Properties of Portland Cement Concrete Concrete Ingredients

Home , Portland cement

5% 10% Gravel 40% Sand 20% Water Cement Mortar Paste Air 25%

CIVL 3137 2 Concrete Strength

1. Aggregate

2. Cement/Aggregate Bond

3. Cement Paste

CIVL 3137 3 Water-Cement Ratio

0.2

CIVL 3137 4 Water-Cement Ratio

gallons of water w/c  gallons sack sacks of cement

1 sack of cement 1ft3 bulk 94 lb

1 gallon of water 8.34 lb

CIVL 3137 5 Water-Cement Ratio

mass of water w/c  dimensionless mass of cement

mass of water w/cm  mass of cement + SCMs

CIVL 3137 6 Water-Cement Ratio

TYPICAL RANGE

0.2

0.25 = Full Hydration

CIVL 3137 7 Water-Cement Ratio

Vibrated

Rodded

CIVL 3137 8 Water-Cement Ratio

Cement Water

0% Hydration

Hydration Products WaterAir

100% Hydration

CIVL 3137 9 Cement Paste Strength

Air Content of Paste - percent

CIVL 3137 10 Freeze-Thaw Durability

CIVL 3137 11 Freeze-Thaw Durability

CIVL 3137 12 Air Entrainment

CIVL 3137 13 Air Entrainment

(data from tests on mortar cubes)

CIVL 3137 14 Air Requirements

CIVL 3137 16 Air Content

Mortar Air Content

60% Assume 9% Mortar

Concrete Air Content 0.6  9% = 5.4% 40% Gravel 3/4″ NMAS

CIVL 3137 17 Air Content

Mortar Air Content

50% Assume 9% Mortar

Concrete Air Content 3″ 0.5  9% = 4.5% 50% Gravel NMAS

CIVL 3137 18 Air Requirements

8 7 6 ⅜"

5 ¾" 1½" 4 NMAS = 3" 3 2 Total Air Content (%) Total Optimum Air Content = 9% of Mortar Volume 1 0 40 50 60 70 80 Mortar Content (%)

CIVL 3137 19 Properties Affected by Air Content

durability consistency strength bleeding

CIVL 3137 20 Air Entrainment

CIVL 3137 21 Air Entrainment

CIVL 3137 22 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 23 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 24 Workability

workability (n.) the ease with which the concrete ingredients (gravel, sand, cement, water) can be mixed, transported, placed, consolidated, and finished with minimum loss of homogeneity.

CIVL 3137 25 Workability

refers to the stickiness of the concrete and how easily it can be placed and finished without inhomogeneity workability = consistency + cohesion

refers to the fluidity of the concrete and how easily it can be transported, placed, and consolidated without inhomogeneity

CIVL 3137 26 Inhomogeneity segregation (n.) the tendency for the gravel particles to separate from the rest of the ingredients. bleeding (n.) the tendency for the mixing water to separate from the rest of the ingredients.

CIVL 3137 27 Causes of Segregation

improper placement

too much mixing water

over-vibration

CIVL 3137 28 Causes of Bleeding

too little cement too much water over-vibration over-working

CIVL 3137 29 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 30 Harshness

CIVL 3137 31 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 32 Strength Gain Over Time

90 80 w/c = 0.3 70 60 w/c = 0.4 50 40 w/c = 0.5 w/c = 0.6 30 w/c = 0.7 20

Compressive Strength (MPa) (MPa) Strength Compressive 10 0 0 20 40 60 80 100 Age (days)

CIVL 3137 34 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 38 Tensile Strength

fftc 0.1 

CIVL 3137 39 Tensile Strength

 fftc 6.7  finpsic 

CIVL 3137 40 Beam Flexure Test

L 3

CIVL 3137 41 Modulus of Rupture

PL MOR  bd 2

CIVL 3137 42 Concrete Behavior

1 1

E E

CIVL 3137 43 Beam Flexure Test

PL MOR  bd 2 ft

CIVL 3137 44 Flexural Strength

finpsi MOR 8.4 fc c

finpsi fftc 6.7  c

MOR1.25 ftt or f 0.8 MOR

CIVL 3137 45 Flexural Strength

CIVL 3137 46 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 47 Stiffness and Strength

CIVL 3137 48 Stiffness and Strength Source: ACI Manual of Concrete Practice

1.5 E33wf c

E elastic modulus in lb in2 w unit weight in lb ft3 2 fc  compressive strength in lb in

CIVL 3137 49 Stiffness and Strength

E57,000f c

Typical test data

CIVL 3137 50 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 52 Durability

Sources of Deterioration

Alkali-Silica Freeze-Thaw Sulfate Reaction Cycles Attack aggregate type air content cement cement type w/c ratio type

CIVL 3137 53 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 54 Important Properties

workability harshness compressive strength tensile / flexural strength stiffness durability permeability shrinkage / creep

CIVL 3137 55 Shrinkage / Creep

Sources of Volume Change

Temperature Drying Creep Changes Shrinkage Strains

CIVL 3137 56 Coefficient of Thermal Expansion

Aggregate Coefficient Type (10-6 in/in/oF) Quartz 6.6 Sandstone 6.5 Gravel 6.0 Granite 5.3 Basalt 4.8 Limestone 3.8 Average 5.5

CIVL 3137 57 Example

How much strain would develop in a granitic concrete due to a 60°F temperature change?

6.0  1064 in/in/°F 60  F  3.6  10 in/in

CIVL 3137 58 Example

 3.6 104

CIVL 3137 59 Drying Shrinkage Coefficient

Tensile Shrinkage Strength Coefficient (psi) (in/in) 300 or less 0.0008 400 0.0006 500 0.00045 600 0.0003 700 or more 0.0002 Typical 0.0006

CIVL 3137 60 Example

How much will a typical 14-ft pavement slab shrink during curing if it is unrestrained?

6.0  104 in/in 14 ft 12 in/ft  0.10 in

CIVL 3137 61 Example

How much tensile stress will develop in the slab in the previous example if it is restrained?

E  3.6  1064 psi 6.0  10 in/in  2160 psi

CIVL 3137 62 CIVL 3137 63