Main properties of building plastering

　　(1)凝結硬化快。施工抹灰與水混合后，料漿在幾分鐘內開始喪失塑性，30分鐘內完全喪失塑性并產生強度，一周左右完全變硬。為滿足施工要求，加入硼砂、酒石酸鉀鈉、檸檬酸、聚乙烯醇、石灰活性骨膠或皮膚膠等緩凝劑。

　　(1) Fast coagulation and hardening. After mixing with water, the slurry begins to lose plasticity in a few minutes, loses plasticity and produces strength completely in 30 minutes, and hardens completely in a week or so. In order to meet the construction requirements, some retarders such as borax, potassium sodium tartrate, citric acid, polyvinyl alcohol, lime active bone glue or skin glue were added.

　　(2)凝固硬化時體積膨脹。石膏膏體在凝固硬化初期會有輕微的膨脹。這一特性石膏制品表面光滑、細膩、尺寸準確、形狀飽滿、裝飾性好。

　　(2) Volume expansion during solidification and hardening. Gypsum will expand slightly at the beginning of solidification and hardening. This characteristic gypsum products have smooth surface, delicate, accurate size, full shape and good decoration.

　　(3)高孔隙度。建筑石膏混合時,有可塑性的建設的要求使漿體,需要加入石膏消費的用水量60% ~,和建筑石膏水化的理論水需求是18.6%,所以,當大量的自由水蒸發,形成大量的毛細孔隙內建筑石膏產品。導熱系數小，吸聲性好，屬于輕質保溫材料。

　　(3) High porosity. When building gypsum is mixed, there is a requirement of plasticity, which makes the slurry need to add 60% of the water consumed by gypsum, and the theoretical water demand of building gypsum hydration is 18.6%. Therefore, when a large amount of free water evaporates, a large number of building gypsum products in capillary pore are formed. Low thermal conductivity, good sound absorption, belongs to light insulation materials.

　　(4)具有一定的濕度。由于石膏制品內部大量的毛氣孔間隙對空氣中的蒸汽具有較強的吸附能力，所以對室內空氣濕度具有一定的調節作用。

　　(4) It has a certain humidity. Because a large number of pore gaps in gypsum products have strong adsorption capacity for vapor in the air, it has a certain role in regulating indoor air humidity.

　　(5)防火性能好。石膏制品在發生火災時，將水與水分離，吸收熱量蒸發，并在制品表面形成蒸汽幕并使隔熱層脫水，可有效降低火焰對內部結構的破壞。建筑石膏制品在防火的同時自身也會受到損傷，而石膏制品也不宜長期使用在接近65℃以上高溫的地方，以免2水石膏在此溫度以下失去結晶水，從而失去強度。

　　(5) Good fire protection performance. In case of fire, water and water are separated, heat is absorbed and evaporated, and steam curtain is formed on the surface of gypsum products and the insulation layer is dehydrated, which can effectively reduce the damage of flame to the internal structure. Building gypsum products will be damaged while they are fireproof, and gypsum products should not be used in high temperature areas near 65 C for a long time, so as to avoid the loss of crystalline water and strength of 2-hydrate gypsum below this temperature.

　　(6)耐水性、抗凍性差。建筑石膏硬化體吸濕性強，吸收的水分會削弱石膏顆粒間的結合力，從而顯著降低強度。如果長期浸泡，還會由于二水石膏晶體的逐漸溶解而導致破壞。石膏制品經冷凍吸水飽和后，會因孔隙中水晶體的膨脹而破壞。因此，石膏制品的耐水性和抗凍性較差，不適合潮濕部位使用。為了提高其耐水性，可以加入適量的水泥、礦渣等水力材料，以及機械防水劑等，可以改善石膏制品的孔隙狀態或使孔隙壁增水。

　　(6) Poor water and frost resistance. The building gypsum hardened body has strong hygroscopicity, and the absorbed water will weaken the bonding force between the gypsum particles, thus significantly reducing the strength. If immersed for a long time, it will be destroyed by the gradual dissolution of dihydrate gypsum crystal. When the gypsum products are saturated by freezing and water absorption, they will be destroyed by the expansion of crystal in the pore. Therefore, the water resistance and freezing resistance of gypsum products are poor, and they are not suitable for use in wet parts. In order to improve its water resistance, some hydraulic materials such as cement, slag and mechanical waterproofing agent can be added to improve the pore state of gypsum products or increase the water content of pore walls.