Chapter 7, Problem 7.30QP

Three 6 in. × 12 in. concrete cylinders with water to cement ratios of 0.4, 0.6, and 0.8, respectively. After curing for 28 days, the specimens were subjected to increments of compressive loads until failure. The load versus deformation results were as shown in Table P7.30.

Assuming that the gauge length is the whole specimen height, it is required to do the following:

1. a. The compressive stresses and strains for each specimen at each load increment.
2. b. Plot stresses versus strains for all specimens on one graph.
3. c. The ultimate strength for each specimen.
4. d. The modulus of elasticity as the secant modulus at 40% of the ultimate stress for each specimen.
5. e. The strain at failure for each specimen.
6. f. The toughness for each specimen.
7. g. Comment on the effect of increasing the water-cement ratio on the following:
   1. i. Ultimate strength
   2. ii. Modulus of elasticity
   3. iii. Ductility
   4. iv. Toughness. Curves may be approximated with a series of straight lines.

TABLE P7.30

	Specimen No.
	1	2	3
w/c Ratio	0.4	0.6	0.8
Deformation (in.)	Load (kips)
0	0	0	0
0.012	124	82	62
0.024	195 (failure)	110	79
0.036		102 (failure)	68
0.048			51 (failure)