CE 421
Concrete Technology
Dr. Moonis Zaheer
Associate Professor, CED, AMU Aligarh
Course objectives
• To understand the properties of concrete ingredients i.e. cement, sand, coarse aggregates, water by studying and conducting different tests.
• To learn mix design procedure as per standard codes.
• To understand the factors affecting the properties of fresh and hardened concrete and new forms of concrete.
• To learn the application of admixtures in order to improve the properties of concrete.
• Infer the test results as per relevant IS provisions.
Course outcomes
Upon successful completion of this course, it is expected that students will be able to:
1. Know the materials and methods used to make concrete, including their sources, production and properties.
2. Explain the properties of fresh and hardened concrete.
3. Design normal concrete mixes and apply statistical quality control techniques to concrete quality.
4. Identify, describe and chose suitable form of concrete for a particular use at site.
Course syllabus
Unit 1:
Constituent materials of Concrete; Types, Properties and Tests as per Code, Concrete;
Production, Properties, tests and Quality Control, Introduction to Non-destructive Tests.
Unit 2:
Concrete Mix Design; Concepts, Methods , Sample problems using IS code method Characteristic and Target strengths, Sampling and acceptance criteria Equipments and methods for mixing, compaction , curing.
Unit 3:
Admixtures and construction chemicals; Types, method of mixing, Effect on different properties of concrete, Behaviour of Concrete in Extreme Climate: Permeability &
Durability, Effect of Temperature, Saline Environment, Sulphate & Acid Attack, Corrosion and Fire Resistance.
Unit 4:
Special forms of Concrete: Ferrocement, Fiber Reinforced Concrete, Polymer Concrete, Light Weight Concrete, High Density Concrete etc., Guniting or shotcreting.
Text Books and/or Reference Materials
1. Neville, A.M., “Properties of Concrete”, Longman, India
2. Neville, A.M. and & Brooks J.J. “Concrete Technology”, Longman, India
3. Shetty, M.S., “Concrete Technology”, SCC Ltd., New Delhi
4. I.S: 456-2000- Code of Practice for Plain and Reinforced Concrete 5. S.P.:16- Design aids for Reinforced Concrete to IS:456-2000
6. S.P.:23- Handbook on Concrete Mixes Additional Learning Source
• Web links to concrete technology, Nptel etc.
Lecture 1
Composition of concrete
Aggregate Requirements
• Aggregates should consist of particles with adequate strength against compression, impact, and abrasion.
• Aggregate particles should have resistance against aggressive exposure conditions such as highly fluctuating temperature and humidity.
• Aggregates should not contain deleterious materials such as chloride, sulfate, etc. that will cause deterioration of concrete.
• The fine aggregate must not have more than 45% retained between two consecutive standard sieves.
• The fineness modulus (FM) of fine aggregate must not be less than 2.3 nor more than 3.1.
Aggregate Requirements (cont.)
• Aggregates that do not have deficiency or excess of any size and give smooth grading curve will produce the most satisfactory results.
• The aggregate particle size is determined by using wire-mesh sieves openings.
• 6 standard sieves ranging from 150 micron to 4.75 mm for fine aggregates.
• 5 standard sieves ranging from 4.75 mm to 80 mm for coarse aggregates.
• Proper selection of various aggregate sizes will be very effective in reducing the total volume of voids.
• The cement paste requirement is related to the void content of the combined aggregates.
• There are different standards and specifications which specify grading limits for both fine and coarse aggregates.
• There are several reasons for specifying grading limits and maximum aggregate size, they affect relative:
Aggregate Requirements (cont.)
Gap-graded Aggregates
• When certain particle sizes are intentionally omitted-Gap graded aggregates.
• Ex., for an aggregate of 20 mm maximum size, the 4.75 mm to 10 mm particles can be omitted without making the concrete harsh subject to segregation.
• Gap-graded mixes are used in architectural concrete to obtain uniform textures in exposed aggregate finishes.
Particle shape and surface texture
• The shape and surface texture affect the properties of fresh concrete more than the properties of hardened concrete.
• Rough-texture, and angular particles require more water to produce workable concrete than do smooth, rounded and compact particles.
• Bond between cement paste and a given aggregate generally increases when the particles surfaces change from smooth and rounded to rough and angular.
• Aggregate should be free of flat or elongated particles. Because they require more water and thus may affect the strength of concrete.
Cement
• Crystalline compound of calcium silicates and other calcium compounds having
hydraulic properties.
• Considered hydraulic because of their ability to set and harden under water through the hydration of the cement’s chemical
compounds.
• Chemical reaction-Hydration.
• Paste coats all the aggregates together.
• Hardens and forms a solid mass.
Water
• Good water is essential for quality concrete.
• Should be good enough to drink -free of trash, organic matter and excessive chemicals and/or minerals.
• The strength and other properties of concrete are highly dependent on the amount of water and the water-cement ratio.
• Needed for two purposes:
Chemical reaction with cement
Workability
• Only 1/3 of the water is needed for chemical reaction.
• Extra water remains in pores and holes-Results in porosity.
• Bad for permeability, strength, durability.
• Sea water not to be used for prestressed concrete or for reinforced concrete.
• If unavoidable, it could be used for plain concrete.
Admixtures
• Mineral
Pozzolans
(fly ash, silica fume, shale,
calcined clay or metakaolin)
Slags
• Chemical
Set retarders
Set accelerators
Water reducing
Air entraining
