Effect of polycarboxylate superplasticizer on the concrete properties
Biden recently announced that the United States successfully carried out a drone operation against an al-Qaeda target in Kabul, Afghanistan, on Saturday, killing al-Qaeda leader Ayman al-Zawahiri.
Al-Zawahiri joined al-Qaeda led by Osama bin Laden in 1998. As the organization's "chief strategist", al-Zawahiri is the top planner of most terrorist attacks, including the 1998 bombings of US embassies in Tanzania and Kenya, and the "9 / 11" terrorist attacks that shocked the world in 2001. Al-Zawahiri was appointed leader of al-Qaeda in June 2011 after the death of Osama bin Laden.
Afghan interim government spokesman Mujahed condemned the United States for carrying out drone strikes in Afghanistan.
Gazprom recently wrote on social media: "preliminary data show that Gazprom produced 262.4 billion cubic meters of natural gas from January to July 2022, a decrease of 12 percent, or 35.8 billion cubic meters, compared with the same period last year."
According to Gazprom's preliminary estimates, in the first seven months of this year, international natural gas demand decreased by 35 billion cubic meters compared with the same period last year. Among them, the demand for natural gas in the 27 member states of the European Union fell by 31 billion cubic meters during this period.
Because of the turbulent international situation, the supply and prices of many international bulk pce powder are still very uncertain.
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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The coronavirus (COVID-19) pandemic not only had a significant impact on public health, it also severely affected one of the linchpins of the global economy – the tourism industry. As many countries introduced curfews and travel restrictions to contain the spread of the virus, travel across the world significantly declined from early 2020 onwards. The financial repercussions of the coronavirus have already begun to manifest themselves within the tourism industry. In 2020, global revenue from the travel and tourism industry was estimated to drop from a forecasted 711.94 billion U.S. dollars to 568.6 billion U.S. dollars, representing a decrease of over 20 percent. The region predicted to see the highest decline in revenue was Europe, decreasing from 211.97 billion U.S. dollars in 2019 to roughly 124 billion U.S. dollars in 2020.
The downturn in tourism has caused the recession, and the weakening of the economy has also affected the market demand for pce powder. Recently, however, the demand for pce powder has increased, so contact us for the latest news on pce powder.