In the field of constructions is known the use of cementitious mortar products with properties of transparency to light. According to a first known embodiment (described, for example, in patent application WO03097954), such cementitious mortar products are made in the form of cementitious mortar blocks internally crossed by optical fibers which permit the transmission of light from one side to the other of the block itself. In particular, the optical fibers are located as a warp in meshes or special fabrics, and are thus inserted in cementitious mortar poured into formworks to provide blocks of variable dimensions in relation to their end use. Plates or panels, which are finally subjected to smoothing and polishing, are thus obtained from such blocks.
Only after such operations the above-described transparency effect can be achieved, which is however conditioned by the intensity of the incident light on the block and by the angle of incidence of the same, beyond a given value from which the transparency effect determined by the transport of light by the optical fibers gradually decays, this being an evident limit of such a technique. Another drawback of the above-described solution is found in the complex positioning of the optical fibers, which requires to prepare a particular fabric as a support to be inserted in subsequent layers into the formworks, alternating with layers of cementitious mortar; furthermore, additional steps of cutting and polishing are required in order to obtain plates or panels from the blocks, which steps imply waste of costly material (optical fibers), especially when parts of considerable size are needed, such as square plates longer than one meter per side.
It is equally known that the limits and drawbacks of the aforesaid solution have been overcome by using composite cementitious mortar panels comprising translucent elements which extend through the entire thickness of the panel. In this regard, patent application EP 2376718 describes some embodiments of such composite material in which the translucent elements are made of PMMA. In order to obtain such panels, the PMMA elements are firstly positioned in a formwork and arranged according to parallel lines by taking advantage of appropriate spacers which keep the elements reciprocally spaced apart. The formwork is then filled with cementitious mortar to embed the PMMA elements.
With respect to the solutions requiring the use of optical fibers, the use of the translucent elements described in EP 2376718 has been proven to be much more effective because the transparency effect is however achieved even in the presence of unfavorable light angles.
However, it has been observed that the panels with elements made of PMMA have some drawbacks which require a solution in order to make this technology easily usable. With reference again to the solution described in EP 2376718, the elements made of PMMA are shaped as longitudinal elements characterized by stretches having a thickness equal to that of the panel and connected by stretches of lower height according to a substantially “chain-like” development.
It has been seen that the cost formation of each “chain-like” element is determined by two main components, the first of which is the cost of the material, namely of the rectangle made of PMMA from which the “chain” is obtained. The second component is instead determined by the cost of the laser beam cutting process, which is considered to be the best practice in the prior art.
It has been additionally observed that the production process of the panels includes a substantially crafted, and in particular a manual, arrangement of the chains in the formworks according to a predetermined arrangement which requires particular care and diligence by workers, the simultaneous use of multiple formworks and the cementitious mortar pouring operations which are made rather problematic by the need to fill one mould at a time. It results in that the crafted production process is obviously accompanied by particularly high management costs.
Furthermore, it has been observed that panels in which the chains are arranged in irregular manner having poor parallelism and lacking in rectilinearity are often obtained in the above-described production process. This firstly compromises the good appearance result thereof. Finally, it is worth noting the poor flexibility of the method when productions of panels with different sizes are required because the availability of formworks provided with sides of different lengths and/or heights is required.
A final drawback of the solution described in EP 2376718 is found in the substantial impossibility to use other materials, besides PMMA, for manufacturing the translucent elements. The choice of PMMA was dictated from the beginning by the need to use a material having good translucence features, good resistance to alkali and high tenacity in order to reduce possible rejects/breakages during the step of manufacturing the panels. While satisfying the aforesaid requirements, the PMMA elements have a high water absorption coefficient (about 2-3%) and a thermal expansion coefficient of one order of size higher than that of the cementitious mortar used. These aspects are particularly critical for the structural integrity of the panel. For this reason, in order to reduce the absorption capacity of the PMMA elements (and their consequent swelling due to absorption of water, in particular from the cementitious mortar) a preliminary step of saturating the elements in water for at least 24 hours at a temperature of about 45-50° C. is required. This aspect also significantly impacts on the process. Indeed, this preliminary step, although not particularly demanding, requires the availabily of workers and the use of a tank for storing the elements made of PMMA in hot water. Additionally, it has been seen that in order to reduce the risk of cracking due to thermal incompatibility, high dosages of fibers (preferably stainless steel) are often employed and substances (latexes) capable of attenuating the modulus of elasticity at least on the short term are used in the cementitious mortar mixture. Therefore, the possibility of using materials alternative to PMMA could allow a further reduction of the process costs. In this regard, the use of glass could represent an excellent alternative to PMMA because glass has a better thermal compatibility with cementitious mortar (and a better fire reaction than PMMA), the optical properties being substantially equal. Despite this evidence, it is unthinkable to make the elements described in EP 2376718 of glass due to their particular chain shape which is impossible to obtain. The poor tenacity (i.e. the high fragility) of glass would make positioning the elements in the formwork even more difficult and the subsequent pouring operation could cause the breakage of the elements themselves.
The need to have a new method for the production of the translucent panels which allows to overcome the aforesaid drawbacks and firstly allows to drastically reduce production costs and simultaneously increase end product quality clearly arises from the above. The need to have a new method for the production of such panels which allows to use light radiation transmission elements made of materials alternative to PMMA equally arises.
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