(1) the volume of magnesium cement under natural curing is a continuous expansion process, the linear expansion rate is 0.1~0.2%, and the volume expansion rate is about 1%.

②菱鎂礦在服燒過程中不可避免地產生局部過燒，使一部分MgO呈死燒狀態，過燒的MgO水化過程很慢，當已形成強度的水泥石中的MgO再遇水進行水化時，生成Mg(OH)2，體積膨脹120%;

In the process of burning the magnesite inevitably produces local overheating, which makes a part of MgO in a state of death, and the MgO hydration process of over burning is very slow. When the MgO in the cement stone has been formed, the Mg (OH) 2 is generated and the volume expansion is 120%.

③輕燒氧化鎂中游離CaO水化時體積膨脹90%，而鹵片中存在著 SO42-，當Ca(OH)2轉化成石膏時，固體體積將增加2倍以上，導致制品變形，這也是限制輕燒氧化鎂中游離CaO含量、鹵片中SO42-含量的原因;

(3) the volume expansion of free CaO in light burning Magnesium Oxide is 90%, while SO42- exists in the halogen slices. When Ca (OH) 2 is converted into gypsum, the volume of solid will increase more than 2 times, resulting in the deformation of the products. This is the original cause of limiting the free CaO content in Magnesium Oxide and the content of SO42- in the halogen slices.

④MgO-Mg-C12-H2O系統水化過程是一個強烈的放熱反應過程，而生產的管道體積又大，若環境溫度較高，則反應升溫過程，板材本體溫度過高，反應不充分，造成較大的結晶應力和熱膨脹應力，使制品體積膨脹。

(4) the hydration process of MgO-Mg-C12-H2O system is a strong exothermic reaction process, and the volume of the pipeline is large. If the temperature of the environment is high, the reaction temperature process is high, the temperature of the plate is too high and the reaction is insufficient, resulting in the larger crystallization stress and thermal expansion stress, so that the volume of the product is expanded.