At the stone processing plant, products are made from blocks in the form of stone cladding, architectural-construction or construction-road details.
In the quarry, from the perspective of color and pattern, there was only the possibility of examining the surface of the block, its faces; there was no way to "look" inside the block, into its central parts. This is where the possibility of encountering "defective" areas in the blanks during the sawing of blocks lies. Even in granite blocks, small areas of a different color and pattern, so-called schlieren, can be found. For example, in granite, up to 5% of blanks were found to include black schlieren of gabbro-diabases and pegmatitic cavities (Fig. 1).
🔍Fig. 1. Inclusions of dark spots of gabbroids in blanks of light pink granites
The production of stone cladding parts from such blanks will inevitably lead to their rejection. In order to save costs, it is advisable to reject such blanks at the initial stage of the stone processing process. Naturally, when processing sedimentary or metamorphic rock, there may be many more defective blanks.
In Jurassic limestone, especially of a gray hue, there may be inclusions of pyrite, which subsequently have a very negative impact on the appearance of the facade of the entire structure. As a rule, these inclusions are characteristic of layers of Jurassic stone from the 1st to the 6th. That is, this is precisely Jurassic marble of a gray-blue hue (Jura PolarBlau). Conscientious suppliers always ask their potential clients about the application of this stone (facade or interior).
In Fig. 2, the pyrite stains on the rejected blocks of Jurassic limestone at the Petersbuch quarry in Germany are visible.
🔍Fig. 2. Pyrite inclusions and streaks on Jurassic stone blocks
When controlling the quality of stone products, it is also necessary to pay attention to the control of decorative parameters of the stone, its mineralogical properties, and radioactivity, although the main issue at this stage is the control of the geometric parameters of the products and the quality of the textured processing.
Based on our experience, during the final inspection of granite products, up to 6% (Fig. 3) of the products may be rejected due to the presence of technogenic cracks and non-compliance of geometric parameters with the working drawings. Technogenic defects are also found in Jurassic limestone, which, unfortunately, sometimes reach the facade of a very expensive elite apartment complex in the center of Moscow (Figs. 4-5).
It would also be useful to organize incoming inspection of stone elements before their direct installation. At this stage of stone cladding, defects in the elements can occur for several reasons. These are elements that were not covered by outgoing inspection due to technical, and more often, administrative errors.
In addition, some defects on the parts occur during their packaging, transportation, unloading, pre-assembly preparation, and assembly. (fig.2).
🔍Fig. 2.1 Technogenic crack on a granite slab, formed during its production or transportation. The crack was detected during incoming inspection.
🔍Fig. 3. Technogenic crack on a slab of Jurassic marble, which occurred during its production or transportation. The crack was not detected by incoming inspection.
🔍Fig. 4. Technogenic crack on a slab of Jurassic marble, which occurred during its production or transportation. The crack was not detected by incoming inspection.
🔍Fig. 5. Technogenic crack on a slab of Jurassic marble, formed during its production or transportation. The crack was not detected by incoming inspection.
Normal quality stone cladding
We would like to once again draw the attention of our colleagues in the stone business to the fact that, in our opinion, it is impossible to ensure proper quality of stone cladding without organizing quality control of the stone and products made from it at all stages of production. According to our estimates, up to 70% of objects with stone cladding require repairs after just a few years of operation.
Unfortunately, we have already gotten used to stepping on rakes in our activities, and several times at that. This article is for those who prefer to learn not from their own rakes, but from the experiences of others. I would like to emphasize once again that free cheese is only found, you know where, and a miser pays at least twice. These selective examples are the result not only of a lack of control, as it is very costly to monitor every slab; it is much more beneficial to initially choose a conscientious manufacturer who values their reputation and name.
This partnership will save you from wasting nerves, time, and of course, money. It is no secret that elite houses built in the turbulent 90s have partially lost their status and shifted into the so-called business class. Even their location can no longer correct the flaws caused by the use of low-quality materials, unprofessional installation teams, etc.
The market for luxury homes and apartments is becoming increasingly competitive. Investing in expensive real estate not only as a residence but also as a liquid asset is an important aspect of the choice for affluent buyers. What can be said about an expensive building whose facade will soon turn into an unsightly mosaic of low-quality stone?