The quality difference between high quality glass magnesium air duct and poor quality glass magnesium air duct is very obvious, and the reason is related to the material properties

Magnesium oxychloride cement (Sorel cement, internationally known as Sorel cement) was invented by French scientist Sorel in 1867. It is the second largest inorganic adhesive in the world (the largest is Portland cement). It has good physical properties, 3 times the wear resistance of Portland cement, 1-5 times of impact strength and 3 times of bond strength. There are many multinational construction material companies abroad, For example, Besser company in the United States, Weiler and Vollrath company in Germany, volter Hydra company in Italy and British field company in Japan, etc. all of them produce plates, doors and windows, pipes and movable houses, magnesium oxychloride cement marble, particleboard, fiber pressing board, etc.

The development and application of magnesium oxychloride cement in China began in the early 20th century. In the 1940s, Yingkou and Fushun areas in Northeast China used to make machine-made tiles, floor materials and purlins. However, for a long time, the phase composition, phase structure, strength source and strength influencing factors of the formed magnesium oxychloride cement are not very clear, So that the quality of the products formed by this material has a great degree of blindness and contingency.

The state has invested more than ten million yuan in the Seventh Five Year Plan, and set up the key scientific and technological research project 75-37-04-01 "Research on the physical and chemical basis and characteristics of magnesium cement". A core conclusion is that the stable phase structure of magnesium oxychloride cement is 5.1.8 structure, which lays a foundation for the healthy development of magnesium oxychloride cement in theory. From the late 1980s, this material began to develop rapidly, but it was relatively backward in China, especially for the unscientific and unreasonable ingredients. The strength and phenomenon shown in the early stage were consistent with those of the scientific and standardized components, so it was mistakenly believed that there was no difficulty. However, in the later stage, due to the phase transformation, the performance degradation, re halogenation, frosting, deformation and other phenomena can not be ignored, resulting in the different understanding of the material.

Advantages of high quality glass magnesium materials

① Wear resistance of 3 times that of Portland cement

② 1-5 times the impact strength of Portland cement

③ 3 times the bond strength of Portland cement

Defects and causes of poor quality glass magnesium materials

① Return brine and frost

② Deformation

③ Poor water resistance

When the air humidity is high, there are dew like water drops on the surface of the products, which is commonly known as back brine. In serious cases, it is sticky, flowing and dripping. In a dry environment, there is a white covering on the surface of the air duct, which is commonly known as efflorescence. The physical and mechanical properties of the products (resulting in reduced strength and water-proof and moisture-proof properties) are affected by re halogenation and defrosting, and the decorative properties of the surface and environmental pollution are seriously affected. The reasons for the back brine and frost are not clear about the phase composition and phase structure of hardened magnesium oxychloride cement, the improper ratio of MgO and MgCl2; uneven mixing will also cause local re bittern phenomenon, which is easy to produce deformation; the non-standard molding and maintenance process will lead to the phenomenon of back brine, frost, expansion crack and crispness.

The forms of deformation include shrinkage deformation, thickness and density deviation and warpage caused by structural asymmetry, which cause air duct cracking and affect the building function and use effect. The causes of deformation are excessive water consumption, large tolerance of thickness and density of air duct and asymmetry of structure.

Under X-ray diffraction, the structure of magnesium oxychloride cement is needle like. This structure has the advantages of high strength, but it also has disadvantages, that is, there is a gap between the needles, and water is easy to penetrate into the structure and destroy the structure, which greatly reduces the strength. The wet strength of some products is less than 50%, that is, the strength is less than 50% of dry after soaking in water. This kind of air duct is eroded by water vapor in the air, and its strength decreases rapidly, This is also the inorganic glass fiber reinforced plastic duct just finished when the strength is very high (can stand people), a period of time after the natural rupture of a major reason. Poor water resistance depends on additives.