Group members: Khamis Ahmed Khamis 199900588 Khalid Hazaá Mansour 200235841 Nasser Abdullah Alnaqbi...

Silica Fume influence on RC Beams Behavior

Group members:Khamis Ahmed Khamis 199900588Khalid Hazaá Mansour 200235841Nasser Abdullah Alnaqbi 200212673

Khaled Moussalli 200337587

United Arab Emirates UniversityCollege of Engineering

Department of Civil and Environmental EngineeringGraduation Project II

Second Semester 2007/2008

Advisor: Dr. Ahmed Bushlaibi

1Silica Fume influence on RC Beams Behavior

Department of Civil and Environmental Engineering

contents

Introduction. The split cylinder test. The permeability test. The bending test. The flexural test. Conclusion.

Silica Fume influence on RC Beams BehaviorDepartment of Civil and Environmental Engineering

Introduction

Using silica fume as an enhancer for the concrete beams, slabs, columns and any other concrete structure.

Concrete is very good material in compression however it is very week in tension so that is way we use reinforcement in it.

Cement grains (left), silica fume particles (right) at the same magnification. The ACI 234R-96 report estimates that for a 15 percent silica fume replacement of cement, there are

approximately 2,000,000 particles of silica fume for each grain of portland cement

Why Silica Fume ?

Change microstructure of the concrete

Physical aspect of silica fume :

Fills in the spaces between cement grains

Chemical contribution :

Cement releases calcium hydroxide. Silica has very high silicon dioxide.Calcium hydroxide will react with silicon dioxide to form

calcium silicate hydrate.

Why Silica Fume ?

Introduction

Concrete solidifies and hardens after mixing and placement due to a chemical process known as hydration. The water reacts with cement which bonds the other components together eventually creating a stone-like material.

Reinforcement is a good indication for failure because it gives us a warning.

Introduction

In GPI the concrete compression test was done. Was that enough ??!

Four more test were done. The split cylinder test. The permeability test. The bending test. The flexural test.

The split cylinder testThe permeability test.

The bending test.The flexural test.

Split Cylinder Test

Split cylinder test

This test, often referred to as the split-cylinder test, indirectly measures the tensile strength of concrete by compressing a cylinder through a line load applied along its length.

The testing machine

This test can be completed in a standard concrete compression testing machine, with only one special requirement the hinged bearing that loads the specimen.

The Experiment

Results

7 days

Results Silica %

0% 7.50% 10% 12.50%

261 261 327 356

258 250 300 362

250 260 315 352

Avg 256.33 257 314 356.67

The results above are in MPa

Results

14 days

Results Silica Fume %

0% 7.50% 10% 12.50%

270 351 342 357

270 333 347 376

285 343 342 357

Avg 281.67 342.33 343.67 363.33

28 days

Results Silica Fume %

0% 7.50% 10% 12.50%

370 380 450 480

370 400 435 475

340 400 445 480

Avg 360 393.33 443.33 478.33

Results

The split cylinder test.The permeability test.

Permeability

Permeability describes the ease by which any species (i.e. liquid or gas) can pass through concrete.

Objective :Effect of silica fume in permeability of concrete on different percentage (0%,7.5%,10%,12.5%)

Permeability

Most popular fluid is water Most popular gas is O2 & CO2

ConcreteSpecimen

Inflow

Flow path

OutflowWater permeatingthrough concrete

Permeability test

Shape: Cylinder

v=πr2h

R=15cm=0.15mr=7.5cm=0.075mh=2cm=0.02m

V =(π )*(0.075)2*(0.02)=0.00035m3

V for 16 cylinder = (16)*(0.00035) =0.0056m3

R=15cm

Calculation Water content for 16 cylinder=1.12Kg/m3

Cement content for 16 cylinder=3.3936kg

Fine Aggregate:

For 16 cylinder = 3.3432 Kg

Coarse Aggregate:

For 16 cylinder = 5.1072 Kg

Super plasticizer:

Sp=1.5 to 2 % of the total cement. SP= 1.65% * 3.3936 = 53 ml

Experiment

Curing

Oven3days

Water 25 days23

Transportation

To protect sample against air moisture24

Air permeability device

Line diagram for the oxygen permeability apparatus

The Permeability Cell

Permeability

Pressure head gradient

Cross Section(m2/sec)

Volume Flow Rate(m3/sec)

Permeability Coefficient(m/sec)

Driving ForcePressure head (m)

Flow Pathi.e. specimen thickness (m)

P(bar)

Volume

V(cc)t1

(sec)t2

(sec)t3

(sec)t_averag

(sec)Q

m3/secA

Km/sec

1.5 10 0.24 0.24 0.24 0.24 4.16667E-05 0.017671 0.02 1.5 3.14388E-05

2 10 0.11 0.11 0.11 0.11 9.09091E-05 0.017671 0.02 2 5.14454E-05

2.5 10 0.6 0.6 0.6 0.6 1.66667E-05 0.017671 0.02 2.5 7.54532E-06

3.01432E-05

P(bar)

VolumeV(cc)

t1(sec)

t2(sec)

t3(sec)

t_averag(sec)

Qm3/sec

Km/sec

1.5 10 6.8 6.82 6.77 6.796667 1.47131E-060.01767

1 0.02 1.5 1.11015E-06

2 10 2.8 2.82 2.8 2.806667 3.56295E-060.01767

1 0.02 2 2.01627E-06

2.5 10 1.6 1.65 1.63 1.626667 6.14754E-060.01767

1 0.02 2.5 2.78311E-06

1.96984E-06

P(bar)

VolumeV(cc)

t1(sec)

t2(sec)

t3(sec)

t_averag(sec)

Qm3/sec

Km/sec

1.5 10 11.5 11.5 11.52 11.50667 8.69061E-07 0.017671 0.02 1.5 6.55735E-07

2 10 5.21 5.23 5.25 5.23 1.91205E-06 0.017671 0.02 2 1.08202E-06

2.5 10 2.23 2.31 2.32 2.286667 4.37318E-06 0.017671 0.02 2.5 1.97982E-06

1.23919E-06

P(bar)

VolumeV(cc)

t1(sec)

t2(sec)

t3(sec)

t_averag(sec)

Qm3/sec

Km/sec

1.5 5 18.54 19.12 19.4 19.022.62881E-

07 0.017671 0.02 1.51.98347E-

2 5 8.82 8.68 8.79 8.7633335.70559E-

07 0.017671 0.02 2 3.2287E-07

2.5 5 5.41 5.4 5.41 5.4066679.24784E-

07 0.017671 0.02 2.54.18657E-

3.13291E-07

The silica fume will effect on the permeability as shown in the chart, when the quantity of silica fume increase the permeability will decrease.31

0 2 4 6 8 10 12 140.00E+00

5.00E-06

1.00E-05

1.50E-05

2.00E-05

2.50E-05

3.00E-05

3.50E-05

% Silica Fume

Design of RC Section Requires Determination of:

1. Concrete Dimensions

Beam width b

Depth of steel reinforcement d

Section height h = d + cover-to-center of steel

2. Area of steel reinforcement As

3. Ensure safety requirements (As) min ≤ As ≤ (As) max

Beam Design

Step 1: Assume Concrete Dimensions (Beam width & Section height) and Section Length

Beam width b = 100 mm

Section height h = 250 mm

Section Length L = 1.8 m

Beam Design

Step 2: Estimate Beam Height According to ACI Deflection Requirements

hmin = L/16 = 1800 / 16 = 113 mm

hb = 250 mm > 113 mm

Beam Design

Step 3: Assume bar size No. 10

For bar size No. 10, db = 9.5 mm

Beam Design

Step 4: Calculate depth of steel reinforcement (d)

Cover = concrete cover to steel center

cc = clear concrete cover (20 mm for beams)

ds = diameter of stirrups (bar size # 10)

db = diameter of steel bar (bar size # 10)

Hence, Cover = cc + ds + db/2 = 20 + 9.5 + 9.5/2 = 34 mm

d = h - cover = 250 - 34 = 216 mm

Beam Design

Step 5: Assume grade of a steel reinforcing bar & area of steel reinforcement As

Grade 420 (i.e. fy = 420 MPa) is the most commonly used steel

Use 2 bars No. 10 (As = 142 mm2)

Step 6: Compute steel ratio (ρ)

ρ = 142 / (100 * 216) = 0.00658

Beam Design

Step 7: Ensure safety requirements (ρ) min ≤ ρ ≤ (ρ) max

Beam Design

fyofGreater

600('85.0

)75.0( 1max fyfy

MPafcforfc 30''007.006.11

Step 7: Ensure safety requirements (ρ) min ≤ ρ ≤ (ρ) max

For fc' = 61.33 MPa 0.00466 ≤ ρ ≤ 0.03559

For fc' = 78.7 MPa 0.00528 ≤ ρ ≤ 0.04567

For fc' = 85.17 MPa 0.00549 ≤ ρ ≤ 0.04943

For fc' = 90 MPa 0.00565 ≤ ρ ≤ 0.05223

Beam Design

Experiment

Strain Gauges

Pouring the Concrete

The Smooth Concrete Surface

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,0000

Comparison of 0%, 7.5%, 10%, and 12.5% Silica Fume

0% Silica Fume7.5% Silica Fume10% Silica Fume12.5% Silica Fume

Strain

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,0000

Comparison of 0%, 7.5%, 10%, and 12.5% Silica Fume after 28 days

0% Silica Fume7.5% Silica Fume10% Silica Fume12.5% Silica Fume

Strain

One measure of the tensile strength. Measure of an unreinforced concrete. Loading beams with tow concentrated load.

What is Flexural Strength ?

Beam Details

Flexural Strength Experimentally

Flexural Strength Theoretically

fcu = 1.25 fc’

fc’ = 0.8 fcu

fr = 0.7 √ (0.8 fcu)

Theoretical Load

cm mm m

d1(cm) 15 150 0.15

d2(cm) 15 150 0.15

L(cm) 50 500 0.5

V(m3) 0.01125

For 7 beams 0.07875

Our Trial Mix Data

Water content for 7 beams = 200 x V

Cement content for 7 beams = 606 x V

Coarse Aggregate for 7 beams = 912 x VGrade 10_14 = 30%Grade 5_10 = 70%

Fine Aggregate for 7 beams = 597 x VDune sand = 20%Black sand = 80 %

Our Trial Mix Data

Experiment steps

WeightingPreparing

Mixing

Experiment steps

Mixing Prism Preparing

Concrete casting

After 2 days

Concrete Compression Machine

Consist of:

Two supporting rollers

Two load-applying rollers

Steel with circular cross-section

Diameter of 20 mm to 40 mm

At least 10 mm longer

Doing the Experiment

Result

ResultTime Vs F

10152025

303540

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Time ( Days )

12.50%

Result

ResultTime Vs F

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Time ( Days )

12.50%

Comparison

All the tests results were very encouraging.

Adding the silica fume to any concrete mixture will enhance the properties of the concrete far beyond its initial properties.

Increasing the amount of silica fume will result in enhancing the concrete properties.

Conclusion

The silica fume is a very promising industry in the future.

For the next semester it is recommended for one of the GPI groups to investigate the influence of fly ash on concrete and compare it with our results.

Conclusion

THANKS FOR

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