Modulus of Elasticity and Poisson Ratio of concrete

Modulus of Elasticity and Poisson Ratio of Concrete (with example)

Outline

  • Find the modulus of Elasticity of concrete
  • Find Poisson’s Ratio of Concrete

Introduction

–        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

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.
  •  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.
  • 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.

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 Young’s Modulus and Poisson’s ratio from the data.
  • Calculate the theoretical values the Young’s Modulus and Poisson’s ratio.

Calculation Procedures

  •    Young’s Modulus

–        E=(s1-s2)/(e2-.000005)

  •   s1=the stress corresponding to the longitudinal strain of 50 micro strain.
  •   s2=the stress corresponding to .4f ‘c.
  •   E2=the longitudinal strain corresponding to s2.
  •  Based on ASTM C 469
  •  Poisson’s Ratio

–        n=(Lateral Strain)/(Longitudinal Strain)

Conclusion

  •  All specimens performed under the theoretical values of E.

–        Average E= 2.60E6 psi

  •   Average Poisson Ratio= .119691

Power Point Presentation with an example has been embedded below for better understanding.

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