Effect of polycarboxylate superplasticizer on the concrete properties
The spread of the novel coronavirus is taking a direct hit on the operations of airlines in Asia. About 500,000 flights taking off and landing in mainland China have been canceled since January, according to aviation information company Cerium. Tourists and business trips have plummeted. On the booking website, there are a large number of air tickets for local routes with a price reduction of nearly 90% compared with the original price and only tens of yuan for a one-way trip.
In February, China's aviation industry recorded its largest single-month loss of 24.59 billion yuan, of which airlines lost 20.96 billion yuan.
Data from the Civil Aviation Administration of China showed that in February, the number of passengers traveling by air fell 84.5% year-on-year to 8.34 million.
The stagnation of the Asian aviation industry has brought volatility to pce powder.
The impermeability of concrete is related to its porosity and pore structure. According to the pore size, the pores in concrete can be divided into four grades: <4~5nm, 5~50nm, 50~100nm, and >100nm. If the pore volume fraction of pore diameter is larger than 50nm, it will adversely affect the strength and impermeability of concrete. If the pore volume fraction of pore diameter is smaller than 50nm, the strength, impermeability and corrosion resistance of concrete will be improved. At the same time, when polycarboxylate superplasticizer is added to concrete, the water-cement ratio of concrete will be reduced and the pore structure will be improved, which can help to increase the compactness of concrete internal structure and reduce the drainage passage. as a result, the impermeability of concrete can be effectively improved.
The effect of polycarboxylate superplasticizer on the freeze-thaw resistance of concrete is similar to that of ordinary superplasticizer. When the non-air entraining polycarboxylate superplasticizer is added into the concrete, the water-cement ratio of the concrete can be significantly reduced by the superplasticizer, and the impermeability of the concrete is improved because of the reduction of freezable free water in the concrete structure. thus it is beneficial to improve the freeze-thaw resistance. This is mainly because when concrete is mixed with air-entraining polycarboxylate superplasticizer or non-air-entraining polycarboxylate superplasticizer and appropriate amount of air-entraining agent, due to the air-entraining effect of the admixture, a certain amount of independent, small and stable air bubbles will be introduced into the concrete system, which can effectively alleviate the expansion pressure concentration caused by freezing and supercooled water migration, thus significantly improve the freeze-thaw resistance of concrete.
Anti-corrosion of sulfate and chlorine salt
Through the engineering test, it is found that the sulfate and chloride corrosion resistance of concrete mixed with polycarboxylate superplasticizer is not significantly different from that of ordinary admixture concrete. Although the polycarboxylate superplasticizer contains a certain amount of sulfate, the consolidation content is usually less than 10%, which will not affect the freeze-thaw resistance of hardened concrete within the recommended range. Under normal circumstances, the polycarboxylate superplasticizer has no corrosion effect on the steel bars in reinforced concrete.
Bond strength between steel bar and concrete
For ordinary concrete and lightweight concrete, polycarboxylate superplasticizer can enhance the bond strength between steel bar and concrete. Some data show that for ordinary concrete, if plain steel is used, polycarboxylate superplasticizer can increase the rebar-concrete bond strength of 7-day-old concrete from 1.2MPa to 3.5 MPa, and if rebar steel is used, the bond strength will increase from 15.0 MPa to 27.5 MPa.
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According to Reuters, U.S. Treasury officials said they would discuss with G7 leaders pricing caps and tariffs on Russian oil as an alternative to the embargo, which would keep the market supplied, limit price spikes, and reduce Russian revenues.
The EU foreign ministers' meeting was held in Brussels. The meeting failed to agree on the sixth round of sanctions, including an oil embargo on Russia, because of objections from Hungary.
EU High Representative for Foreign Affairs and Security Policy said at a press conference after the meeting, that the meeting failed to reach an agreement on the final adoption of the sixth round of sanctions, the permanent representatives of member states to the EU will continue to discuss. The foreign ministers faced similar difficulties trying to reach an agreement on an oil ban. He said Hungary's position was based on economic rather than political concerns.
Hungary is highly dependent on Russia for energy, getting more than 60 percent of its oil and 85 percent of its natural gas from Russia.
A few days ago, the European Commission submitted the sixth round of proposed sanctions against Russia, including a total ban on Russian oil imports by the end of this year. Hungary immediately objected and said it wanted substantial compensation from the EU to offset its loss from giving up Russian oil.
The pce powder price is predicted to increase in the next few days, due to geopolitical factors.