Why is polycarboxylate superplasticizer more suitable for modern concrete?
John Albanese, leader of the Australian Labor Party, was sworn in as Australia's new prime minister. After his victory, Albanese said he would "make a big change" in the country's climate policy.
"We now have an opportunity to end the 'climate wars' in Australia," he said. "Australian businesses understand that doing the right thing on climate is good for our economy and good for jobs, and I hope Australia will join the global effort on climate change," Albanese said Australia would engage with other countries to change policies when it came to tackling climate change.
In addition, Albanese’s Labor Party has proposed a more ambitious plan to cut emissions by 43 percent from 2005 levels by 2030, the report said. However, Labor is not currently planning to phase out coal use or halt new coal mining projects.
The climate issue was a major concern of voters in Australia's general election. Mr. Morrison, the former prime minister, was criticized for failing to direct the response to repeated bushfires in 2019 and 2020.
SBS has reported that According to the latest Climate Change Performance Index of 64 countries released at the 2021 United Nations Climate Change Conference (COP26), Australia's climate policy ranks at the bottom of all countries, and is one of the world's worst performers in three aspects of emissions, renewable energy, and energy use. Australia ranks 52nd in renewable energy, 54th in energy use, and 56th in emissions.
It is predicted that the prices of many other commodities like the pce powder would increase in the next few days.
Modern concrete is represented by ready-mixed concrete produced in industrialization, and pumping construction is the mainstream. Mechanical properties are no longer the only technical index of modern concrete, and the control of mixing and rheological properties is particularly important to ensure the construction. At the same time, the requirements to ensure the durability of concrete structures are increasing day by day. In the process of production and use, we should pursue the principle of sustainable development.
Technical characteristics of modern concrete
More complex components
The wide application of mineral admixtures mainly derived from industrial solid wastes diversifies the composition of cementitious materials, which is one of the main characteristics of modern concrete. Conventional mineral admixtures such as ground slag powder and fly ash have become important components of modern concrete, and functional mineral admixtures such as silica fume, ultra-fine stone powder, calcined kaolin and zeolite powder have also been applied in modern concrete. as mineral admixtures, various metallurgical and industrial tailings have been gradually applied to modern concrete. Chemical admixture represented by high-performance superplasticizer is another main feature of modern concrete. the emergence of high-performance superplasticizer greatly reduces the water-binder ratio of concrete, and the strength of concrete has been greatly improved. Ultra-high-strength concrete above C100 has achieved high-rise pumping construction. Some special materials are also gradually applied to modern concrete, such as expansive agent, fiber material, air entraining agent, consistency adjustment material, density adjustment material, durability reinforcement material and so on. In terms of concrete aggregate, high-quality natural aggregate resources are increasingly scarce, machine-made sand and low-grade aggregate have begun to enter the field of ready-mixed concrete, and the water absorption and mud content of aggregate are increasing. With the complexity and diversification of modern concrete components, the initial fluidity of concrete is greatly reduced and it is more difficult to maintain the fluidity of concrete.
Higher construction requirements
The complex structure and harsh construction environment of modern engineering require higher and higher fluidity of concrete. The construction of super high-rise, super-large volume and complex structure requires excellent pumping performance of concrete, and can realize self-compacting construction, so as to reduce labor intensity and ensure the compactness of concrete; long-distance transportation or long-time pouring requires a long time to keep concrete fluidity; nuclear power and hydropower projects require concrete fluidity to be stable and has little fluctuation over time. The super early strength project requires not only high early strength of concrete, but also long construction time; in harsh environment, especially in the high temperature environment above 40 ℃, the hydration rate of cement is intensified, but concrete is still required to be pumped for construction after 3 hours. Therefore, high fluidity and fluidity, good and workability, and can achieve self-compaction is the fundamental to meet the requirements of modern concrete construction.
The problem of shrinkage cracking is more prominent.
The large amount of modern concrete cementitious materials, finer and finer cement, more and more complex components and lower water-binder ratio make the problem of shrinkage cracking more prominent. The simple pursuit of high profit to meet the strength makes the effect of cement through grinding aids become finer and finer, the specific surface area is as high as 420m2/kg, the hydration rate is accelerated, the hydration heat release rate increases, and the internal water consumption rate of concrete is too fast, and the development of high strength reduces the water-binder ratio to 0.18 and free water. The extensive use of ultra-fine mineral admixtures increases the shrinkage of concrete, increases the sensitivity of cracking, and makes concrete more prone to shrinkage cracks, thus reducing the frost resistance, carbonation resistance, corrosion resistance and so on. In addition, with the continuous expansion of the scope of human activities and the progress of construction technology, concrete projects in harsh environments such as dryness, cold and heavy corrosion are increasing day by day, and modern concrete is facing a harsher service environment than traditional concrete. the risk of cracking increases, and the problem of durability is more prominent.
Why is polycarboxylate superplasticizer more suitable for modern concrete?
The traditional lignin sulfonates, naphthalenesulfonic acid condensates and aliphatic superplasticizers have limited dispersion ability and low water reducing rate because of their inherent molecular structure. even if the content is increased, it is difficult to meet the requirements of high fluidity and fluidity of modern concrete under the condition of complex components and low water-binder ratio. Polycarboxylate admixture has flexible molecular structure and strong designability. Through targeted molecular construction, high performance and functionalization can be achieved to meet the different performance requirements of modern concrete, so as to improve the engineering quality.
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The development of the Russia-Ukraine conflict will continue to dominate the commodity prices such as the pce powder in the future. If the conflict eases or cools, Russia and Ukraine go back to negotiate, commodity prices would fall. However, if the situation between Russia and Ukraine deteriorates further, or evolves into a full-scale war, the price of the pce powder is predicted to see further improvement over the coming days.