Recently, covid 19 outbreak spreads in Shanghai, China. There are more than 25,000 new asymptomatic domestic infections every day. China is implementing a dynamic zero-out policy. A leading respiratory expert said the key to COVID-19 prevention and control is to minimize transmission and fatality rate. Omicron has a low case fatality rate but is highly transmissible and can still claim many lives in large outbreaks. "Total openness is not applicable in China. For China, we should keep to the dynamic zero-out and gradually open up."
However, "dynamic zero clearance" is not the pursuit of complete "zero infection". As the Novel Coronavirus has its own uniqueness and strong concealment, there may be no way to prevent the detection of cases at present, but rapid detection and prompt treatment must be carried out, as soon as one case is found, one case will be dealt with.
The situation in Shanghai is serious. As the financial center of China, Shanghai is a very important city, and the outbreak of the epidemic in Shanghai will put a great impact on China's economy. The current task is to contain the spread of the epidemic as soon as possible, to achieve social zero so that Shanghai's life and economy quickly return to normal.
As China plays an important role in the global supply chain, the outbreak will have a significant impact on the supply and prices of many concrete superplasticizer .
Concrete water reducing agent is one of the technical ways to reduce the cement dosage, improve the utilization rate of industrial waste residue, and realize the durability and high performance of concrete. It is also one of the key materials for the development of concrete to high-tech field. And polycarboxylate type water reducing agent (PC) has become a kind of efficient water reducing agent with the most rapid development and the largest market potential because of its low toxicity and environmental protection characteristics. Compared with the traditional admixtures, the admixtures have become the focus of worldwide research and development because of their excellent dispersibility and slump retention ability.
Although polycarboxylate water reducing admixture outstanding performance and ability to maintain good slump has been widely recognized, but because of the existence of mineral composition, cement fineness, cement plaster form and content, admixture adding amount, and the mixing process of concrete mixture ratio, water has a very high sensitivity, seriously affected the existing products are widely used in engineering.
What is Polycarboxylate Series Water Reducing Agent?
Polycarboxylate superplasticizer is a kind of surfactant containing carboxylic graft copolymer. Its molecules are comb shaped and have high steric hindrance effect. As the third generation of high-performance water reducing agent after lignosulfonate ordinary water reducing agent, naphthalene series aliphatic group, sulfamate and other high-efficiency water reducing agent.
It is because of molecular structure design performance is good, high reduce water, low admixture amount, keep slump good, enhance good, contain alkali amount is low, to set time influence is small, and most cement compatibility is good and pollution-free and other advantages are regarded as the most development potential of water reducing agent variety.
Polycarboxylate superplasticizer is a new high-efficiency superplasticizer developed and produced successfully after naphthalene, melamine, aliphatic and sulfamate superplasticizer. In its content is low (solid content 0.15% - 0.25%) can produce an ideal water reducing and enhanced effect, less impact on the setting time of concrete and slump retention, adaptability to cement and admixture is relatively good, a smaller influence on drying shrinkage of concrete (usually not too much increase drying shrinkage), without the use of formaldehyde in the process of production and does not discharge waste liquor, SO The low content of 42- and Cl- has been praised by researchers and some users since the beginning.
Why should Polycarboxylate Superplasticizer be Modified?
Compared with naphthalene series high efficient water reducing agent, such as, although poly carboxylic acid water reducing agent in the reduction of water conservation slump has obvious advantages in aspects of environmental protection, but there are some technical problems in the practical engineering application, such as water reducing effect of concrete raw materials, mixing ratio, water reducing agent dosage dependence is very big, fresh concrete performance is sensitive to water consumption, easy preparation of large liquidity segregation layer. Poor compatibility with other water-reducing agents and modified components and poor product stability greatly restrict the wide application and development of polycarboxylate water-reducing agents.
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, defoamy, 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.
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Twitter recently announced that it had reached an agreement with Musk to take full ownership of the company for $54.20 per share, or about $44 billion in cash. After the deal, Twitter will become a privately held company. The deal, which has been unanimously approved by Twitter's board but still requires shareholder and regulatory approvals, is expected to close in 2022.
After Tesla CEO Elon Musk's acquisition of Twitter was finalized, Twitter founder Jack Dorsey sent out a series of six tweets expressing his expectations for Musk.
Dorsey called Twitter his biggest regret, saying, “The idea and service is all that matters to me, and I will do whatever it takes to protect both. Twitter as a company has always been my sole issue and my biggest regret. It has been owned by Wall Street and the ad model. Taking it back from Wall Street is the correct first step.
"In principle, I don't believe anyone should own or run Twitter," Dorsey goes on. He thinks the service is a public good.
He called Musk a "singular solution" to Twitter's problems, "Elon's goal of creating a platform that is" Maximally trusted and inclusive "is the right one." He wrote, "Thank you both for getting the company out of an impossible situation. This is the right path... I believe it with all my heart."
Besides, because of the ever-changing international situation, the supply and prices of international bulk concrete superplasticizer are still very uncertain.
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