膏粉是装修中不可或缺的材料，但很多人不知道：同样是石膏粉，凝固时间可以从5分钟到30分钟不等。选错凝固时间，要么来不及施工，要么等得耽误工期。

Plaster powder is an indispensable material in decoration, but many people do not know that gypsum powder can have a solidification time ranging from 5 minutes to 30 minutes. Choosing the wrong solidification time either leaves no time for construction or delays the project timeline.

石膏粉从哪来？ 天然石膏（生石膏，CaSO?·2H?O）经过煅烧、磨细，就得到了建筑石膏（熟石膏，β-CaSO?·1/2H?O）。建筑石膏的主要成分是β型半水石膏。石膏粉按理化性质分为生石膏粉和熟石膏粉；按用途分为建筑石膏、高强石膏、模型石膏、医用石膏等。

Where does gypsum powder come from? Natural gypsum (raw gypsum, CaSO? ·2H? O) is calcined and finely ground to obtain building gypsum (gypsum, β - CaSO?)? ·1/2H? O). The main component of building gypsum is β - type hemihydrate gypsum. Gypsum powder is divided into raw gypsum powder and mature gypsum powder according to its physical and chemical properties; Classified by purpose, it is divided into building gypsum, high-strength gypsum, model gypsum, medical gypsum, etc.

凝结时间的国家标准：根据GB/T 9776标准，建筑石膏的初凝时间要求≥3分钟，终凝时间≤30分钟。实际操作中，建筑石膏的初凝时间通常在5-15分钟，终凝时间在15-30分钟。这意味着：从加水搅拌到开始凝固，你只有几分钟的操作窗口。

National standard for setting time: According to GB/T 9776 standard, the initial setting time of building gypsum is required to be ≥ 3 minutes, and the final setting time is required to be ≤ 30 minutes. In practical operation, the initial setting time of building gypsum is usually 5-15 minutes, and the final setting time is 15-30 minutes. This means that from adding water and stirring to starting to solidify, you only have a few minutes of operation window.

影响凝结速度的3个因素：

Three factors that affect condensation speed:

煅烧温度：煅烧温度不同，得到的石膏类型不同。190°C左右得到模型石膏，凝结更快、强度更高。

Calcination temperature: Different calcination temperatures result in different types of gypsum. The model gypsum is obtained at around 190 ° C, which sets faster and has higher strength.

细度：石膏粉越细，与水接触面积越大，凝结越快。特硬白石膏细度约1100目，建筑石膏约300目。

Fineness: The finer the gypsum powder, the larger the contact area with water, and the faster it sets. The fineness of ultra hard white gypsum is about 1100 mesh, and that of building gypsum is about 300 mesh.

外加剂：缓凝剂可以延长凝结时间，满足特殊施工需求。

Admixtures: retarders can extend the setting time and meet special construction requirements.

不同用途对凝结时间的要求：

Requirements for setting time for different purposes:

嵌缝石膏：需要较长的操作时间，通常添加缓凝剂，凝结时间控制在20-30分钟。

Jointing gypsum: requires a long operating time, usually with the addition of a retarder, and the setting time is controlled at 20-30 minutes.

石膏板生产：需要快速凝固定型，初凝时间控制在5-8分钟。

Gypsum board production: requires rapid solidification and shaping, with an initial setting time controlled within 5-8 minutes.

装饰线条制作：介于两者之间，需要足够的操作时间又不能太慢。

Decorative line production: Between the two, it requires sufficient operation time and cannot be too slow.

选购建议：买石膏粉时问清楚凝结时间。大面积抹灰选凝结时间稍长的（20-30分钟），小面积修补选凝结快的（5-10分钟）。千万别买回来才发现——还没抹完就已经硬了。

Suggestion for purchasing: When buying gypsum powder, ask for the setting time clearly. For large-scale plastering, choose those with slightly longer setting time (20-30 minutes), and for small-scale repairs, choose those with faster setting time (5-10 minutes). Don't just buy it and realize that it's already hard before you finish wiping it.

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