Two batches of concrete cylinders were made with and without a calcium chloride (CaCl2) accelerator admixture. Six cylinders were made of each batch and submerged in water for different times before testing for compressive strength and the results are shown in Table P6.34. It is required to do the following: a. Using an Excel sheet, plot the relationship between curing time and compressive strength of the two mixes on the same graph. Label all axes and curves. b. Comment on the effect of the accelerator on the compressive strength of PCC at early and late ages. TABLE P6.34 Cylinder no. 1 2 3 4 5 6 Water submergence (days) Compressive strength of plain concrete (MPa) Compressive strength of concrete with accelerator (MPa) 1 3 7 14 21 28 0.8 7.8 15.8 21.1 24.5 26.8 6.2 14.8 20.1 24.0 25.9 26.8

Two batches of concrete cylinders were made with and without a calcium chloride (CaCl2) accelerator admixture. Six cylinders were made of each batch and submerged in water for different times before testing for compressive strength and the results are shown in Table P6.34. It is required to do the following: a. Using an Excel sheet, plot the relationship between curing time and compressive strength of the two mixes on the same graph. Label all axes and curves. b. Comment on the effect of the accelerator on the compressive strength of PCC at early and late ages. TABLE P6.34 Cylinder no. 1 2 3 4 5 6 Water submergence (days) Compressive strength of plain concrete (MPa) Compressive strength of concrete with accelerator (MPa) 1 3 7 14 21 28 0.8 7.8 15.8 21.1 24.5 26.8 6.2 14.8 20.1 24.0 25.9 26.8

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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Two batches of concrete cylinders were made with and without a calciumchloride (CaCl2) accelerator admixture. Five cylinders were made of eachbatch and submerged in water for different times before testing for compres-sive strength and the results are shown in Table P6.36.It is required to do the following:a. Using an Excel sheet, plot the relationship between curing time andcompressive strength of the two mixes on the same graph. Label all axesand curves.b. Comment on the effect of the accelerator on the compressive strength ofPCC at early and late ages.
Two batches of concrete cylinders were made with and without a calciumchloride (CaCl2) accelerator admixture. Six cylinders were made of each batch andsubmerged in water for different times before testing for compressive strengthand the results are shown in Table P6.35.It is required to do the following:a. Using an Excel sheet, plot the relationship between curing time andcompressive strength of the two mixes on the same graph. Label all axesand curves.b. Comment on the effect of the accelerator on the compressive strength ofPCC at early and late ages.
2. In a ready-mix concrete plant, cylindrical samples are prepared and tested periodically to detect any mix problem and to ensure that the compressive strength is higher than the lower specification limit. The minimum target value was set at 5,000 psi. The following compressive strength data were collected. Sample No. 1 2 3 4 5 6 7 8 9 10 Compressive strength (psi) 5595 5139 6359 5192 5188 5241 5964 5875 6155 5115 Sample No. 11 12 13 14 15 16 17 18 19 20 Compressive strength (psi) 6695 5449 5278 6697 5195 6021 5320 5657 6595 5235 a. Calculate the mean, standard deviation, and the coefficient of variation of the data b. Using a spreadsheet program, create a control chart for these data showing the target value and the lower specification limit. Is the plant production meeting the specification requirement? If not, comment on possible reasons. Comment on the data scatter.
A concrete mix includes the following ingredients per cubic meter: a. Cement = 400 kg b. Water = 176 kg c. No admixture Table P6.30 shows possible changes that can be made to the mix ingredi- ents. Indicate in the appropriate boxes in the table what will happen in each case for the workability and the ultimate compressive strength as increase, decrease, or approximately the same.
A concrete mix includes the following ingredients per cubic meter: Cement%3D400 kg Water=184 kg No admixture Table below shows possible alternatives mix ingredients. Indicate in the appropriate boxes in the table what will happen in each case for the workability and the ultimate compressive strength as increase, decrease or approximately the same. What will happen? Cement Water Admixture (kg) (kg) Ultimate compressive Workability strength 400 225 None 449 184 None Water 400 184 Reducer Water 400 128 Reducer 400 184 Super Plasticizer 400 184 Air Entrainer 400 184 Accelerator DFocus
150 mm * 300 mm concrete cylinders were made of the same batch and separated at random to six equal groups. The six groups of cylinders were submerged in water for different times before testing for compressive strength and the results are shown in Table .It is required to do the following:a. Determine the compressive strength at different curing times.b. Using an Excel sheet, plot the relationship between curing time and compressive strength. Label all axes and curves.c. Comment on the effect of curing time on the compressive strength.d. What is the approximate ratio between the compressive strengths at 7 days and 28 days?e. What is the approximate ratio between the compressive strengths at 28 days and 180 days?
6.31 The results of a laboratory experiment to evaluate the effects of a plasticizer are shown below. a. Calculate the water/cement in each of the three cases. b. Using water reducer, how can we increase the compressive strength of con- crete without changing workability? Refer to the appropriate case in the table. 244 Chapter 6 Portland Cement, Mixing Water, and Admixtures With Water Reducer Without Water Reducer Case 1 Case 2 Case 3 Cement Content, kg/m 850 850 850 765 Water Content, kg/m Slump, mm Compressive Strength, MPa 465 465 370 419 50 100 50 50 37.8 38.0 46 37.9 c. Using water reducer, how can we improve workability without channging the compressive strength? Refer to the appropriate case in the table. d. Using water reducer, how can we reduce cost without changing workability or strength? (Assume that the cost of the small amount of water reducer added is less than the cost of cement.) Refer to the appropriate case in the table. Summarize all possible effects of water…
The results of a laboratory experiment to evaluate the effects of a plasticizer are shown.a. Calculate the water/cement in each of the three cases. b. Choose an appropriate case that - by using water reducer, how can we increase the compressive strength of concrete without changing workability? (Refer to the appropriate case in the table) c. Choose an appropriate case that - by using a water reducer, how can we improve workability without changingthe compressive strength? (Refer to the appropriate case in the table)d. Choose an appropriate case that - by using water reducer, how can we reduce cost without changing workability or strength? (Refer to the appropriate case in the table)
6.33 The results of a laboratory experiment to evaluate the effects of a plasticizer are shown below. d. Using water reducer, how can we reduce cost without changing workability or strength? (Assume that the cost of the small amount of water reducer added is less than the cost of cement.) Refer to the appropriate case in the table. e. Summarize all possible effects of water reducers on concrete.
Compare and discuss the microstructural characteristics of the materials. MERICA FIGURE A.15 Concrete microstructure using optical microscope. FIGURE A.16 Viewing concrete specimen with an optical microscope.
a) Calculate the temperature of aggregates to produce fresh concrete having the sametemperature with the ambient temperature. Following data in Table 1 could be used:
Three 150 mm * 300 mm 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 .Assuming that the gauge length is the whole specimen height, it is required to do the following:a. The compressive stresses and strains for each specimen at each load increment.b. Plot stresses versus strains for all specimens on one graph.c. The ultimate strength for each specimen.d. The modulus of elasticity as the secant modulus at 40% of the ultimate stress for each specimen. e. The strain at failure for each specimen.f. The toughness for each specimen. g. Comment on the effect of increasing the water–cement ratio on the following:i. Ultimate strengthii. Modulus of elasticityiii. Ductilityiv. Toughness. Curves may be approximated with a series of straight lines.