The necessity of water retention
Water retention of mortar
It refers to the ability of the mortar to retain water. Mortar with poor water retention is prone to water segregation during transportation and storage, that is, water floats on the top, and sand and cement sink below. It we have to stir it again before use.
All kinds of construction substrates have a certain degree of water absorption. If the water retention of the mortar is poor, the water in the ready-mixed mortar will be absorbed as soon as the mortar is applied to the block or base layer during the construction. Meanwhile, water on the mortar surface volatilizes into the air, causing the mortar to become insufficient in water due to water loss, affecting the further hydration of the cement. So affects the development of the mortar strength, resulting in strength, especially the interface strength between the hardened body of the mortar and the base layer becoming low, causing the mortar to crack and fall off. However, for mortar with good water retention, the hydration is more complete, its strength can develop normally, and it can bond well with the base layer.
Ready-mixed mortar is usually built between absorbent blocks or applied on the substrate, forming an integral whole with the base. The impact of poor water retention of mortar on project quality is as below,
1) Excessive water loss from the mortar affects the normal coagulation and hardening of the mortar and reduces the bonding strength between the mortar and the surface. This not only makes construction operations inconvenient but also reduces the strength of the masonry, thereby greatly reducing the quality of the project.
2)If the mortar is not bonded well, the water will be easily absorbed by the bricks, causing the mortar to be too dry and thick, and the application will be uneven. During the implementation of the project, it will not only affect the progress but also make the wall prone to cracking due to dry shrinkage. Therefore, increasing the water retention of mortar can not only improve the construction efficiency but also increase strength.
Traditional water retention methods
The traditional solution is to water the substrate in advance, but this cannot ensure that the substrate is evenly moistened. The ideal hydration target of cement mortar is that the cement hydration product will penetrate the substrate along with the process of water absorption by the substrate, forming an effective “key connection” with the base layer, thereby achieving the required bonding strength.
Watering directly onto the surface of the base layer will cause serious discrepancies in the water absorption of the base layer due to differences in temperature, watering time, and watering uniformity. If the base layer absorbs less water, it will continue to absorb the water in the mortar. So there will be not enough water to participate in cement or gypsum hydration which decreases the final strength. If the water absorption capacity of the layer is too large, the water in the mortar will migrate slowly to the base layer, and even a water-rich layer will be formed between the mortar and the base layer, which will also affect the bonding strength.
The advantage of HPMC in water retention
1) HPMC with good water retention property can substantially reduce the loss of water into absorbing substrates, reduce the rate of water volatilization into the air, and ensure more water stays in the mortar to participate in cement or gypsum hydration, increase the final adhesion strength of the dry mortar.
2)The good water retention performance of HPMC can prolong the curing time of mortar. The ample operating time of mortar makes it apply easily.
3)The water retention of cellulose ether will be affected by the ambient temperature. LANDU’s products have consistent water retention in a wide temperature range, even if above 50℃ for Some special grades.
A simple overview.
HPMC has efficient water retention and is an indispensable additive in building construction. HPMC has high quality consistency and excellent water retention performance. Please CONTACT US now for more details!
