Main properties of building plastering

　　(1)凝结硬化快。施工抹灰与水混合后，料浆在几分钟内开始丧失塑性，30分钟内完全丧失塑性并产生强度，一周左右完全变硬。为满足施工要求，加入硼砂、酒石酸钾钠、柠檬酸、聚乙烯醇、石灰活性骨胶或皮肤胶等缓凝剂。

　　(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)凝固硬化时体积膨胀。石膏膏体在凝固硬化初期会有轻微的膨胀。这一特性石膏制品表面光滑、细腻、尺寸准确、形状饱满、装饰性好。

　　(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。建筑石膏混合时,有可塑性的建设的要求使浆体,需要加入石膏消费的用水量60% ~,和建筑石膏水化的理论水需求是18.6%,所以,当大量的自由水蒸发,形成大量的毛细孔隙内建筑石膏产品。导热系数小，吸声性好，属于轻质保温材料。

　　(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)具有一定的湿度。由于石膏制品内部大量的毛气孔间隙对空气中的蒸汽具有较强的吸附能力，所以对室内空气湿度具有一定的调节作用。

　　(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。石膏制品在发生火灾时，将水与水分离，吸收热量蒸发，并在制品表面形成蒸汽幕并使隔热层脱水，可有效降低火焰对内部结构的破坏。建筑石膏制品在防火的同时自身也会受到损伤，而石膏制品也不宜长期使用在接近65℃以上高温的地方，以免2水石膏在此温度以下失去结晶水，从而失去强度。

　　(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、抗冻性差。建筑石膏硬化体吸湿性强，吸收的水分会削弱石膏颗粒间的结合力，从而显著降低强度。如果长期浸泡，还会由于二水石膏晶体的逐渐溶解而导致破坏。石膏制品经冷冻吸水饱和后，会因孔隙中水晶体的膨胀而破坏。因此，石膏制品的耐水性和抗冻性较差，不适合潮湿部位使用。为了提高其耐水性，可以加入适量的水泥、矿渣等水力材料，以及机械防水剂等，可以改善石膏制品的孔隙状态或使孔隙壁增水。

　　(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.