 been talking about characterization of geomaterials and this is where we have talked about need for geomaterial characterization, geotechnical characterization, mineralogical characterization, morphological characterization. The morphological characterization is also known as granular metering and there are a lot of people who are working in this area, very interdisciplinary subject and you will see now that this is a subject which is at the peak of its advancement both in terms of electronics and in terms of applications. So what I have done is intentionally I have included a lot of gadgets which are being used internationally for understanding the morphology of the soil grains. Of course this is valid for the coarse grain materials not for the fine grain materials where the life becomes very difficult. So by granular metering or the morphological examination what you intend to do is if this is the matrix of the geomaterial you have different types of particles both in terms of sizes, in terms of shapes, in terms of their surface features and then you want to develop a histogram to show how the particles are distributed in this matrix. And this is where the concept of soft scanning what is known as image analysis comes very useful and historically if you see that this is how we started our career maybe 20 years back there used to be a laser camera and a microscope there used to be a flat bed and on this flat bed you sprinkle some of the particles of the geomaterial and with the help of laser scanner you can see the morphology of the particle. For you information laser is a least scattering ray alright. So it maps the image of the particle in the precise manner. This is historic and now what exists in contemporary world is mind boggling just visit this site where you have different type of particle analysis systems which are available commercially in the market these are known as image analyzers or particle characterization. So gone are the days when people used to do only see analysis and they used to be happy. The type of questions you have been asking in the last lecture what all can be done once you have studied the morphological features of the particles you know lot of strategies can be developed and you must have realized from my discussion in the previous lecture that nowadays particles are being used for creating additional parking space on themselves in terms of adsorbents or catalysts. So what I showed you in the previous lecture is on the quartz ball of fly ash we have deposited by chemical process materials which are highly porous and which provide extremely high parking space for environmental parameters. This could be microbes, this could be cations, this could be water, this could be gases I can park on them at the same time what I can do is I can include these particles into the soil system so that they will have a tendency to extract all sorts of contaminants from the soils. So both ways you can use these particles. So this is a very interesting process which is basically geotechnical engineering centric but people from different walks of life and subject are utilizing this. So whenever you get time click over these websites and you can see this is the future of particle imagery. You have different types of systems which are available in the market and you can have different types of measurements, chemical identification, particle shape, contaminant detection, particle size, image analysis, morphologically directed Raman spectroscopy and everything can be done. Very expensive tools but very precise in today's R and D. Sometimes they also call as 3D or 4D imaging with respect to time also you can measure the processes. So this is the latest in the particle imagery right now. Some of the few gadgets which I thought I will show you which are being used for doing the nanometry or the particle size analysis and these sieves are not ordinary sieves these are 3 dimensional sieves which are known as ultra sieves. So when you come to the lab next time we can show you how these sieves work. These are also based on 3 dimensional motion of the sieves which is generated due to the vibrators located at the base of the sieve sets and the beauty of this type of systems is that you can do the sieving, try sieving in the range of 125 millimeters to 20 microns. 20 micron is mind boggling is it not because nowadays the research is mostly focused on the particles which are less than you know 4 micron, 5 microns, 10 microns which are the most active phase of the geomaterial which earlier has been ignored completely in conventional geomechanics. This is another interesting gadget which is known as IVZ 3D surface laser topography generator. So what you see over here is that this is a laser beam which is falling on a sample which is kept in a dish and then with the help of the laser beams I can do complete the scanning of the particles these are commercially available instruments. So if you click over here you can learn what these systems do this is ambivalent the name itself suggests that this is the IVZ or you know IVZ they call it. So it is a 3 dimensional microscopy where you can see the features on the particles. So most of the research is being done to understand the morphology of the grains of the sands. Sands are more a black box everybody wants to realize what are the features on the sand grains and so that I can utilize it as an engineering material and these are the ships in the subject. So you can see the surface irregularities, surface features, bio influences in the geomaterial typical type of processes which are happening on the surface, extrusions, you know different types of protrusions and all those things can be studied and as you can understand when you use a laser beam you can do a 3 dimensional sectioning also you can cut the sample photographically or tomographically and then you can study the features of the material. There is another interesting device which is known as LOTM which is being used and my students have used and we have published papers also and this is where we have utilized the concept of LOTM what is this known as is laser obscuration time method and if you go to the website of equipment it talks about you know I can see how the particle the entire particle can be mapped the way it falls in the water column. So in hydrometer analysis you are simply talking about the macro aspects the particle falling in the water column but here if I want to see the surface from all the sites and the features of the particles they can be captured very these are all tools for advanced characterization of geomaterials, geotechnical engineering is not so obsolete as people think by the way. This is the branch of so engineering which is quite advanced and keeping you know pace with the time how things are changing and how the whole applications of different concepts are becoming more and more demanding. The typical result of the laser particle scanning there was a time when my students used to sit down and they used to count 5000, 4000, 6000 particles you cannot believe, takes control volume of the sands and any geomaterial used to spread it on that laser particle scanning system and now you can see on the y axis it is mentioned clearly how many particles have been counted and what is their particle size. Very soon you will realize that there are lot of limitations of hydrometer analysis and one of my student Dr. Shanta Kumar he has published a paper in ASC where we have dislodged the concept of hydrometer analysis, we have written that should not be used and the simple reason is because you are allowing the interaction between water and geomaterial which alters the properties of the geomaterial and hence the results which you are going to get from hydrometer test are not realistic. So these are the shifts in the recent world where even particle size which appear to be a very, very routine and mundane exercise is becoming so intricate and the reason is very simple because the industrial applications have become tremendous and people are using this concept of packing of particles to create different type of objects. So if you sum up all these things you will get a table like this where you will get number of particles, then percentage of particles and these are fly ash of different types, GGBF as if you remember ground granulated blast furnace slag and the silica fume, silica fume is a very fine powder but even then we could do the soft scanning imaging and what you will observe is that most of the particles fall in the category of almost less than 3 micrometers where typically you would have like to use hydrometer but because of a specific gravity of the material you cannot use hydrometer because silica fumes are very light as compared to water so you cannot allow them to settle in the water. GGBFS the problem with this is you will realize very soon that this has self cementing properties it has lot of calcium oxide in it. So the moment it comes in contact with water it sets, it forms lumps and hence GGBFS can also not be characterized by using hydrometer analysis. Just look at the other properties if you see the specific gravity of the fly ash is could be varying depending upon their source and composition, GGBFS shows very high specific gravity and silica fume shows very low specific gravity but not the density, density is absolutely low. What I wanted to show here is that if you compare the specific surface area you will find the specific surface area of silica fumes is extremely high it is approximately 20 meter square per gram. Imagine it is a 20 meter square that is approximately 4.5 by 4.5 meter area per gram of the sample. So this much activity the material shows because of its inherent characteristics either because of the mineralogy or because of the surface features. How do we get rid of coagulation before counting the actual number of particles? You have to spread them as thin as possible, yeah so your point is correct so if you read Shantakumas paper you will realize that we have used some plastic balls to break the clodding of the particles and that paper is published in ASC where we have shown the particles of admixtures which are charged like fly ash silica fumes even sieving cannot be done because the moment you do sieving these particles form clots. So you use some external materials to break these clots at the time of sieving. It is a beautiful paper characterization of fly ashes something written by Shantakumas in ASC general of materials. Now let us talk about the physical attributes of the particle physical characterization. So in physical characterization the most important parameter is specific surface area and because the specific surface area is the parameter which guides you know interaction between the geomaterial and the environment or even water so anything if it has to interact with the geomaterial the first thing which becomes important is the specific surface. So this is a very important parameter in normal geomechanics lot of efforts are being done to capture SSA of the material. Again this is a very high end equipment very sophisticated instrument which is known as BET nitrogen adsorption method why nitrogen gas is being used because this is non-wetting fluid non-reactive fluid and the basic concept is the way you use picometer buttons. So you wanted to find out what is the volume of water displaced by a certain weight of the geomaterial alright and that is what you use to convert into specific gravity. The same concept is being used here rather than using water they use gases to interesting you know effects one is the molecular size of nitrogen gas is extremely small. So this can penetrate into the material into the smallest force. Same thing is in the non-wetting fluid alright. So basically you are forcing nitrogen gas to enter the surface and the pores of the particle and then from there you can compute what is the surface area of the material. I am not going into the details of these techniques because as and when you require you please follow the course or the procedures which are specific for an instrument. But in today's world everything is electronically controlled and life has become simple alright. The second method is what is known as EGME and this is absorption of ethylene glycol monoethyl ether EGME there is a excellent paper which is written by Dr. Dallin Ido he is a faculty member at IIT Delhi IIT Chennai sorry and he was the author of this paper and we have compared their different methods of surface area computation and we have shown which method is the best. So it so happens that when you quote coating alright of each particle of the geomaterial by using EGME it is a sort of a dye then EGME tends to give you the total surface area of the grains total means the one which is exposed to the atmosphere or environment and the second area is internal because EGME dye penetrates through the particle and it gives you the total surface area of the geomaterial. Read the paper if you are more interested in knowing how the entire thing is done. Another method which is known as methylene blue dye method so Mb is also a dye and this principle is same you mix Mb dye with the geomaterial of known weights and then put it for evaporation beneath an electric bulb. So electric bulb energy is good enough to accelerate the evaporation process of Mb whatever gets retained on the particle can be identified by using a sort of a spectrophotometer you must have used in your environmental engineering lab photospectrophic emitters. So I can calibrate for the known concentration of Mb dye and what remains absorbed onto the particle I can do mathematical you know computations and I can find out what is the surface area. More advanced technique of finding out the specific surface area would be Mip this is also in our laboratory and in our laboratory we follow all these methods depending upon the geomaterial as the name suggests the mercury is included in the particles at a very high pressure and this I will be teaching you separately also when we discuss about the pore size distribution of the geomaterials and mathematically I can find out what is the specific surface area. There is another one which is known as helium gas picrometer. Helium atomic size and dimension is much smaller than nitrogen also. So for extremely fine particles we try to use helium in place of water because of the density contrast and because of the non wetting fluid. So helium gas picrometer also gives you the surface area of the particles these are techniques which are being used. Yes please. One case we are using the lighter that is nitrogen or helium another case we are using mercury which is high. So completely different techniques gases cannot be compressed at high pressure because they are liquefied. So when you are applying pressures intrusion process. So when you are forcing a fluid to enter into the pores you have to take care of two things. One is pore structure does not get altered and second thing is the fluid which you are forcing in at very high temperature does not get liquefied. I hope you understand this. So these are different issues different techniques so depends upon what is your objective better read this paper by Dr. Dallin Ido alright SSI determination of soils and we have to compare all the methods for different geomaterials and we have established that which method is the best okay anything else. How do we classify it on which soil we have to do which method how do we know that. So the best thing we you perform all these tests on different types of soils and then apply logic which one gives you the correct result unfortunately in R and D you will realize very soon that there is nothing known as absolute test or absolute methodology. So lot of judicious thinking has to be done to make things you know approved by the international agencies because each of these methods would have their own limitations and their own pros and cons. So you have to understand all those things first.