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Effect of Limestone Powder in Machine-made Sand on PCE powder

Yesterday, Nancy Pelosi, speaker of the US House of Representatives, arrived in Taiwan, becoming the highest-ranking US official to visit Taiwan in 25 years.

The move was interpreted as a direct threat by China, which claims the island is part of its territory, and Beijing has repeatedly warned the US that its military will not "sit idly by" and "will take strong countermeasures".

As the international community waits to see how China will react, chipmakers in the business community are already feeling the pain of the brewing conflict between the US and China over Taiwan.

Semiconductor stocks tumbled on Tuesday in anticipation of Pelosi's visit to Taiwan.

Shares in TSMC, the world's largest and most valuable semiconductor maker, worth $440 billion, fell 2.4 per cent on Tuesday. Its Taiwanese counterparts United Microelectronics and MediaTek fell 3% and 1.6% respectively. Meanwhile, shares of the US chipmaker Intel fell 1.5 per cent on the same day.

As Ms Pelosi prepares to meet Taiwan's president, Tsai Ing-wen, on Wednesday, technology investors are keeping a close eye on her actions-and any signs of retaliation from China. In the event of a dispute between China and the US, chipmakers, especially in Taiwan, are likely to be collateral damage.

Because of the turbulent international situation, the supply and prices of many international bulk pce powder are still very uncertain.

Natural river sand has been exhausted after decades of large-scale mining, concrete production enterprises began to use machine-made sand as fine aggregate on a large scale. Some limestone powder will inevitably be produced in the process of machine-made sand preparation, which will not only affect the performance of concrete, but also affect the effect of polycarboxylic acid admixture.

The results show that stone powder has different effects on the working properties, mechanical properties, chloride penetration resistance, sulfate resistance and freeze-thaw resistance of concrete. Stone powder can play a physical filling effect in the cementitious material system, which can reduce the water secretion of cement paste, improve the dispersion ability of cement paste, and can also be used as the crystal nucleus of calcium hydroxide to accelerate the hydration of cement particles and affect the pore structure of hydration products. Stone powder can adsorb polycarboxylic acid superplasticizer molecules on the surface, which can reduce the saturation point of superplasticizer under certain conditions, increase the initial fluidity of cement mortar, reduce the time loss of fluidity of cement mortar, and improve the compatibility between superplasticizer and cement.

 

Effect mechanism of limestone powder on water-reducing effect of pce powder

The hydrophilicity of limestone powder particles is low, that is, the adhesion of water molecules on the surface of limestone particles is small, which makes limestone powder have a certain physical water-reducing effect. In addition, limestone powder has a larger specific surface area than cement and has the filling effect of micro-aggregate, that is, small limestone particles can fill the pores between cement particles and replace the free water between cement particles. This is the aspect that limestone powder is beneficial to the water-reducing effect of polycarboxylic acid.

 

At the same time, polycarboxylic acid superplasticizer can be adsorbed on the surface of cement particles and on the surface of limestone powder, that is, there is competitive adsorption of polycarboxylic acid molecules between limestone powder and cement in the paste. this will reduce the density of polycarboxylic acid adsorbed on the surface of cement particles, and then reduce the water-reducing effect of polycarboxylic acid. In addition, the limestone powder with larger specific surface area needs more water, which will reduce the fluidity of the slurry. This is the aspect that limestone powder is not conducive to polycarboxylic acid to play a water-reducing effect.

 

The above analysis shows that limestone powder has both positive and negative effects on the water-reducing effect of polycarboxylic acid. In the case of low content of limestone powder, because the hydrophilicity of limestone powder is low, and the filling effect of fine particles is easy to play, the favorable effect of limestone powder on the water-reducing effect of polycarboxylic acid can effectively counteract the adverse effect, which shows that the effect of low content of limestone powder on the water-reducing effect of polycarboxylic acid is not obvious. In the case of high content of limestone powder, because limestone powder has larger specific surface area and higher water demand, and limestone powder and cement have competitive adsorption to polycarboxylic acid molecules, limestone will obviously reduce the water-reducing effect of polycarboxylic acid.

 

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New Delhi: India is seeking to increase its purchases of crude oil from Brazil, the country's oil minister said recently after meeting his Brazilian counterpart.  

India is the world's third-largest importer and consumer of crude oil. Brazil currently supplies only a fraction of India's crude oil imports.  

India's state-owned companies Bharat Petroleum Corp and Oil and Natural Gas Corp have invested in oil and gas exploration in Brazil.  

India, which imports about 84% of its crude oil needs, is reducing its import bill by increasing biofuel use, among other things.  

India's state-owned fuel retailers are increasing ethanol storage capacity by 51 percent and the country plans to double the biofuel blend in petrol to 20 percent by 2025.  

India and Brazil are currently cooperating on biofuels and ethanol.

The prices of many commodities like the pce powder are expected to increase in the future.

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