Action Mechanism of Common Retarders

The European Commission has submitted to member states a new draft of sanctions against Russia, including an oil embargo. Some member states that rely heavily on Russian energy sought exemptions.  

Western media reported that the European Commission draft of the sixth round of sanctions against Russia includes within six to eight months gradually banning oil imports from Russia, but allowing Hungary and Slovakia to extend the transition period for several months; The Russian Savings bank and other large financial institutions on the sanctions list.  

The European Union has imported 44 billion euros of fossil fuels from Russia since Russia launched its special military operation against Ukraine in late February, according to Finland's Energy and Clean Air Research Center.  

The Institute for European and Global Economics in Brussels estimates that the European Union currently consumes about $450 million worth of Russian oil a day.  

Among EU members, landlocked Hungary and Slovakia, which import most of their oil from Russia, cannot quickly find alternative supplies.  Slovakia says the transition will take years.  Some officials believe Bulgaria and the Czech Republic may also seek to opt out of oil sanctions against Russia.

Affected by the ever-changing international situation, the supply and prices of international bulk concrete foaming agent are still very uncertain.

Action principle of retarders

1. Reduce the solubility of hemihydrate gypsum.

2. Slow down the dissolution rate of hemihydrate gypsum.

3. Retarding ions are adsorbed on the surface of dihydrate gypsum crystal, and these ions are combined into the lattice.

4. Form a complex to restrict the diffusion of ions near the dihydrate gypsum crystal.

 

Common retarders

1. Organic acids and their soluble salts: citric acid, tartaric acid, malic acid, etc.

2. Alkaline phosphate: sodium tripolyphosphate.

3. Proteins: bone glue, degraded proteins, polymerized amino acids.

4. Compounding of various retarders.

 

Retarding mechanism of citric acid

Citric acid is a ternary organic acid containing hydroxyl group, which ionizes H + and many kinds of acid ions under different conditions, which form different stable precipitates with calcium. Among them, the stability of the complex is the highest when the PH value is 8.5, so the setting time is the longest.

 

Retarding mechanism of sodium polyphosphate.

Sodium polyphosphate is a straight-chain trimer, which combines with calcium ions in the liquid phase to form insoluble calcium phosphate covering the surface of hemihydrate gypsum, which hinders its dissolution, thus greatly reducing supersaturation and reducing the nucleation probability of dihydrate gypsum crystal.

At the same time, the adsorption of sodium tripolyphosphate on the crystal nucleus surface of dihydrate gypsum reduces the surface energy of the crystal nucleus, increases the nucleation barrier, and prolongs the time for the crystal nucleus to reach the critical nucleation size, which is macroscopically characterized by the prolongation of the induction period and setting time of gypsum.

 

Retarding mechanism of proteins

It is found that macromolecular retarders (proteins) are mixed into gypsum-based materials, combine with calcium ions on the surface of dihydrate gypsum, cover the crystal nucleus surface of dihydrate gypsum, and reduce the crystal nucleus surface can inhibit the growth of crystal nucleus.

At the same time, due to the adsorption and protection of protein colloid, protein colloid inhibits the crystal growth of gypsum, but does not change the crystal morphology, and has little effect on the strength of gypsum.

 

Summary

1. Under the same dosage, the retarding effect of citric acid is the strongest. When the content is more than 0.2%, the retarding time suddenly increases sharply, and when the dosage is 0.3%, the retarding time reaches more than 8 hours, which almost achieves the effect of preventing gypsum from setting.

2. The content of sodium polyphosphate is 0.1%, and the retarding effect is relatively not obvious, and then the time increases suddenly with the increase of the amount of polyphosphate, which is difficult to control when in use.

3. There is a linear relationship between the retarding time and the content of protein retarders, which is beneficial to the operation control.

 

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Greece will hand over Iranian oil it intercepted from a Russian-flagged tanker to the United States at the request of the U.S. Justice Department, Greek port police said recently, AFP reported. The decision angered Tehran.  

In April, Greek authorities reportedly seized a Russian oil tanker, the Pegas, which was said to be heading to the Turkish port of Marmara.  

Reports say the ship was docked in Calistos Bay with a crew of several people said to be Russian. The Greek coast guard said the ship had been renamed the Lana.  

The report notes that the European Union imposed sanctions on Russia after the conflict broke out in February. Greek authorities seized the tanker in accordance with European Union sanctions.  

According to information at the time, the tanker was carrying 115,000 tons of Iranian oil.  

Iran's Ports and Maritime Organization strongly protested Greece's decision, calling it an "international bandit." "The Islamic Republic of Iran will not give up its legitimate rights and expects the Greek government to abide by its international obligations in the area of navigation and shipping," it said in a statement on its website.  

Iran's Foreign Ministry, through the International Maritime Organization, called on the Greek government to release the tanker and its crew overnight, adding that "the Americans discharged their cargo," the report said.  

Athens did not immediately respond to the Iranian protest and gave no further details about the oil on board or how it was handed over to the United States, the report said.

The concrete foaming agent price is expected to increase in the next few days affected by the change in supply and demand markets.

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