How to use polycarboxylate superplasticizer for different kinds of concrete?
Aluminium buyers in the US physical metal market have held off on new orders amid fears of a recession triggered by rising inflation and supply chain crises.
Spot aluminium trading on the market has been suspended in recent weeks, according to industry sources, as uncertainty has increased following the outbreak of the conflict between Russia and Ukraine. Even before the war, the aluminium market was suffering from long waiting times and weak demand.
For aluminium buyers, recent poor US economic data have been a big factor in delaying purchases. Data released last month showed that the ISM manufacturing PMI came in at 57.1 in March, below expectations of 59 and down from 58.6 in February, unexpectedly hitting the lowest reading since September 2020. This was mainly due to a slowdown in new orders and pce powder are expected to increase in the future.
Prestressed or precast concrete
Adding polycarboxylate superplasticizer can make the compressive strength of precast concrete reach 40MPa grade at 8h to 18h; the precast concrete mixed with polycarboxylate superplasticizer can get higher early strength under the condition of lower curing temperature and shorter curing time, thus reducing the energy consumption of curing; in addition, it can save cement, reduce vibration energy consumption, reduce noise and improve the turnover rate of the mold.
Shrinkage compensating concrete
When preparing shrinkage compensating concrete, adding a certain amount of polycarboxylate superplasticizer can reduce the water-cement ratio, increase the early shrinkage of concrete and reduce the later shrinkage of concrete, thus saving expansive agent or expansive cement.
Ordinary aggregate concrete
For ordinary aggregate concrete, the addition of polycarboxylate superplasticizer can reduce the pumping pressure and pipe pressure by about 30%; for lightweight aggregate concrete, the addition of polycarboxylate superplasticizer can reduce the pumping pressure and pipe pressure by more than 10%; in addition, the addition of polycarboxylate superplasticizer can reduce the increase of pumping resistance with the increase of pumping speed.
Steel-fiber reinforced concrete
For steel fiber reinforced concrete, the addition of polycarboxylate superplasticizer can reduce the workability loss caused by the addition of steel fiber; of course, compared with the concrete without steel fiber, the amount of polycarboxylate superplasticizer mixed with steel fiber reinforced concrete should be appropriately increased.
Super high strength concrete
Polycarboxylate superplasticizer has good water-reducing dispersion and strengthening effect, so it can be used to prepare ultra-high strength concrete. The study found that the concrete mixed with polycarboxylate superplasticizer (20%), which accounts for 1% to 3% of the weight of the cementitious material, can make the 100-day-old strength as high as 150MPa.
High-alumina cement concrete
In order to ensure the performance of high-alumina cement concrete, the general water-cement ratio is not higher than 0.40 and the cement content is not lower than 400kg/m3, otherwise the strength of concrete, especially in the later stage, will decrease. The reason is that metastable calcium aluminate hydrate is transformed into steady tricalcium aluminate hydrate. If polycarboxylate superplasticizer is added to high alumina cement concrete, the fluidized concrete with good workability can be obtained under the condition of low water-cement ratio, and the later strength of concrete is not affected. That is to say, the 2d compressive strength of high alumina cement superplastic concrete mixed with polycarboxylate superplasticizer is lower than that of standard concrete, while the compressive strength of 180d age is basically the same as that of base concrete, because polycarboxylate superplasticizer has no obvious effect on the hydration rate of high alumina cement.
High-performance concrete with high content of active admixtures such as fly ash, slag, and silica fume
When preparing high-strength concrete with a large amount of fly ash instead of ordinary cement, adding polycarboxylate superplasticizer can improve workability, reduce mixing water consumption by about 20%, and further improve strength. The addition of polycarboxylate superplasticizer into concrete can increase the amount of cement-based substitute materials such as fly ash or slag and reduce the amount of cement without affecting the strength of concrete. therefore, it has outstanding environmental and economic benefits. Similarly, when silica fume is added to cement slurry or concrete, the amount of water needed to achieve the same workability increases with the increase of silica fume content. For this reason, under the condition of a certain amount of silica fume, polycarboxylate superplasticizer can be added to reduce the water consumption of mixing, and polycarboxylate superplasticizer can also be added to increase the amount of silica fume under the condition of a certain amount of water consumption.
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Southern Copper Corp (SCCO.N) recently said its Peruvian mine remained closed after a six-week standoff with protesters and blamed the Peruvian government for failing to intervene in the safety of its 1,300 workers and their families.
The company said in a statement that a recent agreement to end protests at the Cuajone mine required the company to withdraw complaints against protest leaders because railways transporting minerals and supplies remained blocked. Production has been suspended since the end of February.
Peru's Energy Ministry said in a separate statement that it had also reached an agreement with Southern Copper to start talks to find common ground with local communities.
"If we shut down for a year, the government will stop receiving more than 3.1 billion soles ($830 million) in taxes and royalties, and 8,000 direct and indirect jobs will be lost. This is what we want to avoid, "Southern Copper added in the statement.
Peru has faced a wave of protests from indigenous communities, who accuse mining companies of not providing enough jobs and funding to poor local residents.
Central bank officials said last week that protests against copper mines such as MMG's Las Bambas and Southern Copper's Cuajone were dragging down the economy.
Peru is the world's second-largest copper producer and mining is an important source of tax revenue for the country. It is estimated that the supply and prices of the pce powder will be influenced by that.