Reasons and solutions of mildew on gypsum board

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(1) about mold and mildew
Mold is a kind of multicellular microorganism, which exists widely in nature and belongs to fungi in microbiology. Mold is ubiquitous in our life. We prefer dark, warm and humid environments. In such environments, it will multiply rapidly.
When the article changes color and deteriorates due to the growth of mold, it is called "moldy". The rapid growth of molds requires three conditions: one is air (oxygen to be exact), which needs to be in long-term contact with air; The second is suitable temperature and humidity, especially in dark and humid places. Generally, when the temperature is above 23 ° C and the relative humidity is above 70%, molds will multiply rapidly and massively; Third, nutrition sources, 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 board, gypsum board can be divided into four types according to its functions: ordinary type, water-resistant type, fire-resistant type and water-resistant and fire-resistant type. The water-resistant board reduces the surface water absorption and water absorption of the board by using the special face protection paper with water-resistant treatment and adding a waterproof agent into the gypsum core; The fire-resistant board improves the stability of the board in case of fire by adding an appropriate amount of inorganic glass fiber into the gypsum core; The water-resistant and fire-resistant plate is a combination of the above two.
2.2 composition of gypsum board
Whether it is 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 the protective paper are fiber and starch sizing agents, and the main components of the 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 the protective paper and gypsum core can provide nutritional sources for molds.
2.3 core structure of gypsum board
The core of the paper faced gypsum board has a large number of honeycomb micropores, so it can regulate the indoor air humidity. For this reason, people vividly call the gypsum board a "breathable material". When the indoor air humidity is high, the gypsum board will absorb the water vapor in the air and store it, and release it when the indoor air humidity is low. Within the adjustable range of the gypsum 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 moisture 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
Moisture proof measures are taken for the paper gypsum board when it leaves the factory, for example, the whole package is wrapped with a plastic cover or wrapped with a plastic stretch film. If damage is caused during transportation or handling, and the sales cycle is too long, the warehouse is stored outdoors or the humidity is too high, the warehouse is closed and the ventilation is not smooth, there is rain, water leakage or condensed water dripping on the paper gypsum board, it is easy to mold the paper gypsum board under warm weather conditions: it should be noted that serious mold will reduce the quality of the paper gypsum board, and mold will cause structural damage to the protective paper. The strength of the gypsum board is the key performance index. Both the cover paper and the gypsum core contribute to the overall strength of the 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 thicknesses 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 areas near the sea, river and lake is high for a long time. Second, the space is narrow, airtight and unventilated. According to statistics, a large number of mold accidents almost occur in home decoration projects, and are mainly 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, and the construction team starts construction before the water in the wall or floor evaporates, so that the gypsum board is in a high humidity environment for a long time. Fourth, there is rain leakage, water leakage or condensed water from air-conditioning pipes dripping on the paper gypsum board. The above conditions have created favorable conditions for the large-scale growth and rapid propagation of molds.
(4) feasible solutions
4.1 warehousing process
First, take ventilation measures or other dehumidification measures to reduce the humidity in the warehouse; Check whether there is water leakage, rain leakage or air conditioning condensate dripping on the paper gypsum board and solve it thoroughly; Check whether the outer package of the product is damaged and whether the product is mildewed, evaluate the degree of mildewing and its impact on the product quality, and decide whether to sell normally or downgrade.
4.2 construction process
First, take ventilation measures or other dehumidification measures to reduce the humidity of the construction environment; In case of rain leakage, water leakage or air conditioning condensate dripping on the paper gypsum board, it shall be thoroughly handled; Reduce the water content of walls and floors; The next construction shall be carried out when the overall environment is relatively dry. Scrape off the mildew spots with a blade, and evenly spray 84 disinfectant on the surface. After drying, brush waterproof primer for 2 to 3 times. After the waterproof primer is dry, decoration can be carried out according to normal procedures. During construction, pay attention to the degree of mildew of gypsum board and its 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 and rainy weather, take necessary ventilation and other dehumidification measures to effectively reduce indoor humidity; Check whether there is water and rain leakage in the room, as well as the dripping of condensed water on the air conditioning vents and pipe surfaces; The basement, toilet and wall corner with poor ventilation are most prone to mildew, and the desiccant can be changed regularly to keep the humidity low. In case of mildew, 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 specify the specific construction temperature and humidity range, they also specify the construction requirements. As specified in the national building standard design atlas 07cj03-1 light steel keel gypsum board partition and ceiling, the installation site shall be kept ventilated, clean and dry, and the ground shall be free of water, scale, oil stain, debris, etc. to avoid construction in rainy season and high humidity environment. The national standard gb50327-2001 code for construction of residential decoration engineering clearly stipulates that corresponding measures shall be taken during transportation, handling, installation and storage of ceiling materials. Prevent damp, deformation and damage to the surface and corners of the plate; During transportation and installation, light partition materials shall be handled with care and shall not damage the surface and corners. Moisture deformation shall be prevented.
6 concluding remarks
The technology and raw materials of gypsum board determine that it contains certain carbohydrates, which provides a condition for mold to grow and reproduce. The board core structure makes it have a unique breathing function, which determines that the paper faced gypsum board has a 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. The storage and construction environment are required in relevant national standards and construction specifications. Fundamentally speaking, moldy gypsum board is not a product quality problem. Whether it is water-resistant board, fire-resistant board or water-resistant fire-resistant board, although the formula is different, it also contains fiber, starch and other substances, so when the temperature and humidity conditions are met, mildew may occur. 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 high humidity environment for a long time, mildew will still occur when the efficacy of the drugs is consumed.
Therefore, in order to fundamentally solve the mildew problem of gypsum board, we must solve the problem of high temperature and humidity, and the most important thing is to solve the problem of high humidity, so as to fundamentally eliminate the conditions for the survival and reproduction of mold. www.sjzjingjin.com