Gypsum Mortar Defect：
At present, gypsum mortar building materials as a new type of building materials, with its good thermal insulation, fire prevention, light weight and air humidity regulation, green safety and environmental protection and other basic characteristics, are more and more widely used in modern construction projects.
Due to the use of traditional cement mortar for many years, after a freeze-thaw cycle, a large area of plastering layer often falls off seriously.
Reason analysis:
- The water absorption of gypsum products is very high, which can reach 50% of its own weight. It is difficult to operate when plastering with ordinary cement mortar due to the water absorption of gypsum.
- The strength of cement mortar after solidification is too high ，while the strength of gypsum products is low. It is difficult for them to bond into a solid whole.
- At the same time, due to the difference of expansion coefficient between cement mortar plastering layer and gypsum products, serious cracks, hollows and falls will occur one year after the construction project is put into use.
The formulation proportion :
| Raw Material | Proportion |
| Quartz Sand（0.05-0.5mm） | 50-56% |
| Ordinary Portland Cement | 20-28% |
| Slaked Lime | 8-12% |
| Heavy Calcium Carbonate | 4-6% |
| Hemihydrate gypsum | 4-6% |
| EVA | 1.4-2.0% |
| HPMC | 0.2-0.4% |
| Polypropylene（6mm） | 0.8-1.2% |
The advantages of HPMC can make up for the inadequacy of gypsum’s performance. Put it into a gravity-free mixer according to the above proportion and mix it evenly with clean water in the proportion of 4 : 1.3. It can be used for plastering gypsum building materials with a thickness of 3-5mm.
Advantages of mixed products:
The mixed product is prepared，Because HPMC has good water retention so high bonding strength and good compatibility between thin plaster and gypsum building materials. During construction, it is easy to operate and reduce labor intensity. HPMC has strong adhesion and the surface of plastering layer can be waterproof and adhered to ceramic tiles as usual.
By adding HPMC and other ingredients, a formula suitable for special dry mortar was prepared. This formula solves the problem of plastering gypsum building materials and effectively promotes the application of gypsum building materials in construction projects.