The function of cellulose ether in mortar

Cellulose ether water retention

Water retention of mortar refers to the ability of mortar to hold and lock water. The higher the viscosity of cellulose ether, the better the water retention. Because cellulose structure contains hydroxyl and ether bond, hydroxyl and ether bond group of oxygen atoms and water molecules to synthesize hydrogen bond, so that free water into binding water, winding water, so as to play a role of water retention.


Solubility of cellulose ether

1. The coarser cellulose ether is easy to disperse in water without agglomerating, but the dissolution rate is very slow. Cellulose ether below 60 mesh is dissolved in water for about 60 minutes.

2. Fine particles of cellulose ether in water is easy to disperse and not agglomerate, and the dissolution rate is moderate. Cellulose ether over 80 mesh dissolved in water for about 3 minutes.

3. Ultrafine cellulose ether disperses quickly in water, dissolves quickly and forms a fast viscosity. Cellulose ether above 120 mesh is dissolved in water for about 10-30 seconds.


The finer the cellulose ether particles, the better the water retention, coarse particles of cellulose ether and water contact surface immediately dissolved and formed gel phenomenon. The glue wraps the material to prevent the water molecules from continuing to penetrate. Sometimes, even if stirred for a long time, the solution can not be evenly dispersed and dissolved, forming a muddy flocculent solution or agglomerate. Fine particles disperse and dissolve immediately upon contact with water to form a uniform viscosity.


PH value of cellulose ether (delayed coagulation or early strength)

The PH value of cellulose ether manufacturers at home and abroad is basically controlled at about 7, which is acidic. Because there are still a lot of dehydrated glucose ring structure in the molecular structure of cellulose ether, dehydrated glucose ring is the main group that causes cement delay. Dehydrated glucose ring can make calcium ions in cement hydration solution form sugar calcium molecular compounds, reduce the calcium ion concentration in cement hydration induction period, prevent the formation and precipitation of calcium hydroxide and calcium salt crystals, thus delaying the process of cement hydration. If PH value becomes alkaline state, mortar will appear early strength state. Now most of the factories to adjust PH value using sodium carbonate, sodium carbonate is a kind of accelerating agent, sodium carbonate can improve the performance of cement particle surface, prompting cohesion between particles increase, further improve the viscosity of slurry, mortar and sodium carbonate and calcium ion compound rapidly, prompted the formation of ettringite, cement condensation quickly. Therefore, the PH value should be adjusted according to the different customers in the actual production process.


Cellulose ether gas induction

The air entraining of cellulose ether is mainly because cellulose ether is also a surfactant, the interface activity of cellulose ether mainly occurs in the gas-liquid-solid interface, the first is the introduction of bubbles, followed by dispersion and wetting. Cellulose ether contains alkyl group, significantly reduce the surface tension and interfacial energy of water, water solution in the process of agitation is easy to produce many small closed bubbles.


Gelation of cellulose ether

Cellulose ether dissolved in mortar because of its molecular chain of methoxy and hydroxypropyl group in the slurry with calcium ions and aluminum ions in the formation of viscous gel and filled in cement mortar gap, improve the density of mortar, play a role of flexible filling and reinforcement. However, when the composite matrix is pressed, the polymer can not play a rigid support, so the strength and compression ratio of mortar decrease.


Film formation of cellulose ether

A thin latex film is formed between cellulose ether and cement particles after hydration. The film has sealing effect and improves the surface dry phenomenon of mortar. Because the cellulose ether has good water retention, maintain enough water molecules in the interior of the mortar, thus ensuring the strength of the cement hydration and hardening and completely development, improve the bonding strength of mortar, at the same time improve the adhesiveness of cement mortar, the mortar has good plasticity and toughness, reduce mortar contraction deformation.

Post time: Jun-14-2022