The setting time of dry-mixed mortar in the national standard is 3-8 hours, but the setting time of many dry-mixed mortars is unstable. Some mortars set for a long time and do not solidify for a long time. But it is prone to cracking in the later stage. So why is dry-mixed mortar prone to unstable setting time?

Reasons for the long setting time of dry-mixed mortar: First, it may be due to changes in seasons and weather, such as lower temperatures, rainy weather, and humid air, which cause the mortar to not condense for a long time. The second reason may be that the additive amount of hydroxypropyl methylcellulose is too much. Hydroxypropyl methylcellulose has a strong water retention effect. If the amount of hydroxypropyl methylcellulose is too much, the moisture in the mortar will There will be more. As a result, the mortar will not condense for a long time, which will affect the construction operation.

Reasons for the short setting time of dry-mixed mortar: The first is the weather factor, the weather is hot, the temperature is high, and the evaporation is fast. The second is environmental factors, the base material is dry, and no water was sprayed before construction. The third is the low water retention rate of the admixture hydroxypropyl methylcellulose, or the small amount of addition leads to poor water retention of the mortar.

Prevention and control measures: First, the quality of the admixture hydroxypropyl methylcellulose must be strictly tested, cellulose with good water retention should be used and the amount of the admixture should be strictly controlled. It is necessary to adjust the amount of cellulose added according to different seasons, different weather, and different wall materials. The second is to strengthen on-site inspections to keep abreast of construction information.