Construction-of-Low-Cost-Houses/C2/Making-Plain-and-Reinforced-Concrete/English

Title of the Script: Making Plain and Reinforced Concrete

Authors: Dr. Narsingh Varma, Madhuri Ganapathi and Chitra Balaji

Key words: construction, cement, concrete, aggregate, stone, sand, concrete mixer, Segregation of concrete, measurement box, steel bars, spoken tutorial, video tutorial.

Visual Cue	Narration
Slide Number 1 Title slide	Welcome to the Spoken Tutorial on Making Plain and Reinforced Concrete.
Slide Number 2 Learning Objectives Slide Number 3 Learning Objectives	In this tutorial we will learn about, Materials required for making cement concrete Types and quality of aggregates and cement Tools used for making cement concrete Mix proportion for plain and reinforced concrete How to check the quality of fresh concrete
Slide Number 4 Prerequisites https://spoken-tutorial.org	To practise this tutorial, learners should be familiar with basic construction methods. For the prerequisite tutorials, please visit this website.
Slide Number 5 Materials required	We will begin with materials required for making cement concrete.
Images: 1,2, 5b, 13- combine into one picture.	The key ingredients for making plain cement concrete are: Cement Fine aggregate(that is sand) Coarse aggregate and water.
Image: 1a.	These ingredients are mixed together uniformly to make plain cement concrete.
Images: 1,1c,2, 5b, 13- combine to one picture.	Reinforced concrete It is a combination of plain cement concrete and steel bars as per design calculations.
Slide Number 6 Coarse and Fine Aggregate	Now we will discuss the types and quality of coarse and fine aggregates.
Slide Number 7 Coarse Aggregate	Coarse aggregate. Coarse aggregates are larger stones obtained from crushed rock and gravel. The range of coarse aggregate varies between 4.75 mm to 80 mm. The minimum size of coarse aggregate should be 4.75 mm.
Image: 1c-sieves.	Aggregates of different sizes are separated using Indian Standard (IS) sieves. IS Sieves of sizes 40 mm, 20 mm, 12.5 mm, 10 mm, 4.75 mm and others are used.
Images: 2 and 3	This is a good quality 20 mm nominal size aggregate. These stones are clean, hard and angular in shape. This is a good quality 10 mm nominal size aggregate. In the majority of concrete works, aggregate sizes of 20 mm or smaller are used. Both are good for making plain cement concrete and reinforced concrete.
Images: 4 and 4a.	This type of aggregate is elongated in shape. In this mixture, the ratio of coarse and fine aggregates are not known. It is a poor quality stone and not good for making concrete.
Images: 5, 5b	Fine aggregate. This is a 4.75 mm nominal size good quality natural sand. It is granular and is free from big size gravel, clay lumps and seeps.
Images: 6 and 6a	Fine Aggregate should pass through 4.75 mm sieve and retain on 0.075 mm sieve.
Image: 7 Images: 8 and 8a	This is a very fine aggregate or crushed sand. It contains more fine particles in the form of quarry dust. It is not good for concrete due to following reasons - Concrete made using stone dust as sand, will be more prone to shrinkage cracks. It needs more cement per cubic meter of concrete as compared to coarse sand.
Slide Number8 Cement	Now we will learn about different types of cement and its quality.
Image: 9	This is a Portland Pozzolana Cement (PPC) bag in good condition. The bag is neither hooked nor torn. It is good for construction.
Image: 10	Date of packing the bag is written on the side. Date of expiry of cement is 3 months from the date of packing. Cement older than 3 months should not be used without testing. Ordinary Portland cement(OPC) may also be used in place of PPC cement
Image: 11.	This is an ordinary Portland Cement (OPC) bag in good condition. Check for the ISI mark on the cement bags to ensure the quality of cement.
Image: 12	Torn cement bag is not good for use. Cement is lost through the cut portion of the cement bag. Cement gets partially hydrated when it is in contact with atmospheric moisture. The strength and durability of the cement is reduced.
Image: 13	This is loose cement without hardened lumps. When we put a hand inside a freshly opened cement bag, cement should not be warm. If cement is warm, it indicates that it is partially hydrated and not good for use.
Slide Number 9 Tools used in Making Cement Concrete	Now we will see the tools used in making cement concrete. wheelbarrow, measuring box and mixer.
Image: 14	This is a wheelbarrow. It is used to carry the freshly made concrete to the construction site.
Image: 15	This is an aggregate measurement box. Coarse and fine aggregates are measured using this box.
Images 16, 16b	This is a concrete Mixer. One cement bag along with required coarse and fine aggregates can be mixed in one batch. This type of mixers are either mechanically or electrically operated.
Image: 18 Images: 18a and 18b	Measurement of ingredients Cement is measured in the number of bags. Aggregates both fine and coarse are measured using measuring boxes.
Image: 19	Measuring boxes are to be filled up to box height and not above it.
Image: 19b	For PCC works, cement concrete mix ratios are as shown. CC 1:3:6 for a footing bed. CC 1:2:4 for flooring at plinth and plinth protection.
Slide Number 10 Plain Cement Concrete	Proportioning and measuring of ingredients for CC 1:3:6 plain cement concrete.
Image: 20 Image: 21 Image: 22 Image: 23	Cement: one(1) bag Fine aggregates : 3 boxes of sand. Coarse aggregates: 6 boxes of stone. Out of 6 the boxes, 3 boxes of 20 mm and 3 boxes of 10 mm, nominal sizes are used. 20 liters of water is added to make a homogeneous concrete. Add more water if concrete on visual inspection looks dry and non-homogeneous. Excess water should not be added as it reduces the strength of concrete.
Slide Number 11 Plain Cement Concrete	Proportioning and measuring of ingredients for CC 1:2:4 plain cement concrete.
Image: 24 Image: 25 Image: 26 Image: 27	Cement: 1 bag Fine aggregate : 2 boxes of sand. Coarse aggregate : 4 boxes of stone. Out of the 4 boxes, 2 boxes 20 mm and 2 boxes 10 mm, nominal sizes are used. Initially 15 liters of water is added to make a homogeneous concrete. More water may be added as required.
Slide Number 12 Reinforced Concrete	Concrete grade and proportioning of reinforced concrete.
Image: 28 Image: 29 Image: 30	M25 grade concrete for RCC work which is equivalent to CC 1:1:2 has to be used. That is, 1 part of cement, 1 part of fine sand and 2 parts of coarse aggregate. 20 mm and 10 mm nominal size coarse aggregates in equal ratio have to be used.
Slide Number 13 Mixing of Concrete	Mixing of concrete Now we will see the steps to be followed in mixing concrete.
Images: 31a , 31b Drum.mp4	First coarse aggregates are added to the mixer followed by cement and sand. Mix the materials in the dry state in the mixing machine for 2 minutes. Then add water to the drum. Minimum 3 minutes of mixing is required after putting all ingredients in the drum. Add more water while mixing if concrete on visual inspection looks dry.
Slide Number 14 Quality of Concrete	Now we will see how to check the quality of freshly made concrete.
Image: 32 Image: 33 Image: 34 Image: 34b Image: 35	Cement Concrete must be correctly proportioned and mixed uniformly. Concrete must be homogeneous after mixing. The formed concrete must be without bleeding or segregation. Segregation occurs when aggregates and cement in the concrete mix are separated. Bleeding occurs when water separates and rises above the concrete mix. Segregation and bleeding reduces concrete strength and durability.
Slide Number 15 Field Test of Concrete	Field test of concrete This test is used to check the cohesiveness of concrete produced at the site.
Images: Pic1 pic2 pic3 Image: Pic 4	Take a handful of freshly prepared concrete from the concrete mixer. Make a ball of concrete on your palm and hold it for 1 minute. If the ball does not collapse then the concrete is densely packed. This ensures strength and durability of concrete.
Slump Test	Slump cone test Slump cone test is the most simple workability test for concrete. Slump test is carried out for every batch of concrete. This is to check the uniform quality of concrete during construction.
Slump Test Images :1 to 9	Procedure of slump test. Clean the mould (that is slump cone) internally and apply shuttering oil. Place the mould on a plane plate with a larger diameter down. Fill the mould with sample concrete in 4 equal layers. Tamp layers with 25 strokes each using a tamping rod. Lift the mould upward gently and remove. Slump is the difference in height of the mould and height of the sample in mm. Complete the testing within 2 minutes of drawing the sample. A collapse slump generally indicates that the concrete mix is too wet. A zero slump indicates that the concrete is stiff and less workable.
Slide Number 16 Slump Requirement	For plain cement concrete, hand placed pavements and lightly reinforced sections, slump required is 25 mm to 75 mm. For heavily reinforced sections, slump required is 50 mm to 100 mm. Slump values for different concrete works are provided in, IS: 456 section 7.1.
Slide Number 17 Reference IS Codes	These are the reference IS codes. IS:456-2000 IS 383-2016 IS:269-2015 IS 1199-1959 IS:1489 (Part 1) Publisher of the reference IS codes : Bureau of Indian Standards, New Delhi.
Only Narration	With this we come to the end of this tutorial. Let us summarize.
Slide Number 18 Summary Slide Number 19 Summary	In this tutorial we have learnt about, Materials required for making cement concrete Types and quality of aggregates and cement Tools used for making cement concrete Mix proportion for plain and reinforced concrete How to check the quality of fresh concrete.
Slide Number 20 About Spoken Tutorial project	The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.
Slide Number 21 Forum for specific questions Do you have questions in THIS Spoken Tutorial? Please visit this site. [1] https://forums.spoken-tutorial.org Choose the minute and second where you have the question Explain your question briefly The Spoken Tutorial project will ensure an answer You will have to register to ask questions	Please post your timed queries in this forum.
Slide Number 22 Acknowledgements	The Spoken Tutorial Project was established by the Ministry of Education, Government of India.
Slide Number 23 Thank you	This tutorial is contributed by Dr. Narsingh Varma, Chitra Devi, Arthi Vardarajan and Madhuri Ganapathi from IIT Bombay Thank you for joining.

Contributors and Content Editors

Chitradevi