use of concrete Archives - OnlineEngineeringNotes
https://onlineengineeringnotes.com/tag/use-of-concrete/
A Complete Guide to future EngineersTue, 18 Oct 2022 15:30:26 +0000en-US
hourly
1 https://wordpress.org/?v=6.5.3Introduction to Concrete Technology and Constituents of Concrete
https://onlineengineeringnotes.com/2022/10/18/introduction-to-concrete-in-structure-and-constituents-of-concrete/
https://onlineengineeringnotes.com/2022/10/18/introduction-to-concrete-in-structure-and-constituents-of-concrete/#respondTue, 18 Oct 2022 13:45:33 +0000https://onlineengineeringnotes.com/?p=14331.1 Use of concrete in structure Concrete: Composite mixture of binder, aggregate, water and sometimes admixture. Commonly used building material. Merit: Ability to cast in any shape Economic Durable Fire and water resistant High strength Demerit: Low tensile strength Low toughness Low curing time Uses: Resistance to weather and fire resistant Strength increases with time ... Read more
Composite mixture of binder, aggregate, water and sometimes admixture.
Commonly used building material.
Merit:
Ability to cast in any shape
Economic
Durable
Fire and water resistant
High strength
Demerit:
Low tensile strength
Low toughness
Low curing time
Uses:
Resistance to weather and fire resistant
Strength increases with time
Economical and energy efficient
Durable
1.2 Constituent of concrete:
1. Coarse and Fine aggregate:
Chemically inactive material i.e. inert material.
Obtain from disintegration of strong rock. Example : gravel, pebble, sand etc.
Contributes 70 to 80 % of volume of hardened concrete.
Properties of good aggregate:
Must be clean, hard, strong, dense, durable, properly shaped, well graded.
Inertness and soundness.
High strength and toughness.
High bond strength.
Angular shape aggregate are good due to good interlocking.
2. Cement:
Chemically active ingredient of concrete which shows binding properties after reaction with water.
Manufactured by dry and wet process.
Components used for making cement are:
i. Limestone, clay, chalk-lime (60%)
ii. Silica (20%)
iii. Aluminium (10%)
Iv. Others: Iron oxide, carbon dioxide etc.
Bougie compound:
Bougie compound are formed during hydration of cement.
Compound
Formula
Symbol
% by mass in cement
1. Tricalcium silicate
3CaO.SiO2
C3S
20 – 50%
2. Dicalcium silicate
2CaO.SiO2
C2S
20 – 45%
3. Tri- calcium aluminate
3CaO.Al2O3
C3A
2 – 12%
4. Tetra calcium alumino ferrite
4Cao.Al2O3.Fe2O3
C4AF
6 – 12%
1. Tricalcium silicate: Responsible for initial setting and early strength.
2. Dicalcium silicate: Provide good ultimate strength.
3. Tricalcium aluminate: First compound to react with water.
4. Tetra calcium aluminate ferrite: Poor cementing value and less active.
Types of cement:
Ordinary Portland cement
Portland pozzolana cement
Rapid hardening cement
White cement
Colored cement
Acid resistant cement
Low heat cement
Quick setting cement
Test of cement:
Fineness
Setting time
Soundness
Specific gravity
Tensile strength
Compressive strength
3. Admixture:
A material other than basic ingredient like cement, aggregate and water which are used to alter the properties of concrete for specific purpose such as workability, w/c, setting time and strength can be changed.
Added in powder or liquid form.
Purpose:
1. To modify fresh properties:
Increasing the workability without changing water cement ratio.
(This process is also known as plasticizer.)
Retard or accerate the intial setting time.
Modify rate of bleeding.
2. To modify harden properties:
Reduce the heat of evolution.
Accelerate the rate of strength developed at early stage.
Increase durability.
Types of admixture:
1. Chemical admixture:
Material is form of powder or fluid that are added to concrete to give certain characteristics.
Less than 5% added at the time of mixing.
Accelerator: Increase rate of hydration.
Retarder: Slow down rate of hydration.
Entrapped air:
Air bubble are formed inside concrete unintentionally due to less compaction.
Entrained air:
Air bubble is added intentionally to concrete to change the properties of concrete.
2. Mineral admixture:
Very fine grain inorganic material which are added to concrete to improve properties of concrete.
Needs large amount of volume compare to chemical admixture.
Use:
Increase water tightness.
Increase early strength.
Increase workability.
Decrease heat evolution.
References:
Dayaratnam, P. Brick and reinforced brick structure.
Neville, A.M. Properties of Concrete. England: Pearson Education Limited.
Hendry, A.W., Sinha, B.P. & Davies, S.R. Design of Masonry Structure. London: E & FN Spon.