Wet mixed mortar: mixed mortar is a kind of cement, fine aggregate, admixture and water, and according to the properties of various components, according to a certain ratio, after being measured at the mixing station, mixed, transported to the location where the truck is used, and entered into a special Store the container and use the finished wet mixture for the time specified.
Hydroxypropyl methylcellulose is used as a water-retaining agent for cement mortar and retarder for mortar pumping. In the case of gypsum as a binder to improve application and prolong working time, the water retention of HPMC prevents the slurry from cracking too quickly after drying, and improves the strength after hardening. Water retention is an important property of hydroxypropyl methylcellulose HPMC, and it is also a concern of many domestic wet-mix mortar manufacturers. Factors affecting the water retention effect of wet-mixed mortar include the amount of HPMC added, the viscosity of HPMC, the fineness of the particles and the temperature of the use environment.
There are three main functions of hydroxypropyl methylcellulose HPMC in wet-mix mortar, one is excellent water holding capacity, the other is the influence on the consistency and thixotropy of wet-mix mortar, and the third is the interaction with cement . The water retention of cellulose ether depends on the water absorption rate of the base, the composition of the mortar, the thickness of the mortar layer, the water demand of the mortar, and the setting time. The higher the transparency of hydroxypropyl methylcellulose, the better the water retention.
Factors affecting the water retention of wet-mixed mortar include cellulose ether viscosity, addition amount, particle size and temperature. The greater the viscosity of cellulose ether, the better the water retention. Viscosity is an important parameter of HPMC performance. For the same product, the results of using different methods to measure viscosity vary greatly, and some even have a double gap. Therefore, the comparison of viscosity must be carried out in the same test method, including temperature, spindle, etc.
Generally speaking, the higher the viscosity, the better the water retention. However, the higher the viscosity, the higher the molecular weight of HPMC and the lower the solubility of HPMC, which has a negative impact on the strength and construction performance of the mortar. The higher the viscosity, the more obvious the thickening effect of the mortar, but it is not directly related. The higher the viscosity, the more viscous the wet mortar, the better the construction performance, the performance of the viscous scraper and the higher the adhesion to the substrate. However, the increased structural strength of the wet mortar itself does not help. The two constructions have no obvious anti-sag performance. In contrast, some medium and low viscosity but modified hydroxypropyl methylcellulose has excellent performance in improving the structural strength of wet mortar.
The greater the amount of cellulose ether added to PMC wet mortar, the better the water retention, and the higher the viscosity, the better the water retention. Fineness is also an important performance indicator of hydroxypropyl methylcellulose.
The fineness of hydroxypropyl methylcellulose also has a certain influence on its water retention. In general, for hydroxypropyl methylcellulose with the same viscosity and different fineness, the smaller the fineness, the smaller the water retention effect under the same addition amount. the better.
In wet-mixed mortar, the addition amount of cellulose ether HPMC is very low, but it can significantly improve the construction performance of wet mortar, and it is the main additive that mainly affects the performance of mortar. Reasonable selection of hydroxypropyl methylcellulose, the performance of wet mortar is greatly affected.
Post time: Apr-25-2023