys to Properly Applying a Compression Layer In a floor slab: Mixing, pouring, and curing.
The compression layer, which can sometimes be found in bibliographies as “sheet metal”, is the concrete layer which spans the joists and hollow blocks of a floor slab and serves to transfer the vertical loads from the bathroom to the joists, and subsequently to the columns and the floor. It is a cast-in-place concrete structural element, It is typically used on-site and must be reinforced on the inside with electro-welded mesh.
What parts make up a compression layer?
The main component is the concrete, for which a HA 25, comprising a minimum thickness of 40 mm on the joists and support members made of ceramic or concrete; of 50 mm when installed over interlayer materials of any other type (such as polystyrene) and in seismic zones with a design acceleration greater than 0.16 g.
Along with concrete is the welded wire mesh in a workshop-style setting B500T made of corrugated wire, which is used as reinforcement. The spacing between wires must not exceed 350 mm in either direction, with at least 4 mm in diameter of the reinforcement elements. As a guideline for the quantity (for Spain), we recommend following the specifications in the Table 42.3.5 of the EHE-08 (in Spain).
What are the key factors for properly installing a compression layer?
1. Dosage
Ideally, it would be great to have a ready-mix concrete, with the strength and consistency specified by the builder. In this case, it is recommended to specify concrete, at least H 17, with a maximum slump of 7 cm so that it is not too fluid, and a water-to-cement ratio of 0.50 to 0.55.
If dosing on site:
- 1 part cement.
- 2 parts sand (3 if it's very wet).
- 3 parts stone.
It is essential to take into account the factors that influence the strength of concrete. In fact, the accuracy of the materials and the control of the mix are related to other structural elements, such as the Types of Connecting Rods, Their Function, and Applications, which are also essential for transmitting loads within building systems.
2. Straining
At this stage, it is recommended that Thoroughly wet the beams and vaulted ceiling tiles prior to pouring the concrete so that they are saturated with water. It is also important to pay attention to the surrounding weather conditions, considering that In winter, concrete should never be poured at temperatures below 5 °C, and in summer, it is best to avoid the hours around noon..
When installing the electro-welded mesh, it is important to distribute the fresh concrete so that it does not accumulate excessively in any part of the floor slab, avoiding point loads on the joists. These recommendations apply to both concrete mixed on-site and concrete mixed at a plant.
Concrete pouring process. Source: Hemoeco
3. Curing
The final strength of the concrete depends on this phase, and contrary to what many people believe, Simply sealing the pores and cracks with cement grout is not enough to fix poor curing.. Proper curing of concrete is closely related to the hydration of the cement, and what must be avoided is abruptly depriving it of moisture.
So what you need to do is Maintain as consistent a level of moisture as possible during the hydration process of the cement, so that the particles, as they gradually hydrate, do so uniformly, preventing cracks and surface fractures. Various methods are used for this. (Learn about them here)
Concrete curing process. Enriquelario.com
If all of the guidelines mentioned above are followed, the result will be a compression layer properly bonded to the joists, which results in improved mechanical performance of the floor slab. This provides adequate and sufficient strength to fulfill its role in distributing loads horizontally to the building’s other structural elements.
