Required Calculations (for 7, 14, 21, and 28 day tests)
– Axial stress (at each increment)
– Axial strain over gage length (at each increment)
–
Experimental E from stress-strain curve as described above
– Design E as specified by ACI
– Experimental K from force-displacement curve as described above
– Theoretical K (use experimental E)
Required Plots
–
f’c for each day vs. time in days (include f’c from each lab section)
– Stress vs. Strain for 7, 14, 21, and 28 plotted together on one graph
Required Discussion
Discuss the mode of failure of each cylinder for 7, 14, 21, and 28 day tests. Did it fail as
expected, or did you see any deviations? Explain what you observe using the following as
guidelines:
– Mix procedure. Did your mix go well, or were there inconsistencies? If the latter, explain what
went wrong and how this ties into the observed failure mode.
– Adherence to ASTM procedure during the pour. Were the cylinders properly prepared, or did
you notice anything that may have contributed to an uneven cylinder (think in terms of the
layering, tamping, and tapping process)
Compare your results with the 7 and 28 day strengths from concrete pours used in previous experiments
in the SDSU shaking table lab. Are your results close, or do you have a weaker or stronger mix? Explain.
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