In ready-mixed mortar, the addition of cellulose ether is very low, but it can significantly improve the performance of wet mortar, which is a major additive affecting the construction performance of mortar. the important role of HPMC in mortar is mainly in three aspects, one is the excellent water retention capacity, the second is the effect on mortar consistency, and the third is the interaction with cement.
1. The greater the viscosity of cellulose ether, the better the water retention performance.
2. The larger the addition amount of cellulose ether in mortar, the better the water retention performance.
3. For particle size, the finer the particle, the better the water retention.
4. The water retention of methyl cellulose ether decreases with the increase of temperature.
The thickening effect of hydroxypropyl methyl cellulose as a thickener is related to the particle size, viscosity and modification of hydroxypropyl methyl cellulose. Generally speaking, the higher the viscosity of cellulose ether, the smaller the particle size, the more obvious the thickening effect.
The third role of cellulose ethers is to retard the hydration process of the cement. Cellulose ethers give mortar various beneficial properties and also reduce the early hydration heat release of cement and retard the hydration power process of cement. The higher the concentration of cellulose ether in the mineral gel material, the more obvious the effect of delayed hydration. Cellulose ethers not only retard the setting, but also delay the hardening process of cement mortar systems. With the increase of HPMC dosing, the setting time of mortar increased significantly.
In summary, in ready-mixed mortar, HPMC plays the role of water retention, thickening, delaying the hydration power of cement and improving construction performance. The good water retention ability makes the cement hydration more complete, which can improve the wet adhesion of wet mortar and increase the bond strength of mortar. Therefore, HPMC is being widely used as an important additive in ready-mixed mortar.