Chapter 7, Problem 7.27QP

Three 100 mm × 200 mm concrete cylinders with water to cement ratios of 0.50, 0.55, and 0.60, respectively. After curing for 7 days, the specimens were subjected to increments of compressive loads. The load versus deformation results were as shown in Table P7.27.

Specimen No.	w/c Ratio	Load (kN)	Deformation (mm)	Stress (MPa)	Strain (m/m)	Secant Modulus (MPa)
1	0.50	0	0
		25	0.0007
		50	0.0014
		75	0.0021
		100	0.0029
2	0.55	0	0
		25	0.0008
		50	0.0016
		75	0.0025
		100	0.0036
3	0.60	0	0
		25	0.001
		50	0.0021
		75	0.0034
		100	0.0051

Assuming that the gauge length is the whole specimen height, determine the following:

1. a. The compressive stresses and strains for each specimen at each load increment.
2. b. Plot stresses versus strains for each specimen on one graph.
3. c. If the ultimate stress is 30, 25 and 20 MPa at 0.50, 0.55 and 0.60, respectively, determine modulus of elasticity as the secant modulus at 40% of the ultimate stress at each water–cement ratio.
4. d. Comment on the effect of increasing the water-cement ratio on the modulus of elasticity.