While it's not a commonly used construction method in rural areas, in the urban area, paving block structures have gained in prevalence due to their practicality. Unfortunately, when it comes to rigidly-laid paving block structures (structures with mortar filled vertical joints), cracks, which are often caused by thermal stresses, are a common damage pattern. In addition to the mechanical issues caused by such cracks, they also affect the visual appearance of these, not damaged to the point where they are very attractive. This has a significant impact on the general belief in and acceptance of this construction, and as a result, the frequency of it increases. Thermal stress results in cracking in paving blocks, which makes them lose their integrity. Many factors contributed to this poor performance, and one of the most significant was the absence of appropriate design codes for the construction of rigidly laid paving block structures. It was only until now that they have been regarded as a special construction method in the German-speaking region. As a means of ensuring against possible damage due to temperature change, both guidelines advocate the use of expansion joints, where the latter also mentions the advantageous influence of a strong adhesive bond between the paving blocks and the mortar bed. The majority of these recommendations are based on empirical observations and simple design rules, but the deeper mechanical explanations are missing. This was the main motivation for the present work, which aims to present the pavement structure's response to temperature loading as realistically as possible. These few fundamental considerations will be introduced ahead of Section 1.2 where the objectives of the present work will be discussed in greater detail.
Factors such as those discussed above apply to situations in which an available building material is subject to a temperature load. when the temperature increases, the body expands (positive strain) and when it decreases, the body contracts (negative strain) (negative strain). Deformations of the body are permitted as long as they are not blocked. The body is stress-free in this case. In the event that the temperature is not evenly distributed over the whole body, even if the deformations are not blocked, temperature-induced stresses may occur. It is important to remember that if two adjacent elements in a monolithic body are undergoing different thermal loads, their desired deformation is generally geometrides to be compatible. Due to this thermally induced stress, we can conclude that this is a problem. The representation of this is shown in Figure 2, which presents a theoretical model (implemented on paper) which describes two stacked layers of a plate (unaffected by friction on the bottom) being subjected to different temperatures. While the lower layer is maintained at the initial temperature of 0C, the upper layer is cooled to 20C now it is able to purchase paving slabs in UK.
The stresses caused by the normal forces in the longitudinal direction are displayed, where the compression in the lower layer and tension in the upper layer are shown. a very simple analogy of a two-layered plate would be to say that a paving block structure is one such plate with two additional layers on top. Since we can conclude that temperature changes, for example, rainfall or any temperature drop, may cause the stresses induced in the pavement blocks and in the bed of mortar, respectively, it is therefore apparent that temperature changes may affect the overall integrity of paving and may impact mortar strength. This distinction is significant in this respect: the initial temperature as well as the magnitude of the temperature drop are both significant. It stresses rise in relation to the difference between the initial temperature and the actual temperature, and cracks happen when the tensile stress exceeds the resisting tensile strength, which means that a low initial temperature helps to prevent cracks. Conversely, it may be that constructing at a low initial temperature, such as building in the winter, results in high compressive stresses in the summer. Due to the simplicity of the considerations involved, it is impossible to state the best initial temperature with absolute certainty. In colder weather, an initial low temperature may help to prevent cracks from forming. On the other hand, in warmer weather, the high initial temperature leads to less expansion and compressive stresses. Another thing is that it is impossible to talk about shear failure between paving blocks and the mortar bed. When the non-constant temperature distribution is present in a two-layered plate which is deformable, the plate will expand. The resulting normal stresses in the longitudinal direction are a result of a forced temperature field.