Exploring its causes mainly comes from three aspects: first, natural defects in the suture structure, second, excessive moisture and salt alkali, and third, rapid changes in temperature and temperature.
2.1. Salt alkali analysis reveals crystallization: The suture line of Egyptian beige stone is the weakest part of the stone, especially the suture line of organic and muddy components. The material structure inside the suture is relatively loose and has strong water permeability, making it easy to become a channel for water migration and evaporation. The suture is actually a structural surface and can also be seen as a natural gap in stone. During wet paving, soluble salts and alkali substances in cement mortar and other building materials will migrate to the surface of the stone with the water, and after the water evaporates, white crystalline substances will form at the gaps.
This precipitated crystalline material not only disrupts the aesthetics of the stone but also the stress of its crystallization often compresses and expands the gaps and pores of the stone, causing flaky or powdery peeling on the surface of the stone. The phenomenon of salt and alkali precipitation is more common when Egyptian beige is installed on the floor or wall of the bathroom, and the salt and alkali substances come from both the interior of the wall and the air and polluted liquids in the bathroom.
2.2. Enrichment and pollution of foreign substances (commonly known as black spots): The organic and muddy components within the suture line, due to their looseness and high water absorption, have a much lower strength than the carbonate components. They form linear depressions along the suture line on the surface of the stone, and local depressions may form.
The sunken area can cause the accumulation of foreign pollutants and also cause biological reproduction. If the enriched pollutants contain dust and humus brought about by human life, diet, and human activities, as well as dander and skin debris generated by animal metabolism, over time, a large number of microorganisms, such as enzyme bacteria, will breed, causing the color of the material in the sunken area to change or even turn black. The discoloration caused by this pollution is significantly different from the color and material composition of the suture itself, which has a significant impact on the appearance of the stone.
2.3. Collapse: Natural stone itself is a rigid material with a certain water absorption rate, which can undergo thermal expansion, cold contraction, and freeze-thaw when temperature changes. As mentioned earlier, the strength of the material in the Egyptian beige stone suture is lower than that of other major carbonate components of the rock. Most of the rocks at the suture site are in cross-contact, and the contact surface cannot be a straight and neat surface with a certain angle, or even acute angle contact. The wedge-shaped tip of the rock with sharp angles above is prone to fracture of the rock itself under external forces, resulting in the occurrence of the “debris collapse” phenomenon.
When stone is installed in areas with geothermal pipelines, thermal contact can cause thermal expansion and deformation of the stone, and the suture line changes from closed to open, or repeatedly changes with alternating cold and hot. Frequent deformation will inevitably cause structural changes, and the suture will completely become a continuous gap. The rocks on both sides of the suture will be in a suspended state, making it more prone to widespread “debris collapse” and detachment.
2.4. Linear depression: As mentioned earlier, linear depression mainly develops along the suture line, which is composed of multiple factors, including the material itself and the result of external stress. Often, after the crystal hard care or grinding renovation of Egyptian beige stone material, it is also found that the crystal hard care film shows obvious depression along the suture line. The reasons for its occurrence are as follows: the hardness of the suture material is low and it is easy to be polished off; Sharp edges are subjected to greater force during grinding, resulting in relatively more wear and tear; Acidic crystal hardening agents have strong permeability to carbonate stone materials and are more likely to penetrate into the interior of the suture line. The crystal hardening materials required for the suture line are more than those for other parts. Therefore, after crystal hardening treatment, the protective film formed changes with the substrate.