 In today's lecture, I intend to talk about geomaterial characterization and the sub topics are need for geomaterial characterization. I have emphasized upon this several times that why do we require characterizing the material particularly geomaterial the soils and rocks or the waste form of the industrial waste. When we talk about geomaterial characterization the first topic is geotechnical characterization, mineralogical characterization that is how to determine the mineralogy of the material. Next is morphology particularly dealing with the shape of the grains and the size of the grains physical characterization which most of the time you have already done it. You are aware of how physical characterization is done. Chemical characterization some part of this you might have covered in your undergraduate. This is where we will discuss about pore solution sampling how the pore solution is obtained from the soil sample. Application of pore solution sampling would be in determining corrosion potential of soils or the geomaterials and this also falls in the category of chemical characterization followed by this option-disoption test which described the reactivity of a geomaterial with environment or contaminant followed by thermal characterization of geomaterials and lastly the electrical characterization of the geomaterials. In today's lecture I would try to finish the physical characterization part and then most probably in the next lecture I will be talking about the chemical characterization. Now, what is meant by geomaterial characterization? The first letters are not coming here it seems the physical characterization, the chemical characterization, mineralogical characterization and thermal characterization. So, basically what we want to do is we want to study how these things influence the geotechnical properties of the material. Till now whatever we have discussed in this course you must have understood the point that definitely all these properties are going to influence the material properties how they are going to you know exhibit their response in the nature. So, this is where actually we will try to understand how physical, chemical, mineralogical, thermal and electrical properties are going to influence overall geotechnical engineering properties. Now, why this topic is becoming very important these days? It is becoming very important these days because of most of the times when we deal with hazardous and toxic waste particularly radioactive waste. So, this is where the basic question is how to design the buffers for waste and when we say buffer these are the materials which will be acting as a retardant to the activity of the waste. Now, when this material comes in contact with the waste which is having attributes of atomic waste in terms of its radioactivity, temperature, concentration. A phenomena which is known as thermo hydromechanical phenomena becomes very important and in present day scenario most of the laboratories and most of the researchers are working in the area where they are trying to see the response of geomaterials under thermo hydromechanical situation. That means how hydraulic properties and mechanical properties of geomaterials change when the material comes in contact with thermal fields. So, this is a very good research topic in present day scenario. Most of the research groups in western world they are emphasizing on these type of models, but you will appreciate a point that to study THM model you should understand how material is going to behave under different energy fields which we have discussed earlier. So, let us start with the geotechnical characterization. Most of you are aware of what is the significance of geotechnical characterization, what are the attributes of this type of characterization. The first one is we would like to study what is the void ratio and porosity of the geomaterial. Because this is the gross property which helps in understanding the response of geomaterials towards permeation of a flux that is the water or the gas or whatever. This is the fundamental property of the geomaterial. Then we try to study the compaction characteristics by doing proctor compaction, modified proctor compaction and so on. Then we talk about consolidation and compressibility characteristics of the geomaterial. The next is hydraulic conductivity and shear strength parameters and this is followed by a parameter which is known as collapse potential. I am sure that you must have done some test while doing consolidation and compressibility characteristics of the material to determine collapse potential of the soil. Now, this parameter becomes very important in your analysis particularly when you are working on soils which are highly compressible and which may collapse because of inundation due to water or exposure to the water or pooling of water let us say. Normally the collapse potential is defined in terms of delta in the void ratio divided by specific volume that is 1 plus E naught and this term is always in percentage. Now, to understand this phenomena you can consider this figure where the void ratio is plotted with respect to the effective stress. Now, if you do a conventional consolidation test your void ratio versus sigma prime curve would be a non-linear curve. So, as sigma prime increases void ratio decreases, but suppose if I decide a pressure or sigma prime at which I am allowing material to get flooded with water in that case what is going to happen now this is what is known as inundation. That means, you flood the system with water and particularly when we talk about collapse potential the starting point is the dry soil mass you pack it in a consolidometer ring and then apply certain normal stress. At this sustained loading if I allow water to go into the sample what is going to happen there will be a sudden drop in the void ratio and this is what is known as collapse of the material. Now, what is the practical application of determining the collapse potential can you can you tell me can you guess that what will be the best possible application of this type of philosophy. You think of a situation where the waste has been piled up near the some industrial activity or near a mine and then what happens is this waste has been piled up in a loose form and then comes rains clear. So, what is going to happen a system which is packed to a loose form when it comes in conflict with the water or gets flooded with water the entire heap may collapse. So, this is where these type of test can be simulated very easily in the laboratory. Now, this is one of the examples of how waste environment interaction can be studied as far as structural properties are concerned. Because this collapse is nothing, but a structural collapse clear. So, if you know the initial void ratios and if you know the final void ratio after inundation you can work out what is the susceptibility of this material towards collapse. So, this parameter becomes very important when we design heaps or the landfills is ok any doubts yeah collapse potential is always defined for a given normal stress. So, incidentally what will happen is that you see normally if you plot E versus sigma prime this is a normal consolidation graph. Now, if I want to find out for a given embankment which is of height h I can compute the sigma prime value which is nothing, but gamma into h and some factor. Now, if I inundate at this point and I will sustain the loading what is going to happen this system is going to collapse like this. And then if again I continue loading the system this is what the response would be. I can do further I can apply inundation somewhere here. Now, what has happened the system will collapse like this and will continue like this. If I sustain this point what happens this is the collapse of the material and so on. So, if you consider C p 1 C p 2 and C p 3 which are nothing, but the collapse potentials I think you can understand that for higher sigma prime the collapse potential keeps on decreasing alright. So, this is a good example of how you can design your systems for sustained loading. So, this is what most of you would be dealing with when you design your landfills or the disposal systems particularly when stacking is in dry condition is this any other question. So, most of you are aware of how to characterize materials by you determining its geotechnical characteristic. Now, let us study how to find out the mineralogical properties that is mineralogical characterization. The most important and useful tool or device or methodology would be to conduct X R D that is X R D fraction. I have shown here a setup where X R D machine is shown the setup is available in our institute at SAF and in metallurgy department department. So, we take help from them to determine what is the mineralogical composition of a material which is known as X R D. So, essentially what happens is that you have some beams of X-ray which is which are falling on the sample and then whatever diffraction is obtained can be obtained by using some receiver unit. The second tool which is used for determining mineralogical characterization of the material is a scanning electron microscope which is SEM all right where you can find out the composition mineralogical composition of the material in the best possible manner. A typical result of mineralogical characterization is shown over here for different materials which I have included in my today's presentation. These materials are a C S type of a soil which is known as a silty clay, a white clay which is nothing but pure kaolin, some chalk samples in Israeli chalk, red sandstone, brown sandstone, different fly ashes, senospheres of different types and GGBFS or the blast furnace slab. Now if you look at the X R D analysis or X R D patterns which are also known as X R D defectograms you will get something like this you must be noticing a lot of peaks. Normally X R D is conducted by using a filter this case filter was copper K alpha. So, copper K alpha is the filter which is used for doing this analysis and we use the angle 2 theta where theta is the angle of incidence with respect to normal of the X-ray beam. So, normally this analysis the scanning of the sample is done from 10 degree to 100 degree and depending upon the minerals which are present you will find different types of peaks here. So, each peak corresponds to a particular theta angle. Essentially what you are doing is if you know the radiation source or the filter source you know the wavelength of the wave all right and then by using Bragg's law that is 2 d sin theta equal to n lambda if you remember. So, where you can find out the d value and d is the spacing between two atoms. So, this way you can work out the value of d which happens to be a characteristic value for a given mineral is also known as lattice structure. So, corresponding to a particular theta what you can ascribe is you can ascribe a particular mineral like in this case m, m corresponds to mulite, q, q corresponds to quartz and so on. So, whatever minerals are present you may get a picture of these minerals in the diffractogram. Now, the question is how we are going to read this diffractogram or reading this diffractogram in today's world people use JCPDS files. Now, JCPDS files were given by the powder diffraction center which is located in Pennsylvania USA. So, material characterization lab and they have come up with standards different type of standards. So, this is a CD ROM on which all the minerals are listed with d values. As I said d is the spacing between the two adjacent atoms of the material. So, this way you can identify up to fourth decimal place the value of d and that value is corresponding to a particular mineral. Now, what else you find the difference between this figure, this figure and this figure. Can you differentiate between one, two and three figures? Yes, one is the height of the peak. Clear? That is not very much important in excess diffraction analysis. Do you find any other difference? Correct. So, here you will find a band. Now, this is what I have been talking about sometime back that depending upon the phase of mineral which is present in material you can define its activity or reactivity. The basic difference between one, two and three is you have a less peaks is it not. However, in these two cases you have lot of peaks. So, what is the significance of this? Each peak corresponds to a crystal. That means, each peak corresponds to a crystalline phase. So, a material which has more crystals, more crystalline phase is always going to be less reactive. It is a passive material. However, if peaks are less and you get a band it shows that this material is going to be highly reactive because here alumina silicates and other minerals they are present in glass form and glass also can be crystalline as well as amorphous. So, here the glass happens to be in the amorphous phase. So, this phase of the material is highly reactive. So, the moment you put water into this or the moment interaction between water and this material takes place immediately the gel formation takes place. So, when you are making concrete which material you will prefer out of the three? Third one. Third one. So, incidentally this corresponds to GGBFS that is blast furnace slag. So, blast furnace slag we will see further that why it is used as a replacement material for cement. But the first trait is the mineralogically this material happens to be quite active because most of the minerals are present in a amorphous phase not in the crystalline phase. So, this is how you can differentiate between the materials immediately and then once you have differentiated the material you can use it for a specific purpose. So, suppose if I give you different materials and if I ask you to select materials which are the right candidate materials as a backfill material and the right material for replacement in cement so, which type of material you will use as a backfill material and which type of material you will use as a cement replacement material out of these three. So, first and second becomes a good material for filling or land filling back filling raising the foundation platforms and so on. So, if you want to construct embankment out of the fly ash clear. So, this I hope now you it should be clear to you that how easily you can define and use the material for a specific purpose is it for clear. I have tried to give you the maximum possible information analysis wise and based on this information immediately you can say that this material is best suited for this purpose or not. Yes, Sushit has asked a very good question that this is basically a qualitative way of defining the minerals which are present in the material. Now, is there any way to quantify? Can you guess is there any method to find out the quantitative value of the mineral which is present? For that what you have to do is you have to take the purest form of the mineral do XRD and superimpose XRD diffraction pattern on these graphs depending upon the relative magnitude of the peak which you are getting that is a relative intensity. You can define depending upon 100 percent peak length in the pure mineral and the height of the peak in this case you can find out what is the percentage of the mineral present. So, this is how you can quantify the amount of minerals which are present in a geomaterial as well. This was a good question. So, this type of analysis we are using quite a lot in our study to differentiate the potential of the material for a specific purpose. Now, here I have listed some minerals which are present like anorthite quartz, montmoronite, in white clay normally which is nothing, but elliptic type of a soil or kaolinitic type of a soil, calcite, clenoptile, opal ct, elite and so on in chalk samples. These are the chalk samples which we had got from Israel and they are the best possible acupers. Their porosities are approximately 38 to 40 percent. So, in our studies you are using samples collected from Israel is known as the Zali chalk and then you are trying to study the response of the Zali chalk with respect to our own materials like red sandstone and brown sandstone. In typical fly ashes you will find quartz, molyte and hematite. Hematite is a compound of iron. Then I have used some senospheres where we have pure quartz and molyte. Incidentally if you can recover these senospheres you can do lot of industrial applications with them particularly manufacturing good dielectric material. So, these are purest form of the quartz which is normally used in a dielectric material in your chips and electronic circuits and electronic devices. You must be noticing here that for GGBFS I have written glassy phase. There is no crystal present except for the glassy phase and that is the reason it is highly reactive. So, is this part clear that how based on simple XRD analysis you can differentiate the material and you can at least suggest some possible usages is this ok. Now sometime back I had been discussing about activation of the fly ash samples. If you remember I had shown you some slides where fly ash got converted into a zeolite. So, how would you say you know with lot of inaffirmative that something has happened to the material. So, if you compare the XRDs of the original and activated ashes what you will notice is that quartz is present in both molyte is present in original and activated ash. However, in activated ash there are two more minerals which are available these are known as NAP1 zeolite and addoxyl sodalite zeolite. Sometime back I had given you an idea that you can work on SRT, what is SRT? Silica Reduction Technology where you can reduce the silica from the geomaterials and you can increase the components of alumina and iron. Now any guess how would you do SRT analysis? I am sure you will appreciate this point that if you have different XRDs of the samples at different stages of silica reduction you can make out very easily that whether your process of silica reduction is effective or not. That means, the content of quartz and molyte should be decreasing in the activated ash and content of zeolites should be increasing in the activated ash. So, this gives a very broad picture of how material characterization can be done based on XRD analysis. Is this part clear? Any questions? Oh tics means they are present cross means not present absent or two means most prominent. So, two tics correspond to most prominent phase, one take corresponds to present cross corresponds to absent and this corresponds to presence only. So, this type of treatment was with the help of sodium hydroxide. The second characterization scheme which is normally used is scanning electron microscope or microscopy. These are the scanning electron micrographs of original fly ash sample where you can see perfect balls or spheres which are present. There are some senospheres, hollow spheres, broken spheres which are present in the ash. It is an interesting word of fly ash you know. So, the more and more research you do the more you get involved in this difficult to come out of it. At the same time you may find lot of carbonates also present you see. So, this type of analysis takes lot of time you have to sit down patiently and study the micrograph and see what type of information you can get from this material. So, that you can use it accordingly. One more thing you must be noticing here that some numbers are written here is not like this number. So, this corresponds to 550 time magnification. This is 20 kilo volts that means the energy of the light which is being you know thrown on it is 20 kilo volts and then there is a line. So, this line corresponds to 10 micrometer scale. So, this much information you get. So, if I use this scale I can find out the size of the particles or the grains which are present in fly ash. It is very scientific. So, you can have more and more information coming out of this. Interestingly, if you are using an electron probe you must have used I am sure in geology. Have you used it? So, what happens if I use the electron probe along with SEM exactly I can find out or I can ascertain what is the elemental composition of each particle just by using some electron probe. So, well this is the photograph which I have already shown you of the activated samples of the ash where some growth is taking place. So, this was also ascertained with the help of scanning electron microscope. We could not do its electron probing because that time it was not available. Otherwise we could have estimated the elemental composition of the coating on each particle that would have been the wonderful thing. Some of the typical SEM micrographs which I thought I will show you in this lecture of different fly ash as are you do can you see a typical shape over here. So, sometimes you have either a medler type of a structure or flaky structure also available in the fly ash particle. This is a very interesting photograph. Can you make out something from here? Apart from that I hope the picture is clear on the screen. Doesn't it look like a nest inside you have eggs being laid by a bird. You can see small small particles entrapped in this nest. Is it not? So, this is a peculiar type of a structure which you find in some of the ashes which are known as chlorospheres. So, these are the broken spheres in which there is a particle of ash got entrapped at the time of formation. So, the question is how ash is formed? It is nothing but the at very high temperature the ash particles might have got molten or melt. It trapped lot of particles inside and has got frozen. Now, geologists will use this type of slides for finding out the composition of different minerals which are present in the rock which is known as spectrographic examination. So, you go for thin slides and find out the mineralogical composition of the rock mass. You can find different type of structures here you know some big units small perfect spherical units small small particles of different shapes and so on. Look at this a beautiful assembly of particles is it not? Now, this was artificially created by Dr. Shantagumar. The person who finished his PhD recently I will show you why you are trying to do this type of growth of the particles on the fly ash. I hope you will appreciate this. This is intentional see what we are doing is a arrangement of the finer particles on bigger particles. So, bigger particles are being used as seed and on the seed we are growing something. Where can you use this type of system in geotechnical application? Yes filters where you can grow something in the micro pores. So, what happens? The entire pores get locked and then you get the best possible durability. Actually he was working on agglomeration of ash particles due to flue gas conditioning. It is a new concept in which we worked sometime back. What we wanted to do is we wanted to create a flock of the ash particles for improving the precipitation process in the boiler units. So, that no fly ash particles should go into the environment. Now, this is what is known as SPM reduction suspended particulate material reduction in the atmosphere. So, if you are going to work in a power plant nobody is going to allow you to throw the emission or the fly ash into the environment. So, this is where there was a need to develop a technology by which we can capture all the finest possible airborne ash particles and precipitated them. So, this is how the agglomeration was achieved with the help of dosing the gas the flue gas which comes out of the chimney with the help of ammonia and sulphur trioxide. So, this is known as ammonia conditioning and sulphur trioxide conditioning and then you can form different type of structures you know what happens. The moment this type of flock is formed it will precipitate down easily in the boiler unit and nothing will go into the environment. I hope you will appreciate that it is a very interesting idea where you are capturing the finest possible particles making a matrix it becomes big in size and ultimately it settles down in the boiler unit itself or the ash collection unit. Just wanted to show you how agglomeration of the particles can be studied with the help of advanced techniques like scanning electron microscopy. So, you generate a hypothesis and you can prove your hypothesis by going into the microstructure of the material curtsy advanced technology which is present these days like 7, 8 years back it was not really so possible. Here you can see lot of you know ammonium carbonate which is getting formed and the white color and the gray colors are of the ash particles. So, again you can get lot of information particularly if you are using a electron probe to determine the composition of each particle and what type of substances getting formed during the process. Any questions here? Any question? Sorry what extent would be the extent of agglomeration this is what your question is? Well we could not quantify the agglomeration process what we have studied is how ultimately the agglomeration is taking place, but yes your question is very valid and my guess is that agglomeration phenomena will depend upon lot of things particularly the surface charge, then the size of the particle, then size the type of the conditioning agent which is being used the structure of the ash particles and so on. So, if you do a very systematic study you can define what is the uptake capacity of ash particles that means how many finer particles each ash particle will uptake on it. So, this requires lot of fundamental study please be louder. Good this is again a very good question on which we have published two international journal papers. I wish you had asked this question three years back. We have shown that there will not be any difference in the ash properties. So, this paper is going to come in the ASC Journal of Materials. It is already in the print where we have shown very systematically there was a question asked by the users they were not collecting ashes from the power plants because their hunch was you are conditioning them with some chemicals and ultimately the properties may change and these properties may not allow this material to go into the construction material. So, we have shown that first of all the dosing which is done is very very small in terms of its magnitude or amount. Another thing is the whole concept of dosing ashes you just want this agglomeration to take place no mineralogical alteration is going to take place no chemical composition is going to change and no other properties are going to change. Interestingly if you put this material in water again disintegration takes place and all the particles will disintegrate. So, it is a sort of a temporary system by which you are trapping the particles by making a bigger flock. Because of this reason many power plants are unable to sell their fly ash because at on one side they are they are using flue gas conditioning to trap most of the fly ash which has which is trying to go into the environment. But then on the second side the question was whether this ash will be suitable for construction material or not. So, it is a real environmental engineering problem and civilian problem where lot of consequences are seen it is any other doubt sorry please speak loudly. Yeah this is what is known as flue gas conditioning that means you are adding either sulphur trioxide or ammonia in the gas fumes or the stack of the chimneys. So, this gas is responsible for creating a sort of a physical alteration and depending upon the surface area and the surface property of the ash particles this type of process will take place. So, lot of electrostatic concepts are involved in this and lot of you know chemical concepts are involved in this. So, truly speaking these type of problems are studied by chemical engineers, but because our interest in fly ash and its application in construction material we entered into this field. A good study would be you do these type of studies using SEM and then trap the fly ash which is going out of the stacks or the chimneys and then match the results of the two. So, what you will notice is there will be a drop in the particle sizes which are emitting into the environment because of this process. So, both of them are going to complement it to each other and this way you can show the efficiency of the traps or the back filters normally which are designed for safeguarding their environment against emission of pollutants in the environment. It is a big technology right now only one company in the country has a technology available with them. So, they design back filters for different emission units for cement plants, fly ash, power thermal power plants and so on. It is a good research idea and then another question would be how to increase the efficiency of agglomeration further because there is a limitation to this method. So, that is where you have to study the effect of electrical field and chemical field put together on the dynamics of the ash particles in an electrostatic precipitator all right. So, this type of modeling also should be done well just to give you some feeling of we have been talking about silica fume and GGBFS how do they look like. So, this is the particle of silica fume what is your observation here how do they look like. If you remember I had said that silica fume is a highly carcinogenic material it gets airborne very easily why it is so look at the shape of the particles. Surface area is very high that is right and you have lot of furs you know which make it very light because air entrapped in this system is much more. So, specific gravity is very very small very less 0.6, 0.7 and because of very high surface area if this thing goes in the lungs what will do it will absorb more and more moisture from the lung and that portion of the body or the lung may become cancerous. Now, the second group of figures these two are for GGBFS sometimes is also known as BFS that is blast furnace slag. The full form of GGBFS is ground granulated blast furnace slag. Ground means you are basically making it a powder in the granulated form as a blast furnace slag. So, this is how this slag looks like as all sorts of a regular shapes, but very highly reactive material why it should be so reactive go back to XRD. Amorphous form. Amorphous form that is right plus another thing when we talk about chemical composition then I will show you that why they are so reactive that is ok.