 To the session, High-Volume Fly Ash Concrete, HVFA, myself, Mr. Chetanji Kunapure, Assistant Professor, Department of Civil Engineering, Wolchen Institute of Technology. Now, at the end of this session, students will be able to understand the use of fly ash with higher volume in concrete, properties of concrete in fresh state and harder state for this HVFA. Construction practices and curing for high-volume fly ash concrete. So, let us see what is mean by high-volume fly ash concrete. And first thing is, a fly ash is finely divided residue resulting from the combustion of the powdered coal and transported by the flue gases and collected by the electrostatic precipiter. This is called as fly ash. Now, this exhibits pozzolanic behavior. Now, high-volume fly ash concrete is a concrete where a replacement of 50 to 60 percentage of cement is made with the usage of fly ash. That is why it is called as high-volume fly ash concrete. But our standard IS 456, which is a code of practice for plane and reinforced concrete, it allows only 35 percentage of replacement of cement by fly ash. So, the binding material cement that must be replaced by 35% maximum by our code. Now, what are the ways to use fly ash in concrete? First is mixing fly ash with cement linker at the factory or plant to produce Portland pozzolana cement, PPC cement, which is also called as a blended cement. Blending is with fly ash. Now, second thing is using fly ash as an admixture at the type of making concrete at work site. These are the two ways. Now, what are the benefits of using fly ash in concrete? First is low heat of hydration. So, we are reducing the quantity of cement. We are substituting the quantity of cement. So, as cement is used, heat of hydration will increase. So, fly ash, which is having low heat of hydration and thermal shrinkage. So, shrinkage problems of cement, heat of hydration, this is one more issue that can be reduced by using fly ash. Second thing is use of fly ash improve the resistance to attack by sulphate soils and seawater. So, sulphate soil which is reacting with or which is attacking the concrete that can be registered by this use of fly ash. Now, these are properties of fresh concrete. There are six mixes. First M1 is the mix which is having 0% of fly ash means this is plain cement concrete. And in which blending is not done. Now, 10% admixture is used in M2, 20% is M3, 30% is M4, 40% is M5 and 50% of fly ash is used in M6. So, this is percentage substitution in cement. So, these proportions are also given by weight for cement, fly ash, water cement ratio of the mixes, coarse aggregate, weight, sand, dosage of super pasteurizer. Now, you can observe here when we are studying the fresh properties, slump of concrete when only cement is used in M1 that is 100. As the percentage of fly ash is increased M2, M3, M4, M5, M6. Now, the slump is reducing you can observe here, 90 to 65, 65 to 40, 40 to 30, 30 to 20 from M2 to M6 respectively. And even the air content is also measured. Air content in OPC is 5.2% and as fly ash is increased, this air content is reduced. This means voids are reducing in the concrete in which higher percentage of fly ash is used. Now, even the temperature is also shown this is this temperature of the concrete in fresh state. So, there is not much variation for this mixes of M1 to M6. Now, density of concrete fresh, concrete density kg per meter cube. So, for the concrete having a cement only in 2308 and as percentage of fly ash is increased, the density is little bit increasing because fly ash is very fine powders which is reducing the voids, so the density will increase. Now, next thing the properties of hardened concrete when the concrete is set and it has become hard. Next properties are the strength properties. The first is compressive strength. You can observe here six lines for these six mixes. So, 0 percentage fly ash, 10 percentage, 20, 30, 40, 50 percentage fly ash. On x axis, age of the concrete is given in days and on y axis compressive strength. So, at 7 day, 14 day, 28 day, then 56 day, 91 day and 365 days the strengths are determined. As percentage of fly ash is increased, this compressive strength is little bit linearly increasing from 7 to 40, 14 day. You can observe here this portion. But after 14 days, even after 28 days, the strength gaining in the concrete which is having only cement is gradual linear. But when the fly ash is added and higher amount of fly ash is added, that gain of strength after 28 days is large. So, this variation is there. So, percentage of fly ash if it is added with higher extent, higher volume, even after 28 days the strength gaining continues. So, that second graph is a bar chart we can call here. So, here fly ash percentages are given on x axis and on y axis compressive strength is shown. So, different at different ages with different percentage of fly ash, the strength is designated. My interest is in 28 day this one. So, at 0 percentage you can see the strength here about somewhere 28. At 10 percent little improved, 20 percent, again little improvement is there, 30 percent, small improvement is there, 40 percent, small improvement is there. In 40 to 50, the difference is not much. It means 40 to 50 percent fly ash is giving near about same strength. Now, this is a flexible strength of concrete. You can see here again from 7 to 28 day, the increase in the gain in the strength is linear and again it is little bit continuing. This line indicates the concrete which is having 0 percent fly ash means only cement is used in this concrete. Now, next is 10 percent, 20 percent, 30 percent. Now, sudden variation is shown by this line. So, this line is 30 percent fly ash and last two are 40 and 50 percent. So, these two lines last two lines are 40 to 50 percent fly ash. So, flexural strength which is higher flexural strength is given by 40 percent fly ash concrete, 50 percent fly ash concrete and as age of concrete is increasing, this gain in strength is also increasing. This gain is there after 28 days. So, the same thing which we have seen in compressive strength parameter, the same thing is also here for flexural strength. You can again the graph is plotted in the different manner on x axis 10 percentage of fly ash are shown. On y axis, flexural strength is shown and these are the strength at different ages. So, 28 day is the point of interest you can see here little improvement is there and in 40 to 50 percent little bit the difference is very very small in flexural strength. Now, next is tensile strength because these three strengths are actually the strength parameter for the concrete. So, again the same variation is there. You can see this line is the concrete without fly ash only cement is used and as the percentage of fly ash is used or increased. So, the strength is more for the concrete which is having fly ash. Now, as higher percentage fly ash is used, the gain in strength is continued after 28 days. This is the actual additional advantage in the high volume fly ash concrete. Same thing is there in fly ash which is different percentage presented on x axis and split tensile strength on y axis. Same thing is there. Now, even the water tightness is ensured by using fly ash in the concrete because fly ash is very fine powder and all pores are filled by this fly ash. Now, which are the properties of concrete ensured by water tightness? This is the question for you all of you just think of that and write those properties which can be enhanced or ensured by water tightness just write down. Now, water tightness ensures resistance to corrosion, resistance to alkali aggregate reaction, resistance to sulphate attack and all these things will improve the durability. So, water tightness ensures these three parameters which automatically improves the durability of concrete. Now, the construction practices and curing. High volume fly ash concrete takes longer time to set, accelerating add mixtures used based on compatibility. This is one thing. Then this concrete mixtures do not suffer excessive slump loss in a short period. Now, with slabs, concrete surfaces must be membrane cured or by covering with the surface with a heavy plastic sheet. So, this is one issue because setting if it is very it is taking more time or longer time. So, definitely curing for the first seven days is important. So, minimums of seven days moist curing is mandatory in case of high volume fly ash concrete. So, moist curing is mandatory in this case. These are the references for the today's session. Thank you.