The US Commerce Secretary has announced that the US will temporarily lift tariffs imposed on Ukraine during the Trump administration to help Ukraine recover its economy and continue to show support for the Russia-Ukraine situation. "For steel mills to remain an economic lifeline for the Ukrainian people, they must be able to export steel," the Commerce Department said in a statement.
The Biden administration will announce the lifting of steel tariffs on Ukraine for one year. Ukraine is a fairly small supplier of U.S. steel, shipping about 218,000 tons in 2019, ranking it 12th among foreign suppliers to the United States, the report said. The U.S. Commerce Department noted that the steel industry is uniquely important to Ukraine's economic strength, with one in 13 people employed in the steel industry.
Affected by the ever-changing international situation, the supply and prices of international bulk polycarboxylate superplasticizer are still very uncertain.
In order to overcome the technical defects in the application of polycarboxylate water-reducing agent, or to improve some or some properties of concrete (workability, slump retention, reduction of bleeding, improvement of early strength, low shrinkage, etc.), it is necessary to modify the concrete.
In practice, the commonly used modification methods include synthetic technology and compound technology. Compared with the synthetic process, the compound method has the advantages of simple operation and low cost, so it is widely used in practical applications. Polycarboxylate series compound technology, is the Polycarboxylate series water-reducing agent and other components (such as slow coagulation, defoaming, air induction, early strength, and other components) according to a certain proportion of the combination compound, in order to achieve the coordination of the superposition of each component.
Compound Polycarboxylate Superplasticizer with Defoaming Air-entraining Component
Polycarboxylate superplasticizer has high surface activity and good foam retention, which will affect the strength of concrete due to excessive gas content. Therefore, in actual use, according to the requirements of construction and use, foam components are selected to reduce the gas content. In addition, air entrainment components are sometimes added to ensure the small stability and uniformity of the internal foam of concrete, so as to meet the performance of concrete.
Polycarboxylate series water reducing agent with defoaming agent
He studied the compound effect of oil-type, emulsified type, dissolved type, and solid defoaming agent with polycarboxylate series water-reducing agent. The results showed that dissolved defoaming agents had good compatibility with polycarboxylate series and could compound pumping agents with high flow, high slump, and high strength. If the storage time is short, emulsified type can also be used; And other kinds of defoaming agent should not be mixed, can only be used.
Polycarboxylate series water reducing agent with defoaming agent and air-entraining agent
Zhang studied the compound technology of defoaming agent, entraining agent and Polycarboxylate superplasticizer, and optimized the compound superplasticizer system that met the requirements of plain concrete. The key to compounding technology is the dosage of defoaming agents and air-entraining agents. By selecting the dosage of defoaming agent and air-entraining agent, the performance requirements of improving workability, increasing strength, increasing compactness, and reducing foaming can be achieved.
Polycarboxylate series water reducing agent with defoaming agent, air-entraining agent, and retarder
Zhang used the compound technology of Polycarboxylate water-reducing agent, defoaming agent, air entrainment agent, and retarder to achieve the synergistic superposition effect of the composite system on workability, slump retention, and setting time of concrete by adjusting the dosage of each component. It is found that foaming can be effectively eliminated and strength improved when the dosage of defoaming agent is controlled at 0.2% of Polycarboxylate superplasmer, cave-retaining property can be significantly improved when the dosage of air-entraining agent is controlled at 0.3% of Polycarboxylate superplasmer, and the effect is better when the retarder (sodium gluconate) is 0.4% of Polycarboxylate superplasmer.
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The current international situation is highly uncertain, and its economic impact has not been able to be assessed properly. In addition, rising energy and commodity prices and supply chain disruptions are expected to push the price of the polycarboxylate superplasticizer higher.
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