1. Research background of the effect of cellulose ether on plastic free shrinkage of mortar
Mortar is a widely used material in construction projects, and the stability of its performance has a vital impact on the quality of buildings. Plastic free shrinkage is a phenomenon that may occur in mortar before hardening, which will cause problems such as cracks in the mortar, affecting its durability and aesthetics. Cellulose ether, as a commonly used additive in mortar, has an important influence on the plastic free shrinkage of mortar.
2. The principle of cellulose ether reducing plastic free shrinkage of mortar
Cellulose ether has excellent water retention. Water loss in mortar is an important factor leading to plastic free shrinkage. The hydroxyl groups on the cellulose ether molecules and the oxygen atoms on the ether bonds will form hydrogen bonds with water molecules, turning free water into bound water, thereby reducing water loss. For example, in some studies, it was found that with the increase of cellulose ether dosage, the water loss rate in mortar decreased linearly. Like methyl hydroxypropyl cellulose ether (HPMC), when the dosage is 0.1-0.4 (mass fraction), it can reduce the water loss rate of cement mortar by 9-29%.
Cellulose ether improves the rheological properties, porous network structure and osmotic pressure of fresh cement paste, and its film-forming property hinders the diffusion of water. This series of mechanisms jointly reduce the stress generated by moisture changes in the mortar, thereby inhibiting plastic free shrinkage.
3. Effect of cellulose ether dosage on plastic free shrinkage of mortar
Studies have shown that the plastic free shrinkage of cement mortar decreases linearly with the increase of cellulose ether dosage. Taking HPMC as an example, when the dosage is 0.1-0.4 (mass fraction), the plastic free shrinkage of cement mortar can be reduced by 30-50%. This is because as the dosage increases, its water retention effect and other shrinkage inhibition effects continue to increase.
However, the dosage of cellulose ether cannot be increased indefinitely. On the one hand, from an economic point of view, too much addition will increase the cost; on the other hand, too much cellulose ether may have a negative impact on other properties of mortar, such as the strength of mortar.
4. The significance of the influence of cellulose ether on the plastic free shrinkage of mortar
From the perspective of practical engineering application, the reasonable addition of cellulose ether to mortar can effectively reduce the plastic free shrinkage, thereby reducing the occurrence of mortar cracks. This is of great significance for improving the quality of buildings, especially for improving the durability of structures such as walls.
In some special projects with high requirements for mortar quality, such as some high-end residential buildings and large public buildings, by controlling the influence of cellulose ether on the plastic free shrinkage of mortar, it can be ensured that the project meets high quality standards.
5. Research prospects
Although there have been certain research results on the influence of cellulose ether on the plastic free shrinkage of mortar, there are still many aspects that can be explored in depth. For example, the influence mechanism of different types of cellulose ethers on the plastic free shrinkage of mortar when they act together with other additives.
With the continuous development of construction technology, the requirements for mortar performance are also constantly increasing. Further research is needed on how to more accurately control the application of cellulose ether in mortar to achieve the best effect of inhibiting plastic free shrinkage while taking into account other properties of mortar.
Post time: Dec-13-2024