 Another type of characterization which is normally conducted is morphological characterization. Morphology is basically the shape of the particles, size of particles and so on. Now, this type of study was done by my PhD scholar Dr. Prasad Bhattake, very extensive study he has done and I would like to show you the outcome of the study and you should understand that what type of intricate studies are being done by people in geotechnical engineering. Now, can you identify what this system is? Here I have written confocal micrographs two dimensional. So, this imaging technique is known as confocal micrography which always gives you two dimensional photograph of a grain. So, these are the grains which you normally consider them as standard sand and you say the particles are almost perfect spheres. So, truly speaking the standard sands are of this size and this shape clear and if you look at them at three dimensional which is known as optical micrographs you get the real picture of the sand. So, this is how irregular shaped grain particles are particles of a sands are which normally we use in our studies when we say we are using standard sands and we assume their size and shape to be perfect spheres. So, here I have shown you the micrographs of sands standard sands then senospheres. So, remember senospheres are nothing, but the hollow spheres which are present in the fly ash and these are the glass beads perfect glass spheres of different sizes different diameters. So, when we are doing micro analysis of these systems in terms of morphological characterization what we want is we want few numbers. So, that we can classify the granular material unfortunately granular material is not got much due you know from the researchers everybody talks about defined grain soils much more because fine grain soils are supposed to be much more reactive. So, except for crushing strength you will not find much fundamental work going on in case of granular soils, but here we define a granular material by using its three components that is ferricity, roundness and irregularity. Now, this is the grain which is highly irregular all right and then this was the model which was proposed by Dr. Bartakay if you draw two circles one which is subscribing this and the another one which is inscribing it. So, the radius of the circle which is inscribing is r max in and the circle which is outside is r min circle all right the ratio of this to this will be this ferricity. So, if these two radii are same ferricity is 1 for a flaky particle what will happen r max in will be 0. So, a ferricity number will be 0. So, this is how you can do morphological examination of clay particles then comes roundness you take a particle of the sand the way it has been shown here and try to fit in as many as circles possible inside clear like this is one circle another circle another circle another circle and so on. So, depending upon how many circles you can fit in the inside this area you count them find out their radius divide by number of particles which you have taken and then the radius of maximum radius which is inscribing the material. So, this number is roundness number and regularity is nothing, but the average of the two. So, this is the way you can characterize the granular materials this was interesting scheme which we use for defining the its ferricity of different soils. So, these are standard sands which will be the courses possible sand and the finest sand this is the courses material this is the finest material. So, this is how we define the index associated with this materials all right. So, what essentially it requires is that you have to study at least five six hundred grains of the sand and come up with some average values of s and r. So, the table which you are seeing here is based on the results of about 700 grains of the sands each sand this was the part of his PhD thesis. Yes, the use of this is that we want to understand how interlocking will take place how crushing will take place how shear strength will get mobilized in the coarse grain materials and so on. If you go by the interlocking theory if you concentrate on this figure for some time if another particle is sitting let us say close to this all right and there is a protrusion like this. If you apply external force what is going to happen this particle may get chopped from this plane and that would be one of the ways of defining the crushing strength. So, crushing also has different manifestations associated with it it is only the breaking of one teeth of the grain and it may give you a picture which is not correct. So, these type of studies are required to understand at granular level what is happening in the material what comes to your mind why this type of study should be done and you thought which comes to your mind any other questions related to this or maybe answer or idea what can be done further with this. Suppose, if I give you this map what else you can do see this is the genesis of a very big research idea. Most of the time you talk about void ratios you know e max e min which are very gross in nature where you assume lot of things cubic arrangement, rhombic arrangement of the coarse grain materials based on perfected sphere. But what we are trying to show here is that those models are not correct because we have not looked into the microstructure of the grain and the bottom line is that we are supposed to do something new so for the heck of doing it we have to do all this unless you propose new ideas your papers and your ideas will not sell. So, if we have to survive in our profession we have to think of new things and we have to keep on publishing it has to be some new concept. So, this is what is known as reading between the lines. So, let us talk about physical characterization which most of you have been doing quite extensively. For particle size analysis you normally do sieves or hydrometer tests. Well, this is a sophisticated instrument which is known as image analysis system or particle analyzers also sometimes call it laser particle analyzer also sometimes you call it. So, there is a microscope kept here tabletop you can spread your sample on this pedestal and you can please the picture. There is a PC connected to this on which you can see on the screen you can see different types of shapes or the particle and basically it is a statistical analysis. I will show the results of this sometimes you can use ultra sieves you might have seen in the lab where you can do dry sieving to get the particle sizes and what you end up is with a particle size distribution cracks. So, in my opinion whenever you do a direct shear test on sands you should always work out its particle size distribution before shearing and after shearing and you should see the difference why it is required. The difference should be studied to ascertain that no significant change has taken place in the material which has been sheared clear. So, these are all parameters which are normally considered when you are talking about the mechanical response of sands. Well, these are the results of laser particle scanning system or the soft imaging system which I had shown you earlier. You have to literally count the number of particles which are present in a batch and the particle size. So, what this analyzer does is for different particle sizes it gives you a range. So, let us say from 2 to 3 micron the number of particles is approximately 900. So, literally you have to count 1 by 100 particles 1000 particles and so on research is not so easy and each test you have to repeat at least 5, 6 times. So, that you may get the representative value this was done by Dr. Krishnaya who was that J N T you now is now this is from his P I D C S. You will notice here that if you do the analysis for silica fume first of all the question comes that why should we do this analysis for silica fumes can not you find out particle size distribution by some other method. No, why? First of all they are all submicronic particles and they are much lighter than air. So, even you make a slurry of it nothing will settle down. So, hydrometer cannot be done. Why sieving cannot be done? Yes, there will be lot of losses and nothing will pass through the sieves. So, in this case situation soft imaging analysis becomes the best option where you can magnify the grains and you can see their shape and you can count what is the size. This is the table which gives you different properties of the materials. So, fly ash as you can have specific gravity of 2.0, 2.3, 2.1 for silica fume a specific surface area if you look at it is almost 2 lakh centimeter square per gram. That means, 20 meter square per gram is the specific surface area of this material. So, the question is how to find out the specific surface area of this type of a system. I will show you how specific surface areas are determined. And this is the analysis for different materials fly ashes and glass furnace slag silica fume. What you will notice is in the range of 0 to 3 microns you have approximately 4,000 particles. So, your hydrometer analysis cannot be done for particles less than 2 microns. So, 0 to 3 micron range basically corresponds to 0.003 micron range, but then those who are working in concrete and HVFC they are they require this type of classification of the material. So, you will find that in the range of 36, 39 microns nothing is available for this material and that is the reasons why fly ashes and silica fume and ggbfs they are used in concrete. So, if you remember the basic idea of using this material says that you can seal the pores and you can make a concrete which is much more durable. This is partly any doubts. So, from the number of particles then you can compute the percentage of particles and then you can plot it in a form of a histogram the way it was done earlier. The second attribute of the materials is specific surface area. Why specific surface area is so important to be determined? It shows the reactivity potential. All right. How much reactive a material would be? So, more finer a material more surface area highly reactive with the water environment contaminant and so on. So, that is why most of the studies in presented geomechanics deal with precise determination of specific surface area. Now, what is the difference between surface area and specific surface area? Why do you call it specific? Correct. So, specific surface area is always surface area divided by grams per unit gram of the material. So, that means 1 gram of the material of silica fume gives you specific surface area of 20 meter square. What is the size of a hockey field? Any guess? You are interested in any sports? What is the size of a swimming pool? Sneha. The new one is 50 by 25. The old one? No. It is 28 by 23, 22 approximately meters. All right. So, this comes out to be approximately how much? 400 meter square. Clear? So, one tenth of that will be approximately 40 meter square. So, that is the surface area of each particle of silica fume. Just imagine. So, when you go for assembly of the particle, the reactivity is going to be so high. It is just to give you an idea about what surface area is all about. So, this is why mineralogy which has been ignored till now by geotechnical people is becoming more and more. It is coming in more and more limelight and everybody wants to study at the micro level and this is where all these characterization schemes and tools become very important. I hope now this point is clear. So, when we talk about specific surface area, there are different techniques. These instruments are very expensive. All institutes and organizations may not have them. That is why Government of India had set up advanced center for research in different corners of the country. There were five you know CSREs type in the entire country. These are known as regional sophisticated instrumentation centers. One of them is located IIT Bombay which is known as SAIF now. So, the first instrument which is normally used is BET nitrogen adsorption. This is now available in chemical engineering, metallurgy and chemistry department. To my knowledge, the recent version of this instrument costs about 50 to 60 lakhs. Then second instrument not sorry it is not instrument is a method absorption of ethylene glycol monosylene ether. This work was done by Dr. Nidu. He is an expert in determining surface areas of the soil. Another student professor at IIT Chennai. So, he spent enough time in coming up with a methodology and showing that which method out of all these is the best method for determining specific surface area of soil. Then there is a method known as methylene blue, MB dye method. It is a dye which you have to put in the soil mass depending upon the absorbing capacity of the soil. The concentration of dye gets reduced and then you can use a photospectrometer to determine how much concentration of dye has been absorbed by the soil mass. Detect the two, find out the percentage and that is what is related to the surface area. Mercury intrusion porosimetry which we have shown you the other day when you came to the lab. MIP is also used for finding out the surface area of the grain, but not a very good technique I would say. Helium gas spectrometer can also be used for determining the surface area and blend separators. You must have I am sure that you might have used this blend separators in the undergraduate for determining surface area of cement or sand. It is also known as air permittivity method, blend permeability. So, this is the MIP, mercury intrusion porosimetry. You have already seen that helium gas spectrometer you have seen. Now, this is the blends permeability apparatus for finding out the specific area. Now, this is as per ASTM C204 for admixtures and photonomic materials and issue is that you use here as a reference material the Portland cement and for Portland cement the specific surface area is 3460 centimeter square per gram. So, what do you think that this method can be applied to any material or there is some constraints limitations yes not below not not below higher. So, the materials which are finer than cement particularly silica fume where the surface area is of the order of 20 40 meter square per gram. Most of the synthetic materials zeolites raisins in chemical applications whatever they are using you cannot use this technique. So, if you use air permittivity method you will end up in getting wrong results. So, as per this method the specific surface area can be obtained by using this equation where SS is the surface area of cement which is standard 3460 meter square per gram centimeter square per gram. E is the void ratio there is a tube and above the tube there is a collar in which you keep the sample. So, it is a sort of a manometric tube where you can firm the air in and you can release this air so that the air passes through the sample. So, how easily air passes through the sample this is what you are trying to judge over here. So, E is the void ratio of the sample in this tube E s is the void ratio of the cement these tests are always done in duplicate one with the material for which you are trying to find out the surface area and second test would be done on cement. So, with respect to cement you can always work out the surface area and T corresponds to the time taken by the manometric drop for the standard material that is the cement and T is the time drop for the sample. So, using this equation you can work out the specific surface area not void ratio E s this is a typical example. So, the container which is shown here when you pack the cement in this container it will give you a typical value of 0.5 of E s normally it is a old method. Now, I should say that people do not use this method and they normally go for the method which I have shown you earlier. Just to give you an idea that where the research is in you know cement and cement manufacturing people are trying to maximize the surface area of the cement. So, if you can create a cement of the order of let us say 50 meter square per gram that would be wonderful. Well, this instrument shows you a TGA analysis thermo gravimetric analysis why do you think that these double studies are required you have been finding out gravimetric moisture content all the time is it not by keeping the wet soil in oven and after it dries up you take it out and find out the difference in the weight and then you can work out the moisture content. Thermo gravimetric analysis is normally done to see the stability of the material when it is heated up. So, you should not use a material which is thermally instable particularly let us say when you are talking about admixtures or the materials for their application in concrete at elevated temperatures always what will happen they will simply disintegrate and if they disintegrate the structures are going to collapse. Now, this is a typical result which I am showing you for a TGA and DTA analysis TGA corresponds to thermo gravimetric analysis and DTA corresponds to differential thermal analysis. These are two methods of finding out the thermal stability of the system. So, in thermo gravimetric analysis what you do is you heat the sample what at different temperatures clear. So, with respect to temperature you find out what is the weight loss on y axis there is a weight loss percentage weight loss. So, depending upon the material what is happening here as the temperature increases the weight loss increases this is always from 0 to 100 weight loss. So, as temperature increases the weight loss increases and then it becomes constant alright. However, a DTA shows you there is a hum. Now, what this hum corresponds to this hum basically corresponds to exothermic or endothermic reaction. So, if this hum is above the line of starting point it is always a exothermic reaction. That means, when system is being heat enough it shows heat emitting out of it vice versa if this dips down it takes heat from the system. So, for designing different type of concrete what type of cement should be used in what type of environment in every environment you cannot use the same of cement these type of studies become quite useful and these type of studies are normally done in two atmospheres. So, the first gravity I have shown you is normally in dry air. The same experiment is replicated in inert atmosphere like nitrogen gas. So, what is the difference between the two? In what way you can use these two information? If there are some organic which are present they will not show up in inert atmosphere. So, the difference if you want to make out what is the organic content what is the hydrocarbon content associated with the geomaterial. You can do this simple test and you can work out what is the amount of organic content which are present what is the amount of volatile which are present in the material. So, again this is a very good scheme to differentiate the amount of contamination which is present in the geomaterial. Now, if I ask you a question can you differentiate between this response and this response and what is your intuitive feeling? What it essentially means is that is inert atmosphere the exothermic reaction is less as compared to correct. So, this happens to be a very active material which reacts with the air or the atmosphere and under inert atmosphere condition also it has a tendency to show you some exothermic reaction. So, you have to deal with this material very carefully it is a typical example of one of the fly ashes which we have been working with. So, the whole idea of showing you all this is that lot of intricacies are involved in you know studying the material behavior. This is oh this is basically the difference between the activated ash and the natural ash or the non activated ash. I do not want to go in all those details I just wanted to show you what is the application of this type of study any suggestions or notes proceed further. This is a good relationship with I wanted to show you which is a response in a DSC. DSC also stands for Doctor of Science highest degree in engineering or technology or any subject much higher than the PhD, but here DSC corresponds to any guess essential scanning calorimetry. So, what happens here is you heat the sample slowly and then try to see whether the heat flux is in the sample or out of the sample again the same thing either exothermic or endothermic. Now, whenever there is a drop certain drop what is the meaning of this? This shows thermal instability clear that means material is becoming unstable at this point what it indicates to if you are using this material for fire resistance application it is a misfit. So, as I told you after you know this twin tower collapse civil engineering lot of people are concentrating on now thermal fluxes thermal heating procedures and so on and designing the structures. So, this is where the steel materials and mixtures are to be tested for thermal stability. So, this indicates that the material which you are dealing with is not a very good material to resist 100 degree centigrade because there is a thermal collapse or instability. Now, this is the result of a typical fly ash which I have been showing you. So, most of the fly ashes they have calcium oxide in them and because of calcium oxide they will show you exothermic reaction. Now, if you are trying to use a mineral for your you know as a cosmetic what type of mineral you will use a mineral which shows exothermic reaction or endothermic reaction yeah it should cool for facial particularly ladies use is it not. So, you have to have a mineral when it comes in contact with water it should give you a cooling effect. So, all your Ayurvedic treatment they use the mineral where they take the heat from the body and they show you cooling effect all right. So, this type of mineral logic can also be studied by using this technique. Now, this project we were doing for pretty light industry by the way for designing their brand you know the brand which they make what is the name of the brand Fevicol. The biggest question is that why Fevicol should be studied what are the gradients of Fevicol. Fevicol has lot of minerals of clay elite or kaolin for that matter your Colgate toothpaste also has lot of kaolin is it not you agree or no. Now, the question is if you make a paste which cannot be squeezed out of the tube what is going to happen you get up in the morning you try to press it and nothing comes out. So, this becomes a very interesting problem related to rheology of minerals where we have to contribute to the society. Similarly, the minerals which are used for you know remediating the nuclear waste hazardous spaces so on applications are tremendous you cannot believe any glue which you use must be having a binding material as a mineral. So, this is where the mixing of minerals with the glue, rheology of the air, thermal stability of the paste, the type of you know color which you are adding to this, the type of perfumes which you are adding to this they should remain there becomes a big issue.