The content of chloride ion should be controlled when compounding polycarboxylic acid high performance superplasticizer
The Biden administration plans to ease sanctions on Venezuelan oil to allow more of the country's crude to reach Europe.
The U.S. will allow European companies still operating in Venezuela to immediately transfer more oil to the continent, while allowing Chevron to negotiate a resumption of operations in Venezuela, according to people familiar with the matter. Venezuela's OPPOSITION, which is backed by the United States, is understood to favor the move. Tight global oil supplies have sent crude and fuel costs soaring, threatening to add to already high inflation. Increasing Venezuelan crude exports would help ease supply constraints while also helping to reduce Europe's dependence on Russian energy.
The US has sought to encourage talks between the Venezuelan government and the US-backed opposition to open the way to free and fair elections by extending a limited license held by Chevron to allow the oil company to maintain its operations in Venezuela and negotiate future operations.
The United States reportedly did not extend a permit to Allow Chevron to drill and sell Venezuelan crude, as the company had hoped.
The license extension will allow Chevron to negotiate with State-run Petroleos de Venezuela SA, with which it has a joint venture. Previously, the company could not directly negotiate with any officials sanctioned by the United States. Chevron has been lobbying the United States to allow it to drill for Venezuelan crude and sell it on world markets to help lower energy prices amid the Russia-Ukraine war.
Affected by the ever-changing international situation, the supply and prices of many commodities like the pce powder are still very uncertain.
In order to improve the early strength of concrete, some manufacturers will add triethanolamine, calcium chloride and industrial salt to the superplasticizer, especially in winter or prefabricated component factories and cement products factories that require high early strength.
The chloride salt brought into the admixture will do great harm to the volume stability and durability of concrete, including:
1. The invasion of chloride-based corrosion medium into concrete will reduce the alkalinity of concrete, destroy the passivation film on the surface of steel bar, and there will be a large potential difference in different parts of the surface of steel bar, resulting in electrochemical reaction, forming anode and cathode.
2. The coarse volume expansion of crystal particles precipitated by repeated hydrolysis and crystallization of chloride salt in concrete makes the concrete crack and reduce the durability of concrete.
3. It is generally believed that the amount of chloride in ordinary reinforced concrete will not necessarily rust if the amount of chloride in ordinary reinforced concrete is less than 0.5%. However, when sodium chloride reduces the freezing point of the solution, when the concrete gradually freezes from the outside to the inside, the chloride ion content in the unfrozen solution becomes higher and higher, that is, the chloride ion concentration of the remaining solution will be more than 0.5%, causing local rust. Therefore, in the actual production, although a small amount of chlorine salt may form a higher concentration, corrosion may occur. And sodium chloride and calcium chloride will not enter the molecular structure of hydration products, but exist in a free state in the void, which is easy to absorb moisture and increase the shrinkage of hardened concrete, which is also disadvantageous to the durability.
Effect of alkali content on concrete additives
When the alkali content in cement is high, the effect of superplasticizer is reduced. The setting time is shortened and the early strength is increased. Too high or too low alkali content in cement has an adverse effect on the compatibility of superplasticizer and cement. This may be due to the fact that it changes the solubility of gypsum and thus affects the hydration of C3A. The best soluble alkali content is 0.4%-0.6% (equivalent Na2O). When the adaptability between admixture and cement is serious, some aminosulfonate superplasticizer should be added to replace nano superplasticizer (or polycarboxylic acid system), and the total amount of water reducing components should be appropriately increased to improve the adaptability of the product.
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Europe has been facing the gas shortage problem since the second half of 2021. The worsening situation in Russia and Ukraine has reduced Russian gas shipments to Europe, leading to a doubling of European gas prices. Energy shortages have sent electricity prices soaring. For these reasons, it is predicted that the price of the pce powder will continue to increase.