Lightweight gypsum plaster wall cracking FanJian cause analysis

Compared with cement mortar, light plastering gypsum has the advantages of strong adhesion, smooth surface, good flame retardancy, good thermal insulation, convenient construction and saving construction period. However, good products may not produce good applications. If we do not pay attention to material control and standardized construction, there may be problems such as cracking, hollowing, dusting and alkali recovery after plastering of gypsum mortar. Xinyang Zhongkai company, as a professional supplier of vitrified beads rather than a plastering stone paste manufacturer, shares the causes of such problems with you from the perspective of a third party and from an objective and real point of view:
Reason 1: the raw materials of plastering gypsum are improperly used, and the content of over burned anhydrous gypsum in building gypsum exceeds the standard. However, this part of gypsum does not undergo hydration reaction when encountering water and cannot form bonding, resulting in cracking. The content and proportion of rubber powder and HPMC in the admixture will also affect the adhesion. Vitrified beads as one of the lightweight aggregates, its unreasonable particle gradation will also lead to cracking.
Reason 2: the treatment of the base course is not clean or improper (for example, the base course is too dry, and the loose objects or dust are not removed completely), resulting in the reduction of the adhesion between plastering gypsum and base course materials.
Reason 3: the construction site is subject to mandatory ventilation, and the plastering gypsum has plastic cracking due to rapid drying due to lack of water; The construction site temperature is too low or too high to slow down the solidification time of plastering gypsum. The initial strength of plastering gypsum is low and cannot resist the shrinkage of plastering layer caused by water reduction.
Reason 4: uneven mixing of powder and water; The plastering gypsum is mixed with other materials, resulting in low strength of plastering gypsum; After the wet slurry hardens, add water and stir again.
Reason 5: the concrete wall is bubbling without treatment; The construction thickness of plastering layer is too thick; The matrix joints of different materials have not been strengthened by hanging mesh or reinforcing mesh cloth has not been paved in place as required.
Reason 6: the plastering gypsum contains too much water during the putty construction (the putty will be applied soon after the plastering gypsum construction), and the shrinkage of the putty layer and the plastering layer is inconsistent, resulting in large-area hollowing and falling off.
Reason 7: use cheap expanded perlite instead of vitrified beads as light aggregate, because the expanded perlite has high water absorption and absorbs water in a humid environment. When the environment is dry, these water vapor is easy to bring out gypsum crystals, resulting in alkalization.
In short, the essence of gypsum plastering is the chemical reaction process of calcium sulfate hemihydrate and water to form calcium sulfate dihydrate. The long reaction time (initial setting time), water content, temperature and the contact degree between particles and water are the restrictive conditions for the adequacy of the reaction. Only if these conditions are well controlled, common quality problems such as hollowing, cracking, powdering and alkali returning will not occur.