Hydroxypropyl methylcellulose (HPMC) is an organic polymer chemical widely used in building materials, especially in mortars, coatings, adhesives and other products. The main function of HPMC admixture is to improve the construction performance of mortar, improve water retention and extend the opening time. As the demand for high-performance materials in the construction industry continues to increase, the application of HPMC has received widespread attention.
1. Basic properties of HPMC
HPMC is a water-soluble cellulose ether with good hydration, adhesion and thickening properties. It can significantly improve the water retention of mortar, extend the opening time, and enhance the sag resistance and construction operability of mortar. These excellent properties make HPMC one of the common admixtures in mortar and other building materials.
2. Drying process of mortar
The drying process of mortar usually includes two parts: evaporation of water and cement hydration reaction. Cement hydration is the primary mechanism for mortar curing, but evaporation of water during drying also plays an important role. The moisture in the cement mortar needs to be gradually removed through the evaporation process, and the speed of this process directly affects the quality, durability and subsequent construction performance of the finished product after construction.
3. Effect of HPMC on mortar drying speed
The influence of AnxinCel®HPMC admixture on the drying speed of mortar is mainly reflected in two aspects: water retention and water evaporation control.
(1) Improved water retention and slowed down drying speed
HPMC has strong hydration and water retention properties. It can form a hydration film in the mortar to reduce the rapid evaporation of water. The better the water retention of the mortar, the slower it dries because the water is retained in the mortar for a longer period of time. Therefore, after adding HPMC, the evaporation process of water in the mortar will be inhibited to a certain extent, resulting in a prolonged drying time.
Although slowing down the evaporation of water may prolong the drying time of the mortar, this slow drying process is beneficial, especially during the construction process, as it can effectively prevent problems such as surface dryness and mortar cracking and ensure construction quality.
(2) Adjustment of cement hydration process
The role of HPMC in cement mortar is not limited to improving water retention. It can also regulate the hydration process of cement. By changing the rheology of mortar, HPMC can affect the degree of contact between cement particles and moisture, thereby affecting the hydration rate of cement. In some cases, the addition of AnxinCel®HPMC may slightly delay the hydration process of the cement, causing the mortar to cure slower. This effect is usually achieved by adjusting the cement particle size distribution and the contact of cement particles, thereby affecting the drying speed.
(3) Adaptability to environmental humidity
HPMC can improve the evaporation resistance of mortar, making the mortar more adaptable to environmental humidity. In a dry environment, the water retention effect of HPMC is particularly significant. It can effectively delay the loss of surface moisture and reduce surface cracks caused by excessive drying speed. This is especially important in hot or dry environments. Therefore, HPMC not only adjusts the water evaporation rate, but also enhances the adaptability of the mortar to the external environment, indirectly extending the drying time.
4. Factors affecting drying speed
In addition to the addition of HPMC admixture, the drying speed of mortar is also affected by many other factors, including:
Mortar ratio: The ratio of cement to water and the ratio of fine aggregate to coarse aggregate will affect the moisture content of the mortar and thus the drying speed.
Environmental conditions: Temperature, humidity and air circulation conditions are important factors that affect the drying speed of mortar. In an environment of high temperature and low humidity, water evaporates faster, and vice versa.
Mortar thickness: The thickness of mortar directly affects its drying process. Thicker screeds usually take longer to dry completely.
5. Practical application considerations
In practical applications, construction engineers and construction workers often need to balance the drying speed of the mortar with the workability of the construction. As an admixture, HPMC can delay the drying speed, but this feature is very beneficial in environments where construction time needs to be maintained. For example, in high-temperature, air-drying environments, HPMC can effectively prevent surface dryness and cracking, ensuring better operability and longer opening time of the mortar during construction.
However, in some specific cases, such as projects that require fast drying of mortar, it may be necessary to control the amount of HPMC added or choose a formula that does not contain HPMC to speed up the drying process.
As a mortar admixture,AnxinCel® HPMC can effectively improve the water retention of mortar, extend the opening time, and indirectly affect the drying speed of mortar. After adding HPMC, the drying speed of mortar usually slows down, which has a positive effect on avoiding problems such as dry cracking during construction. However, changes in drying speed are also affected by various factors such as mortar ratio and environmental conditions. Therefore, in practical applications, the amount of HPMC must be reasonably selected according to specific conditions to achieve the best construction effect.
Post time: Jan-10-2025