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Modulus of Elasticity and Poisson Ratio of Concrete Benjie Cho and Mulugojam Alemu Undergraduate Civil Engineering Univ.. of Southern California

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Objective Find the Modulus of Elasticity of Concrete Find Poisson’s Ratio of Concrete

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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

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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.

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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.

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Procedure Set gauge factor to /-.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.

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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.

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Calculation procedures Young’s Modulus –E=(s 1 -s 2 )/( ) 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 – =(Lateral Strain)/(Longitudinal Strain)

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Example

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Cylinder #2

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Cylinder #3

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Cylinder #4

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Cylinder #5

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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=

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Conclusion Concrete performed to design specifications. –E= ksi – =.1 Xiao, Yan. Experimental Analysis of Engineering Materials. University of Southern California lecture notes 2002.

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