Post on 28-Mar-2021
CEE3402 Reinforced Concrete StructuresSchool of Civil & Environmental EngineeringYonsei University, Seoul, Korea
Materials: Concrete and Steel
Kyoungsoo Park, Ph.D.
Spring, 2019
Kyoungsoo Park (k-park@yonsei.ac.kr)
Manufacture of Cement
CEE3402 | Spring, 2019 2
Kyoungsoo Park (k-park@yonsei.ac.kr)
Manufacture of Cement
CEE3402 | Spring, 2019 3
Limestonequarrying(crushing)
Other raw materials
Clay/shalequarrying(crushing)
Storage Storage
Grinding and blending
Grinding and blending
Storage and final blending
Finish grinding
Gypsum
Storage
Kyoungsoo Park (k-park@yonsei.ac.kr)
Cement Classification
Type I (Ordinary Portland Cement)
Type II (Moderate Heat Portland Cement)
Type III (High Early Strength Portland Cement) Smaller cement particles
Type IV (Low Heat Portland Cement)
Type V (Sulfate-Resisting Portland Cement)
CEE3402 | Spring, 2019 4
Kyoungsoo Park (k-park@yonsei.ac.kr)
Aggregate: Size Gradation
Economical Concrete
Uniform size versus Non-uniform size
Course Aggregate versus Fine Aggregate _______ mm Sieve (No. 4)
CEE3402 | Spring, 2019 5
Kyoungsoo Park (k-park@yonsei.ac.kr)
Concrete Mixing Design
Basic Consideration Economy
Reducing cement content Optimum ratio of coarse to fine aggregate
Workability Minimizing segregation and bleeding Slump test
Strength and Durability Minimum compressive strength at a given day Freezing & thawing (e.g. air content)
CEE3402 | Spring, 2019 6
Kyoungsoo Park (k-park@yonsei.ac.kr)
Water-Cement Ratio
CEE3402 | Spring, 2019 7
Kyoungsoo Park (k-park@yonsei.ac.kr)
Quality Control: Compressive strength
Specified design strength Compressive strength test
150 x 300 mm or 100 x 200 mm cylinder test Cylinder strength
Average compressive strength
CEE3402 | Spring, 2019 8
Freq
uenc
y
Compressive strength
Kyoungsoo Park (k-park@yonsei.ac.kr)
Concrete Mixing Design
Specified Mix (시방배합) Both coarse and fine aggregates are in the saturated-surface-dry
(SSD) condition All fine aggregate passes the No.4 (5 mm) sieve. All coarse aggregate is retained on the No.4 (5 mm) sieve.
Job Mix (현장배합) If aggregates do not satisfy the above requirements, the amount
of aggregates and mixing water should be modified
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굵은골재최대치수
(mm)
슬럼프범위(mm)
공기량범위(%)
물-결합재비
w/c(%)
잔골재율S/a(%)
단위질량(kg/㎥)
물W
시멘트C
잔골재S
굵은골재
G
혼화재료
혼화재¹ 혼화제²
Kyoungsoo Park (k-park@yonsei.ac.kr)
Special Placement
Shotcrete Spraying concrete from a nozzle Compacted on surfaces (e.g. vertical or steeply sloping
surfaces) Tunnel linings, stabilization of rock surface, surface supports No need for formwork
CEE3402 | Spring, 2019 10
Kyoungsoo Park (k-park@yonsei.ac.kr)
Special Placement
Tremie Pouring concrete under water Minimize entrapped air, and provide steady flow of concrete High slump
CEE3402 | Spring, 2019 11
Kyoungsoo Park (k-park@yonsei.ac.kr)
Consolidation
Elimination of void and entrapped air Corners of forms and around reinforcing steel Vibration: Internal and External Overvibration: bleeding, loss of entrained air
CEE3402 | Spring, 2019 12
Kyoungsoo Park (k-park@yonsei.ac.kr)
Curing
Objective As much hydration as possible
Strength & Durability Temperature & moisture during initial period Freezing of fresh concrete (4ºC or Lower): ____ of strength
Curing Maintenance of proper conditions for the initial period Protected from loss of moisture for _____ days / _____ days Springkling or covering with plastic film Low temperature: external heat High temperature: cooling concrete
CEE3402 | Spring, 2019 13
Kyoungsoo Park (k-park@yonsei.ac.kr)
Admixtures
Mineral Admixtures (Blended Cement) Supplementary cementitious material Fly ash, Silica fume, Blast furnace slag Heat of hydration, workability, strength development, durability Sustainable development: Reduce CO2 emission
Chemical Admixtures Water soluble compounds Air-entraining admixtures: Freezing and thawing resistance Accelerating admixture: Early strength development Set-retarding admixture: Workable for a long time Plasticizing admixtures: High-strength concrete Viscosity-modifier: Self-consolidating concrete
CEE3402 | Spring, 2019 14
Kyoungsoo Park (k-park@yonsei.ac.kr)
Stress-Strain Curves of Concrete
Normal Concrete Lightweight Concrete
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60
0.0030.0020 0.001
40
20
80
0.004
Com
pres
sive
stre
ngth
f c′ (
MPa
)
Strain, εc
60
0.0030.0020
Com
pres
sive
stre
ngth
f c′ (
MPa
)
0.001
40
20
80
0.004Strain, εc
Kyoungsoo Park (k-park@yonsei.ac.kr)
Stress-Strain Curves of Concrete
Effect of the Strain Rate
CEE3402 | Spring, 2019 16
Stre
ss
Strain
Kyoungsoo Park (k-park@yonsei.ac.kr)
Elastic Modulus
Definition of Elastic Modulus
CEE3402 | Spring, 2019 17
Stre
ss
Strain
fc′
Stre
ss
Strain
Kyoungsoo Park (k-park@yonsei.ac.kr)
Elastic Modulus
In Practice
wc = 1440 ~2560 kg/m3
Overestimate for compressive strength (42 ~ 84 MPa)
wc = 2300 kg/m3
Normal-density concrete: 21 ~ 84 MPa Lightweight concrete: 21 ~ 62 MPa
CEE3402 | Spring, 2019 18
𝐸 0.043𝑤 . 𝑓 ′
𝐸 3320 𝑓 6900𝑤
2300
.
𝐸 4700 𝑓 ′
Kyoungsoo Park (k-park@yonsei.ac.kr)
Tensile Strength Measurement
Splitting Test
CEE3402 | Spring, 2019 19
Plane of tensile failure
Concrete cylinder
Testing machine bed
Dis
tanc
e fr
om to
p of
spe
cim
en
Stress x πLD/2P
Kyoungsoo Park (k-park@yonsei.ac.kr)
Tensile Strength Measurement
Flexure Test (Modulus of Rupture)
CEE3402 | Spring, 2019 20
𝐿/3 𝐿/3 𝐿/3
𝐿
ℎ
𝑃2
𝑃2
Kyoungsoo Park (k-park@yonsei.ac.kr)
Approximate Range of Tensile Strength
Normal weight concrete Light weight Concrete
Direct tensile strength 0.25 to 0.58 𝑓 ′ 0.17 to 0.25 𝑓 ′
Split-cylinder strength 0.50 to 0.66 𝑓 ′ 0.33 to 0.50 𝑓 ′
Modulus of rupture 0.66 to 1.00 𝑓 ′ 0.50 to 0.66 𝑓 ′
CEE3402 | Spring, 2019 21
Kyoungsoo Park (k-park@yonsei.ac.kr)
Time-Dependent Deformation
Creep Increase of ____________ under __________________
Creep coefficient at time t (days), 𝐶
Ultimate creep coefficient, 𝐶
𝜀 : Instantaneous strain of concrete (or elastic strain) 𝜀 : Creep strain of concrete at time t (days) 𝜀 : Ultimate creep strain of concrete (Table 2.2)
𝐶.
. 𝐶
Effect of w/c ratio Effect of moist curing time & temperature
CEE3402 | Spring, 2019 22
Kyoungsoo Park (k-park@yonsei.ac.kr)
Creep of Concrete
CEE3402 | Spring, 2019 23
Cre
ep s
trai
n
Time (days)
Kyoungsoo Park (k-park@yonsei.ac.kr)
Time-Dependent Deformation
Shrinkage Decrease of _________ Cracking when each side is restrained Effect of w/c ratio Effect of aggregate content Self-desiccation
Water is consumed by hydration Low w/c ratio & no water during curing
Shrinkage strain after t days, εsh,t
CEE3402 | Spring, 2019 24
𝜀 ,𝑡
35 𝑡 𝜀 ,
εsh,u: Ultimate drying shrinkage strain (≈ 780x10-6)
Kyoungsoo Park (k-park@yonsei.ac.kr)
Shrinkage of Concrete
CEE3402 | Spring, 2019 25
Shrin
kage
str
ain
Time (days)
Kyoungsoo Park (k-park@yonsei.ac.kr)
Steel vs. Concrete
Compressive Strength 15 times higher than general concrete
Tensile Strength Over 100 times higher than general concrete
Thermal expansion coefficients Steel: 11.7 x 10-6
Concrete: 9.9 x 10-6
Corrosion resistance Concrete cover
Fire resistance High thermal conductivity Decrease of strength
CEE3402 | Spring, 2019 26
Kyoungsoo Park (k-park@yonsei.ac.kr)
Reinforcing Bars
Higher strength Reduce steel congestion
Less than fy = 550 MPa for most applications Minimum yield strength
Strain NOT exceed 0.0035
Types of deformed bars
CEE3402 | Spring, 2019 27
Kyoungsoo Park (k-park@yonsei.ac.kr)
Stress-Strain Relationships
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800
600
400
200
100
80
40
20
60
120
140
20010000
Grade 620
Grade 520
Grade 420
Grade 280
Stress, MPa
Strain, 0.001
ksi
800
600
400
200
100
80
40
20
60
120
140
201000
Grade 620
Grade 520
Grade 420
Grade 280
Stress, MPa
Strain, 0.001
ksi
3.5