The corrosion and disease of stone determine the necessity of stone maintenance. Stone has a complex and fine microscopic and chemical structure. The main components of marble are carbonate, such as calcium carbonate and magnesium carbonate. When they encounter acidic substances or sulfur dioxide in the air, they are easily changed into water-soluble ions under the action of water and are corroded. Although the main component of granite and sandstone is silicate with high stability, there are many micropores on their surface and inside, which are the channels for dirt, water and gas to enter the stone.
Therefore, under the influence of external environmental factors such as water, salt, atmosphere, acid rain, biology, industrial smog, and domestic waste, through physical, chemical, biological and other destruction mechanisms, various damages and "diseases" such as white China, wet marks, yellowing, weathering, cracking, fading, and human pollution (oil stain, cement mortar, pigment) occur to the wood. The specific causes of these phenomena have been described in relevant literature. However, it is worth pointing out that in recent years, the air quality in many areas of our country can not even meet the national Class III standard, and the damage of environmental pollution to stone materials is increasing, which should be paid more attention to.
The maintenance of stone is also an important measure to improve the quality and grade of stone in China. In 2000, China's stone output exceeded 6 million m, making it the largest stone production country in the world. However, China's stone exports are still second to Italy, with primary processing products such as raw stones and rough boards as the main export products, accounting for more than 40% of the total output. Italy, on the contrary to China, is dominated by finished stone products. Their fine stones have been carefully treated almost before the finished products. Obviously, the backward chemical deep processing technology of stone in China leads to low product grade and added value, which is one of the important bottlenecks restricting the development of China's stone industry. It is inevitable that China's stone production process will be closer to the world. China is expected to join the World Trade Organization this year, which is a rare opportunity and a huge challenge for Chinese stone enterprises. Therefore, in order to change the strength of Chinese stone from big to strong, the pre care and chemical deep processing technology of stone must go first.
Stone conservation in developed countries in Europe and America started early, with a strong and conscious concept of stone conservation, and advanced and stable related technology and equipment. In contrast, there is still a certain gap between China and them, which should be improved at least from the following points.
First of all, establish a correct concept of stone maintenance. In particular, the acceptance of the stone conservation concept by the construction project's Party A is particularly important. At present, the majority of onlookers are hesitant about stone maintenance, most of them still stay in the passive situation of "headache cures the head, foot pain cures the foot", and the proactive preventive measures of "prevention in the bud" have not really been implemented. In addition, stone care usually only stays in the daily maintenance during or after use, and does not go deep into the pre maintenance of stone before delivery. According to the analysis of insiders, the curing rate of building stone in China is still less than 10%. If the competent department of the industry considers to introduce some regulations, it may be conducive to further promoting the development of the stone conservation industry. Indeed, some people mistakenly believe or exaggerate the effectiveness of stone curing. In fact, the maintenance of stone can effectively prevent the occurrence of various stone diseases, and effectively maintain the natural and beautiful natural color of the stone, but it does not mean that the stone can be maintained once and for all, or even eliminate all diseases.
Secondly, we must improve the evaluation standard of stone maintenance. At present, there is no industry standard or even enterprise standard for the effect of stone curing in China, and the evaluation methods are different, leading to some confusion in the stone curing market. At least, it is unscientific and not comprehensive to use the water absorption rate of stone as the only evaluation standard of stone curing agent at present, and there are different test methods in different test units, and the water resistance of the same curing agent to stone with different porosity is also different. Therefore, the introduction of a unified and scientific test method is particularly urgent.
Thirdly, the task of developing high-grade stone curing agent with independent intellectual property rights is very urgent. At present, stone curing agents produced in the United States, Germany, Japan, Italy and other countries still occupy the domestic market. Their products have stable performance, but their prices are very high. They earn tens of millions of dollars of foreign exchange from China every year. However, the domestic stone curing agent is mainly of medium and low grade, which has no market competitiveness and occupies a small market share. On the one hand, it is related to the late start of China's stone maintenance industry; On the other hand, the intersection between stone and chemical industry is not enough. Although China has sufficient scientific research and development capacity, due to the constraints of the existing scientific research system, scientific research and productivity are seriously disconnected, resulting in the development and transformation of new products lagging behind.
Fourth, a professional stone maintenance team must be established. Some domestic construction units should say that they are not experienced enough to correctly understand and use the stone curing agent, and even cause unnecessary losses. The good and bad construction of stone curing will directly affect the project quality The maintenance of stone materials shall be protected according to materials. For example, granite and marble generally have low requirements for curing agent, while sandstone and fire plate have high water absorption, so the curing agent with good sealing and permeability shall be selected. Different curing agents should also be used for different parts of stone materials. For example, in the kitchen and parking lot, protective agents with certain oil resistance should be selected. The protective agent on the back of wet pasted stone materials should have certain water pressure resistance and alkali resistance. The maintenance of exterior walls and stone cultural relics has extraordinary weather resistance. However, no matter which curing agent is selected, it is recommended to make small samples before construction in large areas to test its protective performance.