 So, just to give you an idea about these are the XRF pallets, if you get a chance go to the safe and you can see how these pallets are done, these are small aluminium pallets alright, half of them is filled with the adhesive is all standard methods nowadays they will help you. So, half of this is filled up with cellulose and rest of the half is filled up with the material for which you are trying to find out the chemical composition. So, after this thing is done, you press the upper portion of the pallet, it becomes a concealed pallet, the whole thing is kept under a UTM of about 5 to 10 tons so that it becomes a homogeneous system between the material which you want to analyse and the cellulose and cellulose dries up later on. So, this pallet is inserted into the XRF machine which I showed you and then you can do the analysis. Just to give you an idea about what type of calibrations are done before you can use the results, there are two types of calibration which are done physical and chemical calibration of the machine. Fortunately chemical calibration are standards, so these standards you have to buy from the market and you have to take along with you for doing the analysis. As I said XRF analysis gives you elemental composition, this is the first time we are talking about the elemental composition. This elemental composition could be of soil, this could be of admixture, this could be of any geomaterial. So, if you look at this, the way we read the value is percentage by weight of the material. So, different type of geomaterials when they were analysed, these are the results. Any lab will give you these results. The problem starts once the results are in your hands and how we are going to use them. That is where the entire catch is and unfortunately there is no guideline for that because I am sure that even if I write a book on how to read cardiograms, I am not going to become a cardiologist. You agree because a lot of information, judgment is required and mental thinking is required to eliminate the doubts and come to the right point. There are some quick analysis which I wanted to show you based on the XRF analysis would be. Calcium is the most important thing in most of the geomaterials, alright. So, if you take Israeli chalk which I was talking about earlier yesterday, the calcium present is extremely high as compared to any other material in this series. This is naturally occurring source of calcium. If you look at GGBFS, you will have very high value of calcium as 26.5 which is man made. So, now once you have understood the strength of the material, clear, you can utilise it. So, if I require a situation, if I want a material for a situation where calcium is required, what I will be doing? I will be adding GGBFS to this, alright, this is one of the strategies. I will not be using this material as a fill material where more silica is required. So, if you look at this material, you know sandstones, you have very high amount of silica, alumina, iron and so on. So, depending upon which industry you are running and what is your professional activity, what are your interests, this information can be used. So, some question you are asking few minutes back and I said hold on, why because I wanted to show you this. So, if you are looking for a material which is inert, crystalline, if you could fill material for the foundations, you should be selecting something which is going to be having lot of silica into it, correct. This is a poor choice because here silica is not much, it is an aquifer. So, if I am in, let us say industry where I am trying to develop zeolites yesterday, we were talking about zeolites, conversion of silica into zeolitic material. Normally, we talk about alumina silica ratio. So, if alumina silica ratio is of certain value, then only the material can be zeoletized. So, I have created another application of the material, I realize it. So, this is how the strategies have to be created. So, coming back to the simple things, if you add alumina silica iron and if this happens to be more than 70%, there are some classifications of the fly ashes, these fly ashes are supposed to be inert systems, good fill material. However, if fly ashes are not having alumina silica iron much around 20-30%, but calcium is very high, it becomes a cementitious material. So, an industrial waste, the moment you do XRF analysis, chances are that about 80-90% strategy of utilizing it can be created immediately and that is the crux of the discussion. So, just by doing this simple analysis, you can realize what I should be doing with this material. Another question could be if you cannot do something with the material, how to do it, how to augment the properties. So, all these concepts which are nowadays coming in medical sciences particularly, silica implantation, different types of artificial bones creation. So, from where you will bring calcium, there must be a process where I can do segregation of silica from the inert systems, I can precipitate it in a solution, I can make it hyperactive and all. So, these are different industrial processes, I hope you are realizing. Just to show you quickly how this ICP unit looks like, earlier days this used to be the situation, historic and nowadays everything is very compact, I will show you this is how the contemporary ICP looks like and very compact systems, you can install them in the laboratory and a lot of literature available on ICP and ICP-MS. So, when I was dealing with the projects from the atomic industry and particularly from BARC, atomic energy regulatory board of India, then I used to use ICP and ICP-MS quite a lot to detect how much portion of the radioactivity has been solved by the soils and how much is released and so on. These are very interesting gadgets, atomic absorption spectrophotometer you might have used in your environmental engineering lab to find out the concentration of contaminants up to PPM levels, part per million. But when you are looking for parts per billion, parts per trillion, then you have to do ICP analysis. This is how the gas chromatograph looks like with high resolution mass spectrophotometer. As I said, environmental geomechanics relies heavily on, in fact the practice of environmental geomechanics relies heavily on these gadgets. These are the tools which will help you in identifying the problem. This is how the FTIR looks like, this is Fourier Transform Inferred Spectrophotometer spectroscopy and then NMR. We wanted to do some experiments by using NMR at in one of the universities in France. This is the place where most of these facilities are housed in IIT Bombay, it is known as SAFE, Sophisticated Analytical Instrument Facility and this is worth visiting. But these are the latest development since last 5, 6, 10 years, this is what is going on. PH Determination Mination is a simple thing. I am sure you must have used it in the environmental engineering lab. We have a water quality analyzer, different type of electrodes which can be utilized as glass-calomal electrodes you must have used for finding out the PH because when the reaction takes place between the geomaterial and the environment, water or any contaminant, you would like to see how PH alters. So the way the PH of the body changes, you know, similarly the PH of the system changes, soil contaminant system and that becomes very problematic many a times. So most of the industrial byproducts are at different PH values either they are highly acidic or they are highly basic. So the question is how would you neutralize them, how would you create a synergy between the soil and something which is quite aggressive in its PH value. So these type of thoughts people are having and a lot of research is being done. Jasmine is working on a project where we are trying to neutralize, you know, highly basic industrial byproducts where the PH is 12, 13 by injecting gases into it. In this trial, we are doing the laboratory so that the whole thing can be injected at one of the heaps in the real life. So we will have to design a complete piping system, drainage system, we have to force gases to go inside and complete mathematical modeling. So you must be aware that for determining PH, we dissolve the soils in water at different L by S ratios, liquid to solid ratio and then we measure it and these are the parameters which you can obtain. You can obtain the PH, the temperature, the TDS, total dissolved solids, electrical conductivity and now it is in our profession, this oxygen demands, BOD and CODs are becoming very important. You see when I was a student, I never thought that these things are going to be a part of geotechnical engineering, but sometime back I gave you an example of my student thesis, Dr. Sushmika Sharma who worked on these sediments from the different water bodies and sedimentation tanks which had apart from chemical activity, the pathogenic activity also. So there we realize that COD, BOD are going to be very important for the sediments also because they add up to the kinematics of the system. So whatever you do not think today becomes a part of the mandate which you have to take for surviving tomorrow, all right, this is a simple thing and maybe that is what R and D is. So you have to keep on moving with the concepts and the problems with society is facing, it is okay. This is the cation exchange capacity which you are talking about. So and one of the ways to characterize soils would be the best way would be it is easy. So if you see our papers which we have written, we have created a soil classification system based on SSA and CEC and this is a published work by Sushalakshmi and I think Dr. Srinivas Kadali. So for us if cation exchange capacity is known, nothing else is required, why? Because cation exchange capacity includes in it the physical properties attributes, the chemical attributes, mineralogical attributes and all sorts of other attributes which otherwise you will not be able to detect. So I can say that cation exchange capacity happens to be a parameter which is the holistic representation of the material. Now the question is how would you obtain this? So there is a code IS code 2720 which describes this method. As I said this is a base exchange process. So you take the soil, allow its interaction with a calcium solution mostly calcium chloride of certain concentration. So when you are allowing interaction between soil and calcium chloride, all the calcium ions will get adhered on to the soil particles, they will replace sodium ions, you agree? Because the yeah because the valence of the calcium is 2 and sodium is only 1, clear? So higher valency replaces a lesser valence. So this is the first cycle, then what you have to do is after this interaction is over you wash the soil sample with sodium acetate. So what you are trying to do? Now you are trying to see whether sodium ions can displace calcium ions which have got adhered on the soil particles or not, clear? So this process has to be done several times, it is an intricate process. So when you do this process at the end of it, if you can measure the concentration of calcium ions, equivalent weight of the cations, weight of the sample and what is the volume of the solution which you have taken, it is a simple titration. This gives you the cation exchange capacity, this is the answer to your question, clear? Please read the published papers by anybody from my lab because for us CEC is the starting point. So we do not talk in terms of size of the particle and its mineralogy separately, what we do is we define the potential of the material to interact with the environment based on its cation exchange capacity. And just as a quick match of numbers what you will observe here is I have given you a sort of an application of how cation exchange capacity can be utilized to decipher the characteristic of the material. First of all, you should realize that the units of CEC are milli equivalents per 100 gram as per standard. What you will observe here is that senospheres are exhibiting extremely less value of cation exchange capacity. Yesterday we discussed that senospheres are the quartz balls. So quartz is the least reactive material, alright, fly ash is by virtue of having some chemical adulteration in them might show you a bit high cation exchange capacity. For the maximum cation exchange capacity comes in the soils, the CEC is a normal silty soil where you get very high value of cation exchange capacity and chalk where also you have high cation exchange capacity. So these are tentative numbers but these tentative numbers tell you how reactive the system could be. So sometime back I was talking to you about spillage of activity, nuclear activity because of a disaster and that spillage took place on in the water body and from water body it came on the beaches and the sands and the soils got completely contaminated. So at that time some people contacted me that can I create a material of a certain CEC value. So imagine the similarity between the cements which are being sold in the market, you have a grade of the cement, is it not. Now people are asking that can you create the soil of a certain grade, are you getting the, are you realizing what is happening in the international market. So you might be very lucky to have a certain mineral in your country but that mineral might not be available everywhere. So can you convert or can you alter the existing minerals to a level which becomes a medicine or which becomes a commodity for industry. So this is where a lot of processes are being done and the SEMs which I showed you in the previous lecture were on the quartz balls, you are having some depositions either because of zeoletization or because of you know agglomeration of the particles which I showed you when you do dual gas conditioning, flue gas conditioning. Ultimately what happens is the CEC gets enhanced. So this becomes a precious catalyst for me and these all catalysts are created by human beings. Hope you have understood the whole thing, yes. Celica fumes, their specific surface area was very high. So it was used to be, it should be highly reactive so that the cation exchange capacity of Celica fumes will not be high. So you must have realized as I have been repeatedly saying that you know what happens is because these are all gravimetric processes. So if you are adding a material to liquid where it floats in it, you are defining the concept of titration or concept of gravimetric analysis. So unfortunately Celica fumes, cation exchange capacity cannot be obtained by this method because the moment you make a solution out of it, they will only float, alright number one. So if you have to find out cation exchange capacity of Celica fumes then you have to use some other method and that would be SSA based. So if you see the papers which are written by Sushalakshmi and Srinivas Kadali where we have come out with generalized relationship between different parameters which are used in conventional geomechanics. And we have related all these parameters with SSA and CEC including liquid made plastic limit, shrinkage limit and specific gravity also. So my idea was to get rid of the conventional scheme of classification which is partial, which is not holistic. It takes into account only physical attributes and replace the entire thing with something which is more holistic. So this is what the state of the affairs is right now. One more question which might be linked with this discussion is, suppose there is a microbial activity which is harping in the soil mass of the geomaterials, what will happen to the cation exchange capacity? So in our opinion, any process which occurs in the geomaterials can be monitored by a regular sampling of the material and checking its cation exchange capacity. So if CEC changes, that change is because of some mechanism and then I can trace back that is because of what? So this is the present and future of the subject. Hope you have got enough ideas. Just to touch upon the microbial characterization, read the papers by Sushalakshmi, Dr. Somya and Meenu and Asha, these are my students who are working in this area and we have published very good papers on microbial characterization of geomaterials from where the subject on biogeo interface started. This is a paper which I am referring to state of the art on geotechnical engineering perspective on bio mediated processes. If you read the introduction of this paper, you will realize that we are absolutely anti-Tazhagan geomeganics and why we are saying that all the concepts should be dry clean. So you have to read the entire paper to understand that why is such type of tones we have acquired in the process of doing R&D. And this is the slide which I have taken from Shashank's thesis, if you remember. This is the microbial activity which is harping in the soils and which cannot be ignored, different type of bacterial growth, microbiological growth and this is the harping of the biological activity on sands. So we were talking about biosoption, bio suction, bio CEC and so on. This work is still ongoing, but very interestingly this concept started with one of my consulting projects where nobody was able to define the cause of failure of a huge piled draft system. And this piled draft system had been under severe distresses and the company was unable to start up their process. So mechanistically everything was absolutely alright, but even then the settlements were occurring. So that is the time when these thoughts came to our mind that let us take samples from as deep as 40, 50 meter where the pile tips are resting and do some microbial analysis, examination and then we realized that there was a big microbial effect on the stability of the soil. This is how this subject started. But did you find any evidence regarding that draft settlement with? Oh yes, so we ultimately linked everything to the microbial activities. So the whole dimension of the project got changed, then adequate precautions were taken to not let microbial activities survive at that particular depth. From this point onward the decay of the material also became a major thought in our research process.