Improving the performance of blended cement through the use of nano materials: Dr Raju Goyal, INSEE – Siam City Cement

Good morning to all of you. Once again, you have seen me yesterday. Thanks, Thomas, for my repeating of my CV today. Thank you. So Peter, thank you very much for setting up the context for my presentation again today. As you have seen that whenever we talk about the composite cement or blended cement, whenever something SCMs is added, the list of the challenges, what Peter has presented exactly comes when we talk to the customers. So when we discuss about the coming of these low carbon cements, low carbon cements only can be achieved when clinker is reduced in the cement. That's the way it's been seen so far.

For that, we have to use the SCMs or the different materials which can reduce the clinker content in the cement as well as make the performance of the cement equal to that. Unfortunately, whenever we use the SCMs, performance of cement compared to the CEM I or OPC is not as par. So this work what I'm going to show you that this is some work which I did in about the last four or five years. When I talk to the customers, customers always say that I do not know about the CO2, but I need my performance of cement as good as OPC.

So thought was came, what can be done to improve the performance of the SCMs in the cement, in the blended or composite cement to make the product as good as equal to CEM I or OPC or better than that? So what we have done, we have done lot of research was already done. So I worked on these nanomaterials. This can be the futuristic activation of the SCMs or activation of the materials to improve the performance of cement, if not equal to, but better than or at par with the OPC.

So when you call the blended cement, as you have seen the presentations, all the material coming out from the industrial waste, fly ash, s**g, silica fumes, or natural product like a limestone, volcanic ash, as other materials can be used with the clinker and that is giving the hydraulic property of the cement to give the mechanical property as well as the durability and the workability. Same time, these SCMs also reduce the CO2 content of the cement footprint. How to produce the blended cement? Each country have their specific SCMs availability. Some people have the fly ash, some people have the s**g. Take the example of Thailand.

We have the limestone, very limited quantity of fly ash or s**g. Calcined clay is new material is coming up, which we are talking about a lot. Industrial and agricultural waste or agricultural ash is also being seen as a new SCMs, but the availability as well as the scalability is always a problem with the biomass ash. Natural materials are there, or other materials which can be linked, grind with the clinker and gypsum to make the blended cement. But they also require the same performance as OPC, physical, chemical properties with the defined standards, as well as the supply of the material is always a issue to meet the requirement of the SCMs or blended cement to reduce the CO2 footprints.

There's a number of sources for the SCMs, and SCMs can be produced. It has been seen the performance of the cement also change how you make the cement. If you put more than 30% SCMs are added with the clinker and you grind in the co-grinding, the performance of the cement is not as good as grind separately or make premix or that one. So separate grinding and the blending will be one of the best option for the large scale of SCMs when we produce the blended or composite cements. Just to tell you, Peter also mentioned that the SCMs are already in scarcity, number of the markets.

But coming back to the point, we have lot of limestone and the clay compared to the other materials, and how these materials can be used to produce the SCMs to produce low carbon cements. Just this is the simplified graph of the Peter, what he mentioned that as good as up to 70% CO2 can be reduced based on the current standards, based on the prescribed standards, not the performance-based. Performance-based can go to 90% or plus CO2 reduction, but based on the standard, up to 70% of the CO2 footprint can be reduced if we use the proper SCMs. SCMs or the blended cements are not new in the market.

If you see in the past 10 or 12 years, SCMs or blended cement in the market, especially in the Southeast Asia, because the bag market is prevailing here, is not been adopted very significantly, especially in the bag market or the cement mortar applications. So when we discussed that, the reason came out that because these materials are having the negative impact on the cement performance. And these SCMs have the very significant role for decarbonizing of our industry. As we talked yesterday, almost 60% calcination CO2 and 30% fuel and 10% others, which is the electricity and other materials. And if you see in that whole scope one, two, three, scope one is almost 75-plus percentage.

This is the biggest animal for us to manage in our decarbonization. And this 70% CO2 can be managed by number of initiatives, but I will take that one of the biggest one is the clinker factor reduction and the product portfolio. Product portfolio, different type of materials usage in the cement, which is called a blended or composite cement, which will be helping us to reduce our decarbonization journey. This is just a picture again. What I'm trying to say to here, if everything is new green, electricity is green, fuel is green, it's still 60% emission will remain in our product. And if this 60% product we use in the OPC, which is a 5% gypsum, we can only reduce 5% of CO2 in our footprint.

If we use the SCMs, up to 70% CO2 can be reduced by using the various type of materials. In our NC, we have clinker factor up to 67%. It means 37% CO2 we are producing less than other materials. These are the few materials I put in the picture side, which Peter has spoken. And different materials have a different intensity to mix because their characteristics, their properties, or their impact on the hydration process is very different. So these materials can be used in different compositions, depends upon the chemistry, depend upon their mineralogy, can be used from the 5% to up to the 70%. When they added to that, cement performance also reduces or have the impact on that.

If we use the nano materials, these compositions can be further improved or further enhanced to improve the mechanical as well workability and durability of the cement. When we use the blended cement, they have plenty of advantages from the durability point of view. They have crack-resistant properties. If you use a blended or composite cement, crack is very less. They improve the resistance for the aggressive environment like sulfur or chlorine or any other acidic environment. They're much more robust against the normal OPC. They have the lower shrinkage. Reduce the heat of hydration.

If you go to the mass pouring or the very big structures of the concrete, you do not need heat content into the concrete for avoiding the life of the concrete. Alkali level of the cementitious material into the blended cement is very low. So you can have the variety of the aggregates which can minimize the risk of alkali-sulfur reactions. They also improve the strength of the concrete in the later strength, not the early strength, but later strength can be improved. And rheology, if you remember that the point which Peter mentioned that very significantly rheology. Alejandro will talk about that more with these chemicals on that.

Rheology is one of the biggest considerations for the concrete producers as with the mortar applications people. Given all these benefits, they're the significant tangible or noticeable negative effect of blended cement into our applications. They have very longer setting times, initial as well as the final setting time. Their early strengths are very delayed. They have later strength also delayed. Water requirement has increased significantly to using the SCMs. They also need higher doses of grinding aid or admixtures, which is adding the cost. With this all things, if you talk to the construction industries, they say, "Guys, give me the OPC.

I will be happy with that OPC, not the blended cement." Because it increases their duration of the project, because setting time and strength development is slower than OPC. Their project cost goes up. They need more time for the labor to wait for the speed of the project. And definitely, they produce lower economy for the construction industry. So this has been seen as a barrier for using the blended cement in the market. So what we did in this project, we used the nano silica to improve the performance of the material.

So I have used the nanomaterial in different ratios to see that where the sweet point or where the best options for the industry, which I can provide the solution for the construction industry to make SCMs more favorable than OPC. So you can see that here, if I use the 1% of the nano silica in the slag-based cement, your initial setting time can go much lower, almost 30% lower than the pure blended cement. And final setting time also reduced significantly with 1% of nano silica only. What happened to the strength? Because this is the one parameter which everybody monitor. For that, if you see the orange color in the second line, strength drops significantly.

But when you add 1% of nanosilica, strength increases almost 45% to 50% in your one-day strength. And 20-day strength, you can see in the graph with 1% of nanosilica is much better than the OPC. So this material can offset the drawbacks or the negative impact of SCMs in the blended cement and can be comparable to the OPC or cement which is the preferred material for the construction industry. So I did some test with the calorimeter to see that what happens into that. So it is proven that due to the presence of the nanosilica, due to the nucleation process and the early hydration reaction starts, the heat curve shifted.

Means the activation or the hydration processes start much earlier in presence of even the SCMs compared to the OPC. Which is giving the indication that these results, what we have seen before, is much more reliable and much more technically proven that SCMs can be activated in the presence of the silica. Then we also study with the SEM, electron microscopic, we have seen that. You can see that in the presence of the nanosilica, this one here. In the presence of nanosilica here, this bottom line this, a structure is much more dense because the more hydration product has been produced in presence of the nanosilica because they provide the nucleation, it start hydration process in early stage.

Which is improving the overall mechanical performance of the cement. Then we talk about the chemical reactivity or the aggressive environment, how they perform. So we have taken a pure H2SO4 and HCl to say that how they react in harsh environments. Here we have proven that compared to the pure SCM cement or the pure s**g cement, in presence of the nanosilica, their resistance to the harsh environment is improved significantly. This proves that it is a durability point of view, is also enhance your performance of the blended or composite cement. So this study was on that is like a slag-based cement. Similar study was on the fly ash-based cement also, up to 35% fly ash replacement.

With respect to the CO2 reduction, almost 26% reduction, 74% reduction in the s**g, and almost 37% reduction in the PPC, or sorry, pozzolana cement or fly ash-based cement can be achieved by maintaining the similar properties of the blended cement almost equal to the OPC, and same time you can have the better durability, better mechanical and workability of the cement. Of course, there is a few challenges there. So when I published this work, so one of the professor from US has challenged me because cement is a micro material, and now we are adding the nanomaterial, how this mixing can take place in this? Dispersion of the material was one of the biggest challenge all the scientists has seen.

I was also challenged, so I have checked what is my blending efficiency or the dispersion of my nanomaterial in the whole mixture of the blended cement. I found that almost 96% dispersion was achieved in that, which is saying that the dispersion of, or mixing of the macro and nanomaterials has been achieved. To achieve that, I used a system called turbo mixer. Is very high speed turbo mixer with the high capacity. I can mix it much more better and dispersion as well as the spread of the nanomaterial was uniform into the system. So this problem can be also resolved. Then point was on the safety because nanomaterials are very small.

When you use on the site, it can have the health hazard or environmental hazards. For that, we have seen that because now market is growing for the concrete side or the pre-concrete side. So this material can be produced in the factories under the controlled conditions, and this can be sold as a readymade solution, not on the site mixing, which can solve the problem of the health and safety also. Last but not the least point, which Peter also mentioned that if nothing is economical is not much favorable. So economics also has been calculated because it is reducing the significant CO2 footprint of the cement with respect to the same performance.

We can get the performance and CO2 reduction same time. So if your tax or the carbon ETS or the cost $15 to $20 per ton is being added and can be offset by the tax or CO2 tax or CO2 penalty or whatever you call, it can be offset the process of high cost in using the nanomaterials. Same time, I'm also working one of the startup to reduce the cost of nanomaterials, and first trials has been completed. Synthetic silica has been produced, which is much more cheaper than the normal silica which is available on that site. So economics can be worked out if ETS or the cement have the CO2 penalties.

In conclusion, yes, this is the one of the best way to reduce the waste in the environment, use into the productive material, which is the cement, cutting the CO2 footprint. Nanomaterial can offset the drawback of the cement properties, which is brought by the SCMs, different SCMs or different materials, waste material which is used into the Portland cement. And they increase the performance equal to OPC or much better than the OPC. Blended cements are much more stronger in long terms. They're more workable and great for the planet.

Cement industries can act as a waste recycling industry to provide the solution for all the other industries, circular economy, by adding the nanomaterial into their product. Yes, there is a full techno-economical studies need to be done for their applications in the different geography, on different market, subject to the chemical and physical property of their nanomaterials or their SCMs. For me, this last word I say that the nanomaterials can be the futuristic material for driving the low carbon mission for our industry. Thank you very much.