The Importance of Water Retention of HPMC
April 24th 2024
Importance of HPMC cellulose for water retention of mortar
The need for water retention
The water retention of mortar refers to the ability of mortar to retain water. Mortar with poor water retention is prone to bleeding and segregation during transportation and storage, that is, the water floats on the top, and the sand and cement sink below. It must be re-stirred before use.
All kinds of bases that need mortar for construction have a certain degree of water absorption. If the water retention of the mortar is poor, in the process of mortar application, as long as the ready-mixed mortar is in contact with the block or base, the ready-mixed mortar will be absorbed. At the same time, the surface of the mortar evaporates water from the atmosphere, resulting in insufficient moisture of the mortar due to water loss, affecting the further hydration of the cement, and affecting the normal development of the strength of the mortar, resulting in the strength, especially the interface strength between the hardened body of the mortar and the base layer. becomes lower, causing the mortar to crack and fall off. For mortar with good water retention, the cement hydration is relatively sufficient, the strength can be developed normally, and it can be well bonded with the base layer.
Ready-mixed mortar is usually built between water-absorbing blocks or spread on the base, forming a whole with the base. The impact of poor water retention of mortar on project quality is as follows:
1. Due to the excessive water loss of the mortar, the normal setting and hardening of the mortar is affected, and the adhesion between the mortar and the surface is reduced, which is not only inconvenient for construction operations, but also reduces the strength of the masonry, thereby greatly reducing the quality of the project.
2. If the mortar is poorly bonded, the water will be easily absorbed by the bricks, making the mortar too dry and thick, and the application will be uneven. In the implementation engineer, it will not only affect the progress, but also make the wall easy to crack due to shrinkage;
Therefore, increasing the water retention of the mortar is not only conducive to construction, but also increases the strength.
2. Traditional water retention methods
The traditional solution is to water the base layer, but it is impossible to ensure that the base layer is evenly moistened in the right amount. The ideal hydration goal of cement mortar on the base is: the cement hydration product penetrates into the base along with the process of absorbing moisture from the base to form an effective “key connection” with the base, so as to achieve the required bond strength.
Watering directly on the surface of the base layer will seriously disperse the water absorption of the base layer due to differences in temperature, watering time, and watering uniformity. The base layer has less water absorption and will continue to absorb the water in the mortar. Before the cement hydration, the water is sucked away, which affects the penetration of cement hydration and hydration products into the substrate; the base layer has a large water absorption, and the water in the mortar migrates to the base Slowly, even a water-rich layer is formed between the mortar and the substrate, which also affects the bond strength. Therefore, using the common base watering method not only cannot effectively solve the problem of high water absorption of the wall base, but also affects the bonding strength of the mortar and the base, resulting in hollowing and dry cracking.
3. The role of efficient water retention
The high water retention properties of mortar have several advantages:
1. The excellent water retention performance makes the mortar open longer, and has the advantages of large-scale construction, long use time in the barrel, batch mixing and batch use, etc.
2. Good water retention can fully hydrate the cement in the mortar and effectively improve the bonding performance of the mortar.
3. The mortar has excellent water retention, which makes the mortar less prone to segregation and bleeding. Now, the workability and workability of the mortar are improved.
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