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 c…
If the compatibility of polycarboxylate superplasticizer and cement is not good, the concrete mixture is prone to some problems, such as segregation, bleeding, greater slump loss, shorter setting time and so on, so that the concrete mixture can not b…
Under the spread of the new crown epidemic, after Americans experienced life and death, they set off the largest "resignation wave" in history, and the number of resignations broke the highest record since statistics began in 2000. Since April this y…