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

The World Platinum Investment Association (WPIC) said recently that carmakers are accelerating reductions in palladium use and increased use of platinum due to concerns about Russian palladium supplies. However, it still expects a significant surplus in the platinum market this year.

Palladium is used by carmakers in tailpipe emissions systems to reduce carbon emissions.  While carmakers prefer palladium for catalytic converters, they are turning to platinum, which is cheaper than palladium, to save costs.

Russia accounts for about 25-30% of the world's palladium supply and 8-10% of its platinum supply.

There is no sign that western sanctions against Russia have restricted palladium exports since the conflict escalated in February, but as the conflict continues, more companies could boycott The Russian metal and governments could impose restrictions.

Platinum is currently trading at about $950 an ounce, about half the price of palladium.  Automakers use about 2.5 million to 3 million ounces of platinum and about 8.5 million ounces of palladium each year.

For the year as a whole, platinum supply will be 5 percent lower than in 2021 and demand 2 percent higher, with the automotive sector seeing a 16 percent increase due to increased light vehicle 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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In a recent interview with Izvestia, Russian Federation Council Chairman Matviyenko said that Russia is open to dialogue with the West based on mutual respect, but the opportunity to resume dialogue will only come after the end of special military operations.  

Matviyenko also noted that Europe currently lacks politicians who can make independent decisions.  She said the EU's strategy to wean itself off Russian energy by 2027 would be costly, with Russia supplying 40 percent of Europe's gas, 27 percent of its oil, and 46 percent of its coal, and was essentially "anti-European" and a "tax" on US global dominance.

On Sweden's and Finland's plans to join NATO, Matviyenko said Russia will take corresponding measures if NATO weapons and equipment appear in the two countries, and Russia is capable of guaranteeing its own security. 

Besides, speaking by video at an international conference, Ukraine's minister of agricultural policy and Food, said the country's grain pce powder are expected to continue to be influenced by international situations.

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