Concrete slab
[1][2] In many domestic and industrial buildings, a thick concrete slab supported on foundations or directly on the subsoil, is used to construct the ground floor.
Concrete has a relatively high thermal mass, meaning that it takes a long time to respond to changes in ambient temperature.
[9] This is a disadvantage when rooms are heated intermittently and require a quick response, as it takes longer to warm the entire building, including the slab.
However, the high thermal mass is an advantage in climates with large daily temperature swings, where the slab acts as a regulator, keeping the building cool by day and warm by night.
Thus, when a concrete slab is subjected to fluctuating temperatures, it will respond more slowly to these changes and in many cases increase the efficiency of a building.
[5] In reality, there are many factors which contribute to the effect of thermal mass, including the depth and composition of the slab, as well as other properties of the building such as orientation and windows.
[11] This not only allows for better insulation but decreases the weight of slab which has a positive effect on load bearing walls and foundations.
Ground-bearing slabs, also known as "on-ground" or "slab-on-grade", are commonly used for ground floors on domestic and some commercial applications.
This results in cracking and deformation, potentially leading to structural failure of any members attached to the floor, such as wall studs.
[13] In addition to filling the downhill side, this area of the slab may be supported on concrete piers which extend into the ground.
In this case, the fill material is less important structurally as the dead weight of the slab is supported by the piers.
[10] Without reinforcement, the entire load on these slabs is supported by the strength of the concrete, which becomes a vital factor.
As a result, any stress induced by a load, static or dynamic, must be within the limit of the concrete's flexural strength to prevent cracking.
[19] Since unreinforced concrete is relatively very weak in tension, it is important to consider the effects of tensile stress caused by reactive soil, wind uplift, thermal expansion, and cracking.
[21] This makes them economical and easy to install for temporary or low-usage purposes such as subfloors, crawlspaces, pathways, paving, and levelling surfaces.
[10] In this application, a mud slab also prevents the plastic bar chairs from sinking into soft topsoil which can cause spalling due to incomplete coverage of the steel.
The calculation of reinforcement requirements for a one-way slab can be extremely tedious and time-consuming, and one can never be completely certain of the best design.
[24] This may be implemented due to application requirements such as heavy loading, vibration resistance, clearance below the slab, or other factors.
If the slab is to be reinforced, the rebars, or metal bars, are positioned within the formwork before the concrete is poured in.
[26] Plastic-tipped metal or plastic bar chairs, are used to hold the rebar away from the bottom and sides of the form-work, so that when the concrete sets it completely envelops the reinforcement.
For a suspended slab, the formwork is shaped like a tray, often supported by a temporary scaffold until the concrete sets.
On commercial building sites, plastic and steel are gaining popularity as they save labour.
[27] On low-budget or small-scale jobs, for instance when laying a concrete garden path, wooden planks are very common.
