Note for CONCRETE TECHNOLOGY - CT by Mayank Jadaun

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Concrete Technology Prof. B. Bhattacharjee Department of Civil Engineering Indian Institute of Science, Delhi Lecture - 1 Cement Production and Composition Welcome to concrete technology, module 1 lecture 1. We shall be discussing about cement production and composition in this lecture. Of course, we start with, we will just introduce concrete as a material, because is a coition concrete technology. (Refer Slide Time: 00:49) (Refer Slide Time: 01:19)

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So, general outline of our discussion will be concrete material, components of concrete and also we will just mention concrete as a component. At the end, we will talk about cement, the production process and its composition. Now, what is concrete? Perhaps you would have seen concrete or also studied about it. Concrete is made up of components sachets, aggregation of stones, which we called as aggregate embedded in cement mortar that is cement-sand mortar, in his hardened state concrete is aggregation of stones or similar hard material embedded in what we call cement-sand mortar. The aggregates, aggregates in normal concrete forms this skeleton matrix; it is about 60 to 65 percent by volume and rest all is 25 percent is a paste; now paste means cement and water, that combines to paste. So, this aggregate when we talking of it is the large aggregation of stones, sand etcetera etcetera put together. 1 to 2 percent words are usually there in normal concrete. It is required that the aggregate shall be inert and strong, inert means should not be reacting with anything and it should be strong. It should strong, so that it can carry the load. So, that it can carry the loads, so that it can carry the concrete can which ten forces. (Refer Slide Time: 03:15) Ingredients of concrete, therefore if you look at the ordinary concrete or normal concrete it is made up by mixing inorganic material known as cement. I said cements and water, so this is cement is one other component, water together with cement forms what is called paste and the naturals sand or stone dust like something like this as we can see.

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Stone dust or naturals sand and you know, in addition to that will have course aggregate which quite often could be coarse stone or natural uncrushed stones themselves. So, there for concrete is generally normal concrete or very conventional concrete is made up of cement plus water plus water, this two makes paste, sand which are, which we called as fine aggregate, could be sand or crushed stone powder. Then stones which forms are course aggregates. So, that is generally the concrete normal concrete, generally the normal concrete. (Refer Slide Time: 04:45) But modern concretes if you look at it, it is not only this four components, but it has definitely two more components. So, modern engineered concrete has additional ingredients other than the four components just mention, right? These are chemical admixtures, these are chemical admixtures like they some of them are called accelerator, set retarders, water reducers etcetera. This ones are added to the concrete system during production, in order to improve the performance of concrete, either in frustrate or in hardened state. We will discuss about them later on in details. Mineral admixtures, this is the other kind of material which goes into the concrete, sometimes even in cement making and this are fly ash, silica fume, rice husk ash and other pozzolana or similar other material. So, as we can see modern concrete is not four component material, but six components

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material. So, a modern engineered concrete is actually six components material rather than four component material, rather then four component material, all right, okay? (Refer Slide Time: 06:27) Chemical admixture admixtures as I mention, therefore specific property performance enhancement. Specific property of performance an enhancement and mineral admixtures they do improve long term strength and durability performance. So, therefore these two admixtures are must in modern engineered concrete. Of course, manually produced concrete, non engineered concrete may not include this, but an engineered concrete definitely includes this two item as well. Using this admixtures it has become possible to obtained high strength materials, you know modern high strength and high performance concrete, right? You can design the concrete as you like, so this is what the concrete is, this is what the concrete is.