Gypsum board mouldy reason and solution

China's gypsum plasterboard was born in the 1980s. After more than ten years of market cultivation, with the reform and opening up and the rapid development of the national economy, the domestic demand for gypsum plasterboard has increased greatly, and the production and sales records have been refreshed frequently. With the continuous improvement of people's understanding of gypsum board, the application field of gypsum board has gradually entered home decoration from large-scale industrial and civil engineering. Paper faced gypsum board has become the necessary material for all kinds of interior decoration at present because of its good quality and low price, green, environmental protection, health, fire prevention, breathing, simple construction and other characteristics
During the sales of dealers, the construction of decoration teams and the use of consumers, the mildew problem of gypsum board appeared, which caused confusion or product quality concerns and quality complaints. Mildew of various items (including gypsum plaster board) is mainly concentrated in coastal areas, along rivers, along lakes and other areas with high relative humidity, especially in summer when it is hot and rainy, which is a high incidence period of mildew. This paper will analyze the growth conditions of mold, the product components of gypsum board and the causes of mold, and put forward feasible solutions.
1 about mold and mildew
Mold is a kind of multicellular microorganism, which widely exists in nature and belongs to fungi in microbiology. Mold is everywhere in our life. It prefers dark, warm and humid environments. In such environments, it will multiply rapidly.
When the article changes color and deteriorates due to mold growth, it is "moldy". The rapid growth of mold requires three conditions: first, air (specifically oxygen), which requires long-term contact with air; Second, suitable temperature and humidity, especially in dark and humid places. Generally, when the temperature is more than 23 degrees Celsius and the relative humidity is more than 70%, mold will multiply rapidly; The third is the nutrient source, such as starch, protein, fiber and other carbohydrates.
2. Variety, composition and core structure of gypsum board
2.1 types of gypsum board
According to the national standard cb/t9775-2008 gypsum plasterboard, gypsum plasterboard can be divided into ordinary type, water-resistant type, fire-resistant type and water-resistant fire-resistant type according to its function, compared with ordinary board. The water-resistant board reduces the surface water absorption and water absorption of the board by using the special protective paper treated with water resistance and adding waterproof agent into the gypsum core; By adding an appropriate amount of inorganic glass fiber into the gypsum core, the fire-resistant board improves the stability of the board in case of fire; Water resistant refractory board is the combination of the above two.
2.2 composition of gypsum board
Whether ordinary board, water-resistant board, fire-resistant board or water-resistant fire-resistant board, it is composed of face paper and gypsum core. Among them, the main components of face paper are fiber and starch sizing agents, and the main components of gypsum core are calcium sulfate dihydrate and a variety of auxiliary additives, which also contain a small amount of starch reinforcing agents: carbohydrates (fiber and starch) in face paper and gypsum core can provide nutritional sources for mold.
2.3 board core structure of gypsum board
There are a large number of honeycomb microporous structures in the core of gypsum board, so it can regulate the indoor air humidity. Therefore, gypsum board is vividly called "breathable material". When the indoor air humidity is high, the gypsum plaster board will absorb the water vapor in the air and store it, and then release it when the indoor air humidity is low. Within the adjustable range of gypsum plaster board, the indoor air humidity balance is maintained. However, if the indoor air humidity is too high, beyond its adjustable range, the respiratory function will fail, and a large amount of water will accumulate in the gypsum board, which will create favorable conditions for mold breeding.
3. Reasons for mildew of gypsum board
3.1 reasons for mildew during storage
The paper faced gypsum board has taken moisture-proof measures when leaving the factory, such as the whole package is wrapped with a plastic cover or wrapped with a plastic stretch film. If it causes damage during transportation or handling, plus the long sales cycle, open storage or excessive humidity in the warehouse, the warehouse is closed and poorly ventilated, and there is rain, water leakage or condensate dripping on the gypsum board, it is easy to cause moldy gypsum board under warm weather conditions: it should be noted that serious moldy board surface will reduce the quality of gypsum board, and moldy surface will cause structural damage to the protective paper. The strength of paper faced gypsum board is its key performance index. Both face paper and gypsum core contribute to the overall strength of paper faced gypsum board, with a contribution ratio of about 6:4 (only taking the thickness of 9.5mm as an example, the contribution ratio of plates with different thickness will be different). The structural damage of the protective paper caused by mildew will greatly reduce the strength of the plate, and the qualified products will become unqualified products.
3.2 causes of mildew during construction and use
First, the external climate conditions during construction and use are poor, such as high temperature and continuous rain for several days, and the air humidity in the areas near the sea, river and lake is high for a long time. Second, the space is narrow and airtight. According to statistics, a large number of mildew accidents almost occur in home decoration projects, and are basically concentrated in basements and toilets, while there are almost no such accidents in large projects. Third, the humidity of the wall or floor under construction is relatively high. The construction team starts construction before the water of the wall or floor evaporates, so that the gypsum plaster board is in a high humidity environment for a long time. Fourth, there is rain leakage, water leakage or condensation water from the air conditioning pipe dripping on the gypsum board. The above conditions have created favorable conditions for the large-scale growth and rapid propagation of mold.
4 feasible solutions
4.1 warehousing process
First, ventilation measures or other dehumidification measures should be taken to reduce the humidity in the warehouse; Check whether there is water leakage, rain leakage or air conditioning condensate dripping on the gypsum board and solve it thoroughly; Check whether the outer package of the product is damaged and whether the product has mildew, evaluate the degree of mildew and its impact on product quality, and decide whether to sell normally or downgrade.
4.2 construction process
First, ventilation measures or other dehumidification measures should be taken to reduce the humidity of the construction environment; If there is rain leakage, water leakage or air-conditioning condensate dripping on the gypsum board, it should be thoroughly treated; Reduce the water content of walls and floors; The next construction shall be carried out when the overall environment is relatively dry. Scrape away the mildew with a shovel, and evenly spray it on the surface with 84 disinfectant. After drying, apply waterproof primer 2 to 3 times. After the waterproof primer is dry, the decoration can be carried out according to the normal procedure. During construction, pay attention to observe the mildew degree of gypsum board and the impact on product quality. If it is serious, it should be replaced.
4.3 use process
Pay close attention to indoor air humidity, especially in continuous high temperature, rainy weather, take necessary ventilation and other dehumidification measures to effectively reduce indoor humidity; Check whether there is water leakage and rain leakage in the room, as well as the dripping of condensate on the air conditioning vent and pipe surface; Places such as basement, toilet and wall corner with poor ventilation are most prone to mildew, so the desiccant can be changed regularly to maintain low humidity. When mildew occurs, the repair measures in 4.2 can be taken.
5 relevant national standards and construction specifications
Although the relevant national standards and construction specifications do not stipulate the specific construction temperature and humidity range, they also stipulate the construction requirements. For example, the national building standard design atlas 07cj03-1 "light steel keel gypsum board partition wall and ceiling" stipulates that the installation site should be ventilated, clean and dry, and the ground should be free of water, dirt, oil, debris, etc., so as to avoid construction in rainy seasons and high humidity environment. The national standard gb50327-2001 code for construction of residential decoration engineering clearly stipulates that corresponding measures should be taken for the transportation, handling, installation and storage of ceiling materials. Prevent moisture, deformation and damage to the surface and corners of the plate; Light partition materials shall be handled with care during transportation and installation, and the surface and corners shall not be damaged. Deformation due to moisture shall be prevented.
6 Conclusion
The technology and raw materials of gypsum board determine that it contains certain carbohydrates, which provides a condition for mold growth and reproduction. The board core structure makes it have unique breathing function, which determines that the paper gypsum board has good moisture absorption performance. Just as steamed bread and rice are easy to mildew under high temperature and humidity, if the storage, construction and use environment of gypsum board is improper, mildew will also occur. Relevant national standards and construction specifications have made requirements for storage and construction environment. Fundamentally speaking, moldy gypsum board is not a product quality problem. No matter whether the water-resistant board, fire-resistant board or water-resistant fire-resistant board, although the formula is different, they also contain substances such as fiber and starch. Therefore, mildew may occur when the temperature and humidity conditions are met. Even the products on the market that claim to be "antibacterial and mildew proof gypsum board" can only meet the requirements of the national standard for antibacterial and mildew proof under the 28 day inspection environment. With the passage of time, if they are in the high temperature and humidity environment for a long time, when the effectiveness of the drugs is consumed, mildew will still appear.
Therefore, in order to fundamentally solve the mildew problem of gypsum board, we must solve the problem of high temperature and high humidity, and the most important thing is to solve the problem of high humidity, and fundamentally eliminate the conditions for mold survival and reproduction.