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Additives for competitive limestone cement in Asian markets: Jorg Schrabback, Sika Services AG (Germany)

Filmed at Cemtech Asia 2015, 21-24 June, Grand Hyatt, Bangkok, Thailand

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I want to talk about Limestone cement and especially about competitive Limestone and for that's perspective I want to first define what means competitive. In general it's to offer solution which allows gaining a technical or economical advantage compared to other available solution. This can be on the one side in construction material, for example concrete versus steel as you can see at the picture from Singapore skyline, it's really competitive solution over there. The different skyscrapers using different technologies, everyone tries to be the best, the most efficient. So we've to ask the questions then, what is the cost performance or in other words how much benefits do I get for the cost which I have to invest? But I also have to ask the question, do I have the possibility to achieve the same performance with a different way? Finally, what would be the cost of this alternative solution?

So, what applies to concrete applies also to cement. I have cement from Producer A, and cement from Producer B, or Limestone Cement versus Fly Ash cement and so on. So, I always can compare different solutions, and I always have to ask myself what is the cost performance? Do I have different possibilities to achieve the same performance, and what is the cost for that?

And finally that applies also to chemical additives. I have chemical additives from Producer A or B and I have Technology C or D, so I can compare these technologies, and always these questions of cost performance apply. So, the target is to provide the competitive edge, and in this case I'm talking about the competitive edge which the chemical industry wants to supply to the cement producer.

We heard a lot about the cement market share in Asia and I don't want to go into detail. It's a very important mark, it's dominated by China but we also have very big market here in South East Asia. However, it's still very large proportion of ordinary Portland Cement which we find here in this market, which offers a huge potential to cost savings and environmental benefits using blended cements. However, there are strong differences within the region and that applies on the one side to the industry and available clinker replacements, but naturally also to the local challengers and to the local standards which are necessary to follow.

So, Limestone is a key element to improve the plant profitability, to reduce the carbon footprint, and to achieve cement volumes which are necessary to fulfill the market demands. The share of Limestone varies quite significantly in the region from zero or 5% in India and Thailand to quite substantial parts in the Philippines, and Indonesia.

And also the composition varies significantly. When we see, we sometimes have only 10% Limestone in the cements while other producers go up to 30 or even more percent. Limestone offers a lot of opportunities, it's the material which is the most available, so we have even more Limestone than clinker naturally.

So the lowest footprint, carbon footprint, and the lowest cost. So, Limestone is a very attractive clinker replacement which should be considered. However, it incorporates technical challenges. One of the challenges from the production point of view, yes it's true, Limestone is easy to grind and with this we can easily achieve the Blaine value but we also have the big risk of coating of the mill internals which then negatively affects the production.

Frequently, people struggle already just to incorporate 15% of Limestone because the material is easy to over-grind and then has negative effects also on the clinker grinding. And finally, also the workability of the concrete which is produced afterwards is affected by Limestone because this high fineness affects the water demand which triggers the loss of concrete workability and elevated admixture consumption.

So, how can we ensure that we achieve the quality? We know from ordinary Portland cement that we need to shift the particle size distribution into this range of three to 30 microns, if we want to improve the strength and we want to avoid over-grinding particles. So particles which are, let's say smaller than half a micro meter, but with Limestone we have a special challenge because it is easy to grind and it leads to a high amount of very fine particles.

Which means the tendency to agglomerate is improved, or enhanced or strengthened by Limestone. These fine particles don't contribute to strength. They are only blocking the grinding of the clinker particles and we made some deeper research on that and ground Limestone to different finenesses and it became very obvious that besides the negative effect on workability, we have no positive effect of an increased Limestone fineness. So, the target has to be to avoid Limestone overgrinding in order to gain clinker grinding because clinker is the material that leads to the strength.

So what happens with the Limestone particles in the mill? When they are ground they have a high surface energy, so they agglomerate and you can even see that in the cement when you have this small agglomerations which are even visible with our own eye. While when you're using a grinding aid, you have a reduced surface energy which allows the particles to be dispersed and with this, the material is free flowing which makes it easy to separate these particles, the course particles from the fine particles and it minimizes the coating of the mill internals and with these increases the mill and separator efficiency, which means high production rate, low energy consumption, which is good.

On the other side, this better particle dispersion leads also to good powder flowability which is then important to achieve a low pack-set value and easy handling. So, but how to achieve that besides just using cement additives, it's the thing, the Limestone particles when they are dispersed they flow easily through the mill and leave the mill as soon as they are sufficiently fine. This leaves space for the clinker to be ground, because these clinker particles are harder, it takes more time them to be refined and then they stay longer in the mill and they have the space.

So, with this we improve the production as well as the quality of the Limestone Cement. And that's the first step of a threefold approach in order to gain quality, the production with the focus on getting Limestone as fast as possible through the mill. The second part is using cement additives which I already mentioned with a strong particle dispersion, but we can also add cement additives with strength activation, which enhance the strength development, because this is necessary to compensate the loss of strength which comes from higher Limestone amounts.

And for sure, we can also supply products which enhance the workability in general, and the most important thing and that's why I put it at the last on this slide is to extend the finest analyse. Frequently, I recognized that people are stuck on the blend value. Blaine value is very easy to measure and it's very common worldwide, but it gives only a very, narrow view on the quality of the cement and what I recognized is, especially for Limestone Cement, sieve residue is much more important or the particle has distribution. So, if we want to produce a good blended cement and especially good Limestone cement, we need to incorporate these additional finest measurements and not just on the basis, three times per day, but really on a regular basis. I've seen it very often that the Blaine value was lower and the people said, it's difficult, the quality will not be there but the sieve residue was okay and we had finally an excellent strength. So, especially for the strength, sieve residue is of highest importance. I want to show you a case study from Vietnam in which the reference situation was that they used 8% of Limestone, Blaine value 4100 and sieve residue 4.7%. So, in the first step we applied strength enhansion just to see what is the effect of the strength enhancing solution.

Loss a product from the SikaGrind range we had it on 450 grams per ton. As you can see the Blaine value and the sieve residue remain the same. In the second step, we then reduced the clinker factor by 4%, so we've and finally 12% Limestone still at the same Blaine and sieve residue. Now is the interesting point, what happened with the strength. In the first step, we can see the strength has increased by approximately four megapascal in general which allowed to reduce the clinker by 4% and still have a higher final strength. So, that's a very logical result which comes out.

The strength enhancement is achieved by the chemical component and then when we reduce the clinker, we compensate this strength increase with a loss of strength because of the higher amount of Limestone, but as you can see we're overshooting the final strength, so we won't have opportunities to improve the situation.

We could on the one side, increase the clinker further on, but as you surely notice that would lead to a lower early strength. So we could accept lower early strength if this is accepted by the market and with this optimize the cost, but we also could say, okay, to have a higher clinker replacement is more important so we add to the chemical additive a further strength enhancement for early strength in order to compensate that. The third option would also be to say we're satisfied with the 4% increase of Limestone, so we optimize the chemical additive to make it a little bit cheaper. What is more cost efficient is the other question, that's why I am looking at it and say okay.

Taking that clinker costs approximately USD 30 per ton, Limestone approximately five, the 4% clinker replacement will lead to a saving of USD 1 per ton. Deducted by the treatment cost, you would still have a net saving of 20 cents per ton of cement and for three million tons per year planned, this means you have USD 0.6 million less material cost, but you also have profit from 150000 tons more cement that you can sell or export.

Whatever you prefer for your local situation, and in total that would mean you have then $2 million saving plus approximately 100000 tons less carbon dioxide emission. I was very glad to hear yesterday morning that green products are also coming more and more into the Asian markets, so from the production perspective, we see that the grinding rate has a positive effect on the production rate and obviously when I add a product which is easier to grind, I also increase further the production which was then up to 16%.

If I calculate here the economical benefit I come to a range of approximately $1.1 million per year which means that in total the reduced raw material cost and the energy cost savings adds to a profit of more than $3 million per year. Naturally, we've been also have to ask a question can we further improve that, because 12% Limestone that's not really the big challenge and usually people then want to make laboratory tests and there you typically run into the situation that the water demand and the strength results are not in the range that you would like to have.

Why? Because we compare the system in which we take out the fine particles constantly in the real production with the system in a laboratory where we have a batch process and where all the particles are stuck so they can not escape, so you get lot of overground particles, but bringing particles which need to be refined are usually insufficiently wrong.

So it's better to have a different approach which we follow in Sika, we grind separately the ordinary Portland cement and the Limestone and then we blend it and determine the strength development. That's done without a grinding aid in order to really see just the fact of the dilution of the Limestone, and with this you can easily evaluate the approximate potential amount of Limestone that you can add, because you know where you want to reach and you can then say okay, I analyze, 10, 20, 30% Limestone.

I choose something like 25 because it's somewhere in between this range, and it determines the need for strength enhancement which you need from the chemical component and then you make analyzers with this blank cement and you just add the strength enhancer and you can make that with an OPC or with a blended Limestone then, but blended Limestone mixed after separate grinding. And then you see, you have solutions which enhance the final strength, you have solutions which enhance only the early strength and you have solutions which enhance both early and final strength, and very logical when I have more Limestone in the mix.

The general strength enhancement is smaller than if I have a small amount of Limestone. This allows you to select the product which achieves the set target in the best way, and with this you go then to a plant trial and analyze and always keep in mind, get the fine material, the Limestone as fast as possible through the mill.

And this brings me to the second case, also from Vietnam, there we had a much higher Limestone content of 22% in the reference situation, there we went then directly to the clinker reduction because the experience from before allows that. We used only 350 grams of secret grind products and if you look at the strength despite 4% less clinker, we still gained significant increase of strength. So, this offers again the opportunity to further reduce the clinker or to reduce the dosage when we want to determine how much we can reduce the clinker further, we can use the rules of thumb and we know that approximately that one megapascal equals to 2% clinker replacement, so from the early strength perspective we could reduce four megapascal, 4% from the late strength, we could even reduce 7% of Limestone.

So when we just look at the total of 8%, four plus four then and compare the economical effect we see that with this 4% Limestone replacement we have a net saving of $20 cents and this leaves for two mega tons, million ton plant to a profit of $0.4 million per year. If we look for the 8% replacement this leads to net saving of $1.2, so significantly more because the treatment cost is not changed, the treatment cost is still the same, but I have the double replacement.

And an annual profit of US$2.4 million and if I calculate that with the additional cement which I can sell or export that accumulates to almost $5 million per year. So, you see it brings much more benefit to say okay, how can I reduce the material cost as much as possible? It should not be that hard to say what's the lowest cost for the cement additive that I get, I win a couple of dollar, but I win millions of dollar if I optimize my cement composition.

Naturally I don't need to focus on that, we've seen that in the first case already, if I have finer material and easier to grind material, production rate increases, especially when I use good grinding aid. But there is an additional advantage which is not covered at all at the moment, and that's the workability of the concrete which is produced afterwards.

And the target should be in this example which is actually from Europe to maximize the Limestone content and on the other side maintain the strength, and the target was this 18% Limestone content, were the benchmark, and they want to avoid that the workability gets lost and what you see there, the blue line and the black line.

The blue line is the 18% Limestone content and the black line is the 29% Limestone content. So you see the workability significantly suffers when I increase the Limestone content, but using a special design product allowed to achieve the strength, the workability and maximize the Limestone content to 34%.

So, right at the limit of the European standards. And if we make an economical evaluation it becomes clear that saving of raw material cost is already US $4 per ton and even if the treatment cost would be very higher because there's a very special product that a high dosage even if it's $2.9 treatment cost, which is a real big value.

I still have $1.1 million saving for this small one million ton plant. So I think if you transfer that to the Asian market where we usually have larger plants we could really make some good benefits for the cement industry in this market. Naturally, Sika has published over the last years a lot of specialized articles which have all these key informations inside.

We've special articles about production rate, about strength development, Fly Ash cement or Limestone cement and all of these articles include very valuable case studies from the cement industry which were made directly in the industry, and I would like to invite you to come to our booth and discuss with us about all these details and that brings me to the summary.

Chemical additives facilitate the production of Limestone Cement, they enhance the strength and enable clinker reduction and they compensate water demand. Besides that the plant profit is significantly larger than the cost for the chemical additives which means it's a competitive solution. Sika supports you with adjustment of the mill operation to a higher Limestone contents and offers you special articles which describe the international findings and case studies.

That means that chemical additives enable supplying competitive Limestone cements also on the Asian market. Thank you very much.

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