Mortar admixtures have poor plasticity, which causes mortar hardly maintains its optimum state. Who can give me some directions about this?

L

Luis

Member
Mortar admixtures have poor plasticity, which causes mortar hardly maintains its optimum state. Who can give me some directions about this?

When the machine has just finished mixing, the overall condition of the mortar looks good. After standing for 2 hours, the mortar began to loosen. I thought it was a problem with the retarder. I added retarder and cellulose ether, but nothing changed.

Besides cellulose ether, what other materials can thicken the viscosity and keep the mortar full? Please give me some advice. Thank you.
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The sand problem is generally considered first, whether it is washed sand or powder content. If the sand is too clean usually causes too fast a loss of air bubbles and less slurry.
 
If there is no problem with the cellulose ether, then think about the aggregate, such as whether the grading is reasonable, the modulus of the sand is too large, and the mud content of the sand is too high. Generally speaking, it is recommended not to add any retarder to ordinary mortar, especially sodium gluconate. The small amount of gelling material has a relatively significant impact on the stability of the slurry.
 
The additives for wet mixing need to add some carboxylic acid, cellulose ether, air-entraining agent, retarder, and sodium gluconate with white sugar is the best. That’s about all I know.
 
Adding an air-entraining agent improves construction and reduces bulk density. The air loss is evident after 2 hours. I have also encountered a similar situation. The cohesion of the mortar may not be good enough. Add some Redispersible Polymer powder and increase the amount of water-reducing agent will improve.
 
Since there is no formula,

Guess 1:

The ratio of powder and aggregate is wrong.

The aggregate grading is terrible.

The cement added less.

The aggregate needs to be fixed.

Guess 2: Used the wrong cellulose ether, or it was fake.

Guess 3: The mixing is uneven, and the water is less.

Guess 4: There are too many other admixtures.

Guess 5: I experienced one time that there was no problem after checking everything. Finally, the problem lies in fly ash. Do you use fly ash?
 
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