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
- 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
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=(s_{1}-s_{2})/(e_{2}-.000005)
- s_{1}=the stress corresponding to the longitudinal strain of 50 micro strain.
- s_{2}=the stress corresponding to .4f ‘c.
- E_{2}=the longitudinal strain corresponding to s_{2}.
- 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.