Study on the Cleaning of Stone Water Spots in Building Decoration

With the increasing use of stone in the construction field, the stone disease that accompanies it also plagues more and more builders and owners. These diseases not only greatly reduce the decorative effect of stone, but also shorten the service life of the stone. In many stone diseases, water spots or water marks are one of the most common chronic diseases. Stones with water spots or traces of water are like a big face because of the uneven wet or dry stone surface, which makes the original natural and luxurious decorative effect of the stone greatly reduced. Especially for some large-scale stone decoration works, water spots are often of engineering quality. From the current treatment technology, it is very difficult to remove the water spots or water marks of the stone. The literature review also shows that there is very little research at home and abroad. Some people even called this water spot or water mark as a stone decoration project. cancer. Therefore, how to eliminate or prevent this chronic disease has become a very realistic research topic.

(1) Causes of water spots or water marks

As a chronic disease of building decorative stone, water spots or water marks mainly refer to wet marks on the surface of already decorated stone or traces of scars like wet marks. The main feature is that these wet marks are always dry; or they are not easy to completely dry; Or people always feel that there are traces of water wetting. Even if it is exposed to sunlight or baked with fire, the wet marks remain afterwards. The cause of stone water spots or water traces is related to the analysis of the formation conditions, the nature of the stone itself, the surrounding environment, and the installation and construction methods. Stone has a lot of micropores, which are microporous materials, mostly one. Stone is also hydrophilic, it can automatically absorb moisture and transfer moisture. There are mainly four types of water spots or traces of water on the surface of decorative stone that are formed from the formation mechanism:

The first is when the stone is directly or indirectly connected to moisture or water. For example, wet surfaces and walls in the southern part of the country, or parts of the nearby water that often seep out of water, can often see wet blots on the stone surface near the stone crevices.

The second reason is that some salts or alkalis are contained in the micropores of the interior or surface of the stone. These salts or bases are often affixed with water as the surface of the stone evaporates, and subsequent water supplements continuously concentrate the salt and alkali on the surface layer of the stone. There are two types of water spots formed by salt and alkali. One is a number of easily deliquescent salts or alkalis. They have low water vapor pressure, so they will absorb water until they reach equilibrium with the external water vapor pressure, and the micropores of stone produce The additional pressure (microporous capillary phenomenon) makes the balance more conducive to the absorption of more moisture, so regardless of the outside weather, the surface of the stone is always dry. The other is the translucent crystals of some salts, which occupy in the micropores of the stone, which change the reflectance of the surface light. The rough looks like the stone is wetted.

The main sources of salt and alkali on the stone surface layer are: 1) the saline-alkali components of cement, mud mortar or additives when wet-processed; 2) the soluble saline-alkali that migrated with water in nearby soils or groundwater; 3) after environmental pollution or acid rain The sediment; 4 stone in the mining, processing, handling and open storage when brought into the salt, such as cutting saws and polished coolant; 5 stone after the installation of cleaning fluid and care solution, etc. into. The third type is the water spot formed by the minerals of the stone itself. In addition to some of the soluble salts and unstable chemicals contained in the stone itself, some of the stone's interior contains inclusions. These inclusions are foreign substances that are “captured” by the rock during its formation. They may be gaseous, liquid, or Solid form exists. When the rocks are cut, some of them gradually spread out to form scars, and some marks only make the local color a little darker, much like the wet marks of water.

The fourth is a blot similar to a water spot that has already dried. The reason for this is the wet adhesion, or the infiltration of water, the moisture under the decorative surface, or the infiltration of other damp viscous bodies, etc., to make the area of ​​the stone decorative surface wet for a long time. A wet surface absorbs dust more easily than a dry surface. Adsorption of dirt will penetrate the micropores of the surface of the stone over a period of time. Even if the entire decorative surface is dried afterwards, the blot of water spots expressed by the dirt will remain.

In the above four water spots (or water traces), the second most harmful to the stone is the existence of soluble saline and alkali. Salt crystal destruction (also known as salt weathering) has been considered as the most important threat to damage of stone buildings and stone artifacts.

(b) Removal of water spots or water marks

For the above causes of water spots (or water traces), the methods of removal are different: the first one needs to remove moisture or cut off the water source; the second is to remove the salt or alkali in the micropores; the third and fourth kinds Need to remove color or dark material. The most common of the four water spots (or water marks) are the second and fourth species. This article also discusses the removal methods of these two water spots (or water traces).

At present, there are very few studies on water spot (or water mark) removal methods in foreign countries. Some can be found:

(1) In the U.S. patent, Shrin-Sarley mentioned a method for removing water marks and mineral deposits on hard surfaces. The main method is the cleaning of hard surfaces with viscous fluids using mineral acids, lubricants, and thickeners. . The role of mineral acid is to remove traces, such as calcium salts and precipitated metal oxides, with a preferred concentration of 31% to 37% wt. The lubricant is selected from glycerin or mineral oil, and this component can increase the dispersibility of the components, and its preferred concentration is 15% to 30 wt. The thickener may be gelatin or silica, or a mixture thereof, in a concentration range of 3 to 16% by weight of the total composition. In order to achieve a flowable and viscous effect, the final composition should have a viscosity in the range of 1.73 to 76000. Centipo. In addition, dispersants or deflocculating agents may also be added, for example surfactants using octadecane suspensions. When using colloidal silica, it is necessary to consider the size of the particles and the effect on the viscosity. The size of the particles is preferably 0.3-0.5 μm. If the solution is not stable, one or more dispersants or a mixture of deflocculants may be utilized. The amount of dispersant or deflocculant is about 40% or less of the total weight. Other related components can also be added, including dyes, fragrances, solvents or enzymes. The addition of these solvents or enzymes facilitates the dissolution of the soil mixture, which is claimed to efficiently, conveniently, and rapidly clean the porous and non-porous hard surface of dirt and the like. When the composition is in a high viscosity condition, such as 76000 centipoise, the cleaning agent becomes a gel. This facilitates the cleaning of vertical, angled, or inverted hard surfaces.

(2) Peter Chariri describes in another U.S. patent a bleach cleaner that removes water stains, it is said to remove dirt from walls and ceilings, and it is only necessary to spray or rub the cleaner on The surface of the stain can be done without excessive wiping of the surface. The cleaning agent is mixed with water when used in powder form to form an aqueous solution containing 3-8 wt% of solute. Powder formula: bleach 60 to 80 wt%, surfactant 0.1 to 10 wt%, water-soluble anionic polymer 0.1 to 10 wt%, other inert ingredients 5 to 40 wt%

(3) Hideo Yanon introduced a cleaning agent for stains on hard surfaces such as concrete, stone, brick and tile in Japanese patents. This is an aqueous cleaning agent consisting of 5 to 25 wt% of mixed acid (water stains are also mentioned therein), 003 to 1 wt% of fatty acids, 0.2 to 5 wt% of alkyl ethers, and 5 to 40 wt% of ammonium chloride.

(4) Seaweed-Dema et al. introduced a foam cleaner in Japanese patents for the cleaning of scale-type dirt on hard surfaces, especially inorganic dirt in bathrooms and toilets, and synthetic dirt in kitchens. Etc., It is said that there is a long-term protection after cleaning, the formula includes: serine or its salt 0.1 to 30wt%, water-soluble solvent 01 to 50wt%

(5) Nita Tai et al. introduced a cleaning agent capable of repelling water traces in Japanese patents, allegedly capable of cleaning water stains on the surfaces of ceramic products. Its formula is relatively simple, mainly composed of mixed solvent such as methyl chloride and isopropyl alcohol. The weight ratio of both methyl chloride and isopropyl alcohol is 9O-65. We have conducted experimental verification of some formulas that can be found as well as some products imported from abroad. As a result, it has been found that some formulas and products are not effective at all, and some formulas and products have some effects.

In order to develop a new type of stone water spot remover, combined with the graduation thesis work of undergraduate students, we conducted a variety of theoretical and experimental studies. A compound stone spot remover (ZDF25) has now been developed. It is an aqueous solution that meets the requirements of environmental protection and has been used in some cleaning projects. It has a better removal effect on saline spots and dirt type water spots or traces, namely the above-mentioned second type of water spot.

(c) Prevention of water spots or water marks

As mentioned above, water spots are hazardous and difficult to remove. As people become more aware of the causes of water spots, the prevention of water spots or water traces has gradually become the biggest concern for owners, designers and construction units of stone decoration works. According to the four causes of water spots, the commonly used pre-construction preventive measures are mainly the following:

(1) Since the stone is a hydrophilic microporous material, it will automatically absorb water and transfer moisture. Pay attention to blocking the water source, isolating the moisture and draining the water in time;

(2) Fill the capillary pores at the bottom of the stone to protect the stone base so as to block the salt and alkali components in the cement, mortar or admixture, as well as the soluble salt and alkali in the nearby soil or underground water. Stone base protective agent composition is mainly organic polymer resin or inorganic colloid, and most of them are film-forming materials;

(3) Surface protection (waterproofing) is applied to the front and sides of the stone to prevent salt, alkali or dirt from being carried by people due to construction, environmental pollution, and cleansing care. Most of the commonly used surface protection agents are silicon or fluorine (organic or inorganic) compounds, which have certain permeability and hydrophobicity, and most of them have no obvious film layer and have a certain permeability; (4) choose a chemically stable stone To avoid the formation of scars due to changes in the mineral composition of the stone.

In short, water spots or traces of stone is a stone disease that is more difficult to cure, and taking preventive measures in advance is the most economical method. If we already have water spots or water traces, we currently have a chemical removal method. The most critical thing is to prescribe the right medicine.

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