Hardend description of Concrete

1. “
”
Dissertation (2023)
HARDENED CONCRETE PROPERTIES
Presented By- Under the Guidance of -
 Singh Mr. MANISH
(HOD, CIVIL Department)
Department of Civil Engineering
Institute of Information Technology , Gorakhpur

2. Introduction
 Concrete is a composite material in which a binding material mixed in water on
solidification binds the inert particles of well graded fine and coarse aggregates.
 Cement and lime are generally used as binding materials, whereas sand cinder is used as
fine aggregates and crushed stones, gravel, broken bricks, clinkers are used as coarse
aggregates.

3. Strength
compressive strength 2000-8000 psi
tensile strength 200-800 psi
flexural strength
compression >> tension since concrete is notch sensitivite

4. Factors Affecting Strength
 Curing conditions, humidity
 Temperature
 w/c , (inversely related) Abram’s law
 air content, (inversely related), short and long term
 aggregate characteristics, roughness, grading, minerological.
 cement type, composition, fineness, type I vs. type III
 cement content (directly related)
 Strength porosity relationship
 mixing water

5. Strength and Curing
in air entire time
in air after 3 days
in air after 7 days
Strength
100%

6. Factors Affecting Concrete Strength

7. Resistance to freezing and thawing-Major
Factors
Air Entrainment
w/c, low water -cement ratio/ water content
volume stability, stiff aggregates with low coefficient of thermal
expansion

8. Durability
Resistance to freezing and thawing
Cracking
Internal Problems
Rebar Corrosion

9. Air Entrainment
 Resistance to freezing and thawing
 Water gains 9% in volume upon freezing
 nighttime freezing followed by daytime thawing,
 approximately 40 cycles per year, average. max of 200 cycles per year.
 fatigue loading of ice formation within pores
 Air Entraining Admixture (AEA) Must provide:
 Pore size
 Pore spacing
 Pore specific surface area

10. Internal Voids

11. Durability-Cracking
 path for harmful material to get into concrete
 sulfates- soils
 cause severe expansion, and deterioration
 chlorides -deicing salts
 initiate corrosion
 Excessive shrinkage

12. Durability-internal problems
 Alkali-silica reaction
 excessive sulfates

13. Rebar corrosion
NaCl
+ -

14. Mechanism of corrosion

15. Corrosion Protection
 Proper cover of at least 2”
 lower w/c
 denser concrete
 avoid using chlorides

16. Review
 Strength
 Durability
 Water Tightness
 water cement ratio
 Permeability
 Volume Stability
 shrinkage deformation with no load applied
 creep deformation under sustained loading

17. Load Induced Volume Changes


 E


c
.
concrete '
f
E 5
1
33

ft
cubic
/
lbs
,
concrete
of
weight
unit


psi
,
strength
e
compressiv
'
f c 

18. Load Induced Volume Changes

Creep deformation
Deformation
Time

19. Creep in Concrete

20. Consequences of creep
 Loss in pre-stress
 possibility of excessive deflection
 stressing of non load bearing members

21. Economy
 Cement Content
 50-60$/ton
 Aggregates
 5-6 $/ton
 minimum cement required at the minimum water cement ratio, with the maximum strength
and durability