 Pumpable concrete, this is Mr. Chetan G. Gunapur, assistant professor of department of civil engineering, virtual institute of technology, Solaapur. These are the learning outcomes. At the end of the session, student will be able to explain the design consideration for pumping of concrete. Now let's see what is made by pumpable concrete. So as an introductory part, the concrete which can be pushed through a pipeline is called as a pumpable concrete. Now pumping means the concrete must act as a fluid or it must pass as a fluid through the pipeline. So concrete is made in such a way that its friction at the inner wall of the pipeline doesn't become very high so that it can move smoothly. It doesn't wage while flowing through the pipeline and pumpable concrete emerging from a pipeline flows in the form of plug. So let us see the process of concrete pumping. This is the diagram or figure one in which concrete flow under pressure is shown. The references or sources given here. You can see here pressure is applied to this concrete mass and at these two inner walls surfaces concrete moves as a plug and these are two lubricating films. And if the lubricating films are there then the friction will be less and whatever resistance is offered that resistance will be offered will be less pressure is applied and your concrete will flow. So these are two drag means forces which are creating resistance against this pressure. So the plug is separated from the pipe wall by a thin lubricating layer consisting of cement paste you can see here at these two inner walls. The pressure generated by the flow resistance must not be greater than the pump pressure. So this pressure must be greater than this resistance. So this will facilitate the continuous movement which is expected. Now next thing one more diagram is there or figure is here in which concrete saturated at very higher water cement ratio. If your water cement ratio is high probably that will be very fluid liquid. So in that case what happens in this diagram the pressure is applied here. Concrete with the higher water pressure for a certain pump pressure it may be such a way that water is forced out of the mix creating increase in the flow resistance. So water will flow out of this mass of aggregate and the fine aggregate will remain so the migration of this mix water will increase the flow resistance and this will lead to the blockage. So the possibility of the blockage is because of this phenomenon. Now concrete with lower water cement ratio it becomes very stiff and it will be very low workable. So low water cement ratio will give you low workable mix. Higher water cement ratio that will create or increase the flow resistance. So that we have to keep the proper water cement ratio. So this all this process in other words we can explain a very steep concrete is not pumpable and concrete with high water cement ratio is also mute pumpable. Now these are the design considerations for pumpable concrete. First is the proportioning of the mix is very important we should proportion our mix proportion of the aggregates fine aggregate cement as well as water so that it must be able to bind all the concrete materials together under pressure from the pump. Second is it also should avoid segregation and bleeding these are two nature segregation and bleeding of the concrete it may be pumpable may not be pumpable but these two natures must be avoided this is the regular problem in the concrete which shall not should not occur during pumping also. Now the proportioning of the mix must be able to deform while flowing through the bends. So concrete first generally for a small short length there will be horizontal pumping then it will be lifted vertically. So bend will be definitely there so the concrete must deform in such a way that proportioning is expected. So proportion of fine that is cement and fine particles below 0.25 mm size is very important quantities of the fine particles which I have just discussed regarding the cement and fine particles of the fine aggregate must be in between 350 to 400 kg per meter cube and this is necessary for the pumping. Now this above quantity is not only required for maintaining the lubricating film in the pipe but it will also require for quality and workability. So fines are very important from workability point of view and that will lead to give you proper pumpable concrete. Now these are the causes of occurring blockages. First cause water is being forced out of the mix which creates bleeding and blockage by jamming. So water if it is forced means just I have seen you when the higher water cement ratio is used and the water is migrating from the mix. So this will create the bleeding or blockage by jamming. Second is higher frictional resistance if your ingredients are or nature of the ingredients in such a way that it will give you very higher resistance. So in that case also there will be the blockages. Now let us see this figure which is expressing relationship between the cement content and aggregate water ratio. On Y axis cement content is there on X axis aggregate water ratio. So you can see there are two beds so nature is explained here. These are two extreme conditions also. If you go for very high cement content in the mix with the low aggregate water ratio probably you will get excessive frictional resistance. If you go for low cement content and very high aggregate water ratio you will get excessive segregation and bleeding nature concrete. So we should keep moderate cement content, moderate aggregate water ratio so that we can get the pumpable mixes. So this is just for the judgment this figure we can use. And if you go for in this region this will be the marginally pump will work at very high pressure if you go in this region so there will be a nature of segregation. Now my question based on the earlier figure. If the mix is having low aggregate water ratio and high cement content of the concrete what it will result in? The options are A pumpable mixes, B excessive segregation and bleeding, C pumping at high pressure and D excessive frictional resistance. So you pause the video think on that observe the figure and write down the answer. The answer is excessive frictional resistance D this is the answer. So you observe the figure then definitely you can use the nature of the concrete based on the aggregate water content and cement content. Now these are the important guidelines for pumpable concrete. Now we should use the accursed aggregate, natural aggregates which are suitable for pumpable concrete. Next is we should be aware of wide content of aggregate, grading of aggregate and uniformity in the quality of aggregate. So these things very important for pumping. Next is we should adjust the slump of our concrete 75 mm to the collapse range means above 75 slump is required for pumpable concrete. Now next thing is the diameter of the pipeline it must be at least 3 to 4 times the size of aggregate so which will facilitate a proper pumping. Now let us see what are the common problems in general in pumping of concrete. Most common problem is blockage which the cause we have seen two basic causes of the blockage we have seen. But during pumping what common problems are facing because of the blockage that is concrete fails to emerge at the end of pipeline. We are not getting the concrete at the end of the pipeline. The pump is mechanically sound concrete is not emerging it would mean that there is a blockage. So we can understand the somewhere concrete is blocked in the pipeline. Next is the pressure gauge is showing very high pressure or increase in the pressure and according to that the concrete is not pumped that is also one sort of problem. And we can say that there is a blockage somewhere in the pipeline. Now most blockages happen at the tapered section at the pump end. So we must handle that pump end properly and it must be kept with the proper shape. Now these are the reasons for blockages. First reason unsuitability of the concrete makes. So proper proportioning improper proportioning then improper workability means whatever workability is considered for the mix that is not assured during while working. Then the pipeline and joint deficiency then operators error this is one of the reason. Next high temperature for high temperature we are working then definitely there will be loss of the water from the mix and then blockage is may be the reason. Next is use of admixture. If accelerating type of admixtures are used with hygrids cement definitely that will set very fast and we will get the problem of blockage. Now continuous pumping is not done means intermittent pumping somewhere we have stopped and again the pumping started discontinuous pumping will lead to the blockage. And the pipeline which is not well cleaned after the previous operation and uncleaned worn out horses who says too many and too sharp bends use of worn out jaunts are also other reasons mechanical reasons for blockages. These are the references which I use for this session thank you.