At the stone processing plant, products are made from blocks in the form of stone cladding, architectural and construction details, or construction and road elements.
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 is no opportunity to "look" inside the block, into its central parts. This is where the possibility of including "defective" areas in the slabs during the sawing of blocks lies. Even in granite blocks, small areas of a different color and pattern, known as schlieren, can occur. For example, in Granite, up to 5% of slabs were found to include black schlieren of gabbro-diabases and pegmatite cavities (Fig. 1).
🔍Fig. 1. Inclusions of dark spots of gabbroids in blanks of light pink granites
The production of stone cladding details 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 Jura Limestone, especially of a gray shade, there may be inclusions of pyrite, which can later have a very negative impact on the appearance of the facade of the entire structure. Typically, these inclusions are characteristic of layers of Jura stone from the 1st to the 6th. That is, this is precisely the Jura marble of a gray-blue shade (Jura PolarBlau). Conscientious suppliers always ask their potential clients about the application of this stone (facade or interior).
Figure 2 shows pyrite streaks on rejected blocks of Jura Limestone at the Petersbuch quarry in Germany.
🔍Fig. 2. Pyrite inclusions and streaks on Jura Limestone blocks
When controlling the quality of stone products, it is also necessary to pay attention to the control of the 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 outgoing inspection of granite products, up to 6% (Fig. 3) of 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 Jura Limestone, which, unfortunately, sometimes reach the facade of a very expensive elite apartment complex in the center of Moscow (Fig. 4-5).
It will also be useful to organize incoming control 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 control due to technical, and more often, administrative errors.
In addition, some defects on the parts appear during their packaging, transportation, unloading, pre-installation preparation, and installation. (fig.2).
🔍Fig. 2.1 Technogenic crack on a granite slab, which occurred during its production or transportation. The crack was detected during incoming inspection.
🔍Fig. 3. Technogenic crack on a Jura marble slab, which occurred during its production or transportation. The crack was not detected by incoming inspection.
🔍Fig. 4. A technogenic crack on a slab of Jura Marble, which occurred during its production or transportation. The crack was not detected during incoming inspection.
🔍Fig. 5. Technogenic crack on a slab of Jura marble, which occurred 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 its products at all stages of production. According to our estimates, up to 70% of projects with stone cladding require repairs within the first 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 experience of others. I would like to emphasize once again that free cheese is only found in a certain place, 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, but it is much more profitable 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 tumultuous 90s have partially lost their status and have 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 place of residence but also as a liquid asset is an important aspect of 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?