Modulus of Elasticity and Poisson Ratio of Concrete

1
Modulus of Elasticity and Poisson Ratio of
Concrete

• Benjie Cho and Mulugojam Alemu
• Undergraduate Civil Engineering
• Univ.. of Southern California

2
Objective

• Find the Modulus of Elasticity of Concrete
• Find Poissons Ratio of Concrete

3
Introduction

• Compressive Strength of Concrete
• Standardardized test of concrete
• American Society for Testing and Materials (ASTM)
• Specifications include
• Correct mix
• Properly affixing strain gauges
• Properly capping the cylinder with sulfur

4
Procedure

• Select (5) 4in diameter by 12in length concrete
  with 28-day age with 4 ksi design strength.
• Cap all the bearing surfaces with sulfur to make
  the end flat.
• Mark area where strain gauges will be attached.
• Clean area with chemical cleaners and sand paper.

5
Procedure

• Affix strain gauges on their designated area, one
  vertical and one horizontal, using glue.
• Attach wire to strain gauges by soldering.
• Test voltage of the strain gauges.
• Place and center samples on the Satec Universal
  Testing Machine.
• Connect the wires to the P3500 strain indicator,
  which in turn is connected to a computer for
  recording.

6
Procedure

• Set gauge factor to 2.055 /- .5 and zero the
  strain readings.
• Begin loading the specimens and record values of
  strain for given loads.
• Continue testing until failure of the specimen.

7
Organizing the data

• Compute the stress by dividing the load by the
  cross-sectional area.
• Graph the strength against the vertical and
  horizontal strains of each specimen.
• Find values for the Youngs Modulus and Poissons
  ratio from the data.
• Calculate the theoretical values the Youngs
  Modulus and Poissons ratio.

8
Calculation procedures

• Youngs Modulus
• E(s1-s2)/(e2-.000005)
• s1The stress corresponding to the longitudinal
  strain of 50 micro strain.
• s2The stress corresponding to .4f c.
• E2The longitudinal strain corresponding to s2.
• Based on ASTM C 469
• Poissons Ratio
• n(Lateral Strain)/(Longitudinal Strain)

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Example
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Cylinder 2
11
Cylinder 3
12
Cylinder 4
13
Cylinder 5
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Selected Values of Stress and Strain
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Selected Values of Stress and Strain
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Data
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Conclusion

• All specimens performed under the theorectical
  values of E.
• Average E 2.60E6 psi
• Average Poisson Ratio .119691

18
Conclusion

• Concrete performed to design specifications.
• E 1.5 - 5 ksi
• n .1
• Xiao, Yan. Experimental Analysis of Engineering
  Materials. University of Southern California
  lecture notes 2002.