thermal conductivity of concrete slab
Thermal … Print. A non-reinforced slab is two-way if it is supported in both horizontal axes. < © 2016 The Authors. l [4] 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. Due to the poor thermal conductivity of concrete, diurnal temperature effects produce temperature gradients in concrete section; these gradients result in rotational distortions that produce stresses in the structure .The temperature gradient that forms is governed by the heat flow through the body and is a function of the density (ρ), specific heat (c) and thermal conductivity of concrete (k). [7] This is relatively high when compared to other materials, for example the conductivity of wood may be as low as 0.04 W m−1 K−1. In some special cases, the thermal properties of concrete have been employed, for example as a heatsink in nuclear power plants or a thermal buffer in industrial freezers.[5]. For a suspended slab, there are a number of designs to improve the strength-to-weight ratio. [24] In other words, if the axial ratio is greater than two, a two-way slab is required. This results in cracking and deformation, potentially leading to structural failure of any members attached to the floor, such as wall studs. [4] The R-value does not consider thermal mass, since it is tested under constant temperature conditions. Subsequently, Valore (1980) developed another formula in terms of overall density. x c p), which means that all variables are put together and the scatter of the different physical properties can be “equalized”. [9] Without reinforcement, the entire load on these slabs is supported by the strength of the concrete, which becomes a vital factor. Effective Span. In some cases formwork is not necessary - for instance, a ground slab surrounded by brick or block foundation walls, where the walls act as the sides of the tray and hardcore (rubble) acts as the base. [9] It is vital that the wall supporting structure is built to the correct dimensions, or the slabs may not fit. The actual value of k varies significantly in practice, and is usually between 0.8 and 2.0 W m−1 K−1. With the purpose of determining the strength of the reinforced concrete slab to withstand heat transfer, it is necessary to estimate R-value and U-value of the reinforced concrete slab under consideration. In some cases, a naturally sloping site may be levelled simply by removing soil from the uphill site. This concept is known as concrete cover. [9] However, there are still uses for a slab that is not insulated, for example in outbuildings which are not heated or cooled to room temperature (see § Mud slabs). Concrete has low thermal diffusivity, high heat capacity, and its thermal mass is negatively affected by insulation (e.g. A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. On uneven or steep surfaces, this preparatory measure is necessary to provide a flat surface on which to install rebar and waterproofing membranes. "Concrete in Practice 11 - Curing In-Place Concrete", "Clearing the confusion on 'plain concrete, "Rupture depth of an unreinforced concrete slab on grade", "What is the difference between one way and two way slab? For a ground-bearing slab, the formwork may consist only of side walls pushed into the ground.
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