Hydroxypropyl methyl cellulose
Setting time test
The setting time of concrete is mainly related to the setting time of cement, aggregate impact is not big, so the setting time of mortar can be used in place of the study of HPMC for underwater non-dispersion concrete setting time, the influence of mixture due to the setting time by the water-cement ratio of mortar, cement sand ratio effect, so in order to evaluate HPMC influence on mortar setting time, The water-cement ratio and cement-sand ratio of the mortar need to be fixed.
HPMC is a macromolecule linear structure, with hydroxyl group on the functional group, which can form hydrogen bonds with the mixing water molecules and increase the viscosity of the mixing water. HPMC long molecular chains will attract each other, so that HPMC molecules intertwine with each other to form a network structure, the cement, mixing water wrapped. Because HPMC forms a network structure similar to thin film and the wrapping effect of cement, it will effectively prevent the evaporation of moisture in mortar, hinder or slow down the hydration rate of cement.
Water shedding test
The water-bleeding phenomenon of mortar is similar to that of concrete, which will cause serious aggregate settlement, lead to the increase of water-cement ratio of the top layer of slurry, and make the top layer of slurry have great plastic shrinkage or even cracking in the early stage, and the strength of the surface layer of slurry is relatively weak. From the experiment, it can be seen that when the mixing amount is above 0.5%, there is no water leakage phenomenon. This is because when HPMC is mixed into mortar, HPMC has film formation and network structure, as well as the adsorption of hydroxyl on the long chain of macromolecules, so that the cement in mortar and mixing water form flocculation, to ensure the stable structure of mortar body. After adding HPMC in mortar again, many independent tiny bubbles will be formed. These bubbles will be evenly distributed in the mortar and hinder the deposition of aggregate. HPMC the technical performance of cement based materials have a great impact, often used to prepare such as dry mortar, polymer mortar and other new cement based composite materials, so that it has good water retention, plasticity.
Post time: Apr-26-2024