The superiority and stability of the mechanized construction of plastering mortar are the key factors for the development, and cellulose ether, as the core additive of plastering mortar, plays an irreplaceable role. Cellulose ether has the characteristics of high water retention rate and good wrapping property, and is especially suitable for mechanized construction of plastering mortar.
Water retention rate of plastering mortar
The water retention rate of plastering mortar is an increasing trend when the viscosity of cellulose ether is from 50,000 to 100,000, and it is a decreasing trend when it is from 100,000 to 200,000, while the water retention rate of cellulose ether for machine spraying has reached more than 93%. The higher the water retention rate of the mortar, the less likely the mortar will bleed. During the spraying experiment with a mortar spraying machine, it was found that when the water retention rate of cellulose ether is lower than 92%, the mortar is prone to bleeding after being placed for a period of time, and, at the beginning of spraying, it is particularly easy to block the pipe. Therefore, when preparing plastering mortar suitable for mechanized construction, we should choose cellulose ether with higher water retention rate.
Plastering mortar 2h consistency loss
According to the requirements of GB/T25181-2010 “Ready Mixed Mortar”, the two-hour consistency loss requirement of ordinary plastering mortar is less than 30%. The 2h consistency loss experiment was carried out with viscosities of 50,000, 100,000, 150,000, and 200,000. It can be seen that as the viscosity of cellulose ether increases, the 2h consistency loss value of mortar will gradually decrease. However, during the actual spraying, it was found that during the later leveling treatment, because the viscosity of cellulose ether is too high, the cohesion between the mortar and the trowel will be greater, which is not conducive to construction. Therefore, in the case of ensuring that the mortar does not settle and does not delaminate, the lower the viscosity value of the cellulose ether, the better.
Plastering mortar opening time
After the plastering mortar is sprayed on the wall, due to the water absorption of the wall substrate and the evaporation of moisture on the mortar surface, the mortar will form a certain strength in a short period of time, which will affect the subsequent leveling construction, so it is necessary to analyze the setting time of the mortar. The viscosity value of cellulose ether is in the range of 100,000 to 200,000, the setting time does not change much, and it also has a certain correlation with the water retention rate, that is to say, the higher the water retention rate, the longer the setting time of the mortar.
Fluidity of plastering mortar
The loss of spraying equipment has a lot to do with the fluidity of the plastering mortar. Under the same water-material ratio, the higher the viscosity of cellulose ether, the lower the fluidity value of mortar. That is to say, the higher the viscosity of cellulose ether, the greater the resistance of the mortar and the greater the wear and tear on the equipment. Therefore, for the mechanized construction of plastering mortar, the lower viscosity of cellulose ether is better.
Sag resistance of plastering mortar
After the plastering mortar is sprayed on the wall, if the sag resistance of the mortar is not good, the mortar will sag or even slip off, seriously affecting the flatness of the mortar, which will cause great trouble to the later construction. Therefore, a good mortar must have excellent thixotropy and sag resistance. The experiment found that after the cellulose ether with a viscosity of 50,000 and 100,000 was erected vertically, the tiles directly slid down, while the cellulose ether with a viscosity of 150,000 and 200,000 did not slip. The angle is still vertically erected, and no slippage will occur.
Strength of plastering mortar
Using 50,000, 100,000, 150,000, 200,000, and 250,000 cellulose ethers to prepare plastering mortar samples for mechanized construction, it was found that with the increase of cellulose ether viscosity, the strength value of plastering mortar lower. This is because cellulose ether forms a high-viscosity solution in water, and a large number of stable air bubbles will be introduced during the mixing process of the mortar. After the cement hardens, these air bubbles will form a large number of voids, thereby reducing the strength value of the mortar. Therefore, the plastering mortar suitable for mechanized construction must be able to meet the strength value required by the design, and a suitable cellulose ether must be selected.
The coordination of man-machine material is the key factor of mechanized construction, and the quality of mortar is the most important. Only by using the appropriate cellulose ether can the properties of the mortar meet the needs of machine spraying.
Post time: Jul-21-2023