In cement mortar and gypsum-based slurry, hydroxypropyl methylcellulose mainly plays the role of water retention and thickening, which can effectively improve the cohesion and sag resistance of the slurry. Factors such as air temperature, temperature and wind pressure will affect the evaporation rate of water in cement mortar and gypsum-based products. Therefore, in different seasons, there are some differences in the water retention effect of products with the same amount of hydroxypropyl methylcellulose added. In the specific construction, the water retention effect of the slurry can be adjusted by increasing or decreasing the amount of HPMC added. The water retention of methyl cellulose ether at high temperature is an important indicator to distinguish the quality of methyl cellulose ether.
Excellent hydroxypropyl methylcellulose series products can effectively solve the problem of water retention at high temperature. In high temperature seasons, especially in hot and dry areas and thin-layer construction on the sunny side, high-quality HPMC is required to improve the water retention of the slurry.
High-quality HPMC, with very good uniformity, its methoxy and hydroxypropoxy groups are evenly distributed along the cellulose molecular chain, which can improve the ability of the oxygen atoms on the hydroxyl and ether bonds to associate with water to form hydrogen bonds , so that free water becomes bound water, so as to effectively control the evaporation of water caused by high temperature weather and achieve high water retention. Water is required for hydration in order to set cementitious materials such as cement and gypsum. The correct amount of HPMC can keep the water in the mortar long enough to allow the setting and hardening process to continue.
The amount of HPMC required to obtain sufficient water retention capacity depends on:
1. The absorbency of the base layer
2. The composition of mortar
3. The thickness of the mortar
4. Water requirement of mortar
5. The setting time of the cementitious material
High-quality hydroxypropyl methylcellulose can be uniformly and effectively dispersed in cement mortar and gypsum-based products, and wraps all solid particles, and forms a wetting film, and the moisture in the base is gradually released for a long time. , and the hydration reaction occurs with the inorganic cementitious material, thereby ensuring the bonding strength and compressive strength of the material.
Therefore, in high-temperature summer construction, in order to achieve the effect of water retention, it is necessary to add high-quality HPMC products in sufficient quantities according to the formula, otherwise, there will be insufficient hydration, strength reduction, cracking, hollowing and falling off caused by too fast drying. It also increases the difficulty of construction for workers. As the temperature decreases, the addition amount of HPMC can be gradually reduced, and the same water retention effect can be achieved.
Post time: Oct-20-2022