Materials for Civil and Construction Engineers (4th Edition)
4th Edition
ISBN: 9780134320533
Author: Michael S. Mamlouk, John P. Zaniewski
Publisher: PEARSON
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Textbook Question
Chapter 6, Problem 6.39QP
A materials engineer is working in a research project to evaluate the effect of one type of admixture on the compressive strength of concrete. She tested 10 mortar cubes made without admixture and 10 others with admixture after 28 days of curing. The compressive strengths of cubes without admixture were 25.1, 24.4, 25.8, 25.2, 23.9, 24.7, 24.3, 26.0, 23.8, and 24.6 MPa. The compressive strengths of cubes with admixture were 25.3, 26.8, 26.5, 24.5, 27.2, 24.8, 24.1, 25.9, 25.3, and 25.0 MPa. Using the statistical t-test, does this admixture show an increase in the compressive strength of the cement mortar at a level of significance of 0.05?
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A materials engineer is working in a research project to evaluate the effect of one type of admixture on the compressive strength of concrete. He tested eight mortar cubes made with admixture and eight others without admixture after 28 days of curing. The compressive strengths of cubes in psi with and without admixture are shown in Table P6.40.Using the statistical t-test, is there a significant difference between the meansof the compressive strengths of the two cement mortars at a level of signifi-cance of 0.10?
A materials engineer is working in a research project to evaluate the effect
of one type of admixture on the compressive strength of concrete. He tested
eight mortar cubes made with admixture and eight others without admixture
after 28 days of curing. The compressive strengths of cubes in MPa with and
without admixture are shown in Table P6.38.
Using the statistical t-test, is there a significant difference between the means
of the compressive strengths of the two cement mortars at a level of signifi-
cance of 0.10?
TABLE P6.38
Compressive Strength, MPa
Cube No.
With Admixture
Without Admixture
1
24.2
24.4
2
25.1
26.0
3
25.6
25.6
4
24.1
25.1
23.5
24.5
25.4
25.1
7
24.4
23.4
24.2
24.5
8.
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.
Chapter 6 Solutions
Materials for Civil and Construction Engineers (4th Edition)
Ch. 6 - What ingredients are used for the production of...Ch. 6 - What is the role of gypsum in the production of...Ch. 6 - What is a typical value for the fineness of...Ch. 6 - What are the primary chemical reactions during the...Ch. 6 - Define the C-S-H phase of cement paste.Ch. 6 - What are the four main chemical compounds in...Ch. 6 - Prob. 6.7QPCh. 6 - Define a. interlayer hydration space b. capillary...Ch. 6 - Prob. 6.9QPCh. 6 - The following laboratory tests are performed: a....
Ch. 6 - What is a false set of portland cement? State one...Ch. 6 - The watercement ratio is important because it...Ch. 6 - Discuss the effect of watercement ratio on the...Ch. 6 - Draw a graph to show the general relationship...Ch. 6 - Students in the materials class prepared three...Ch. 6 - Students in the materials class prepared three...Ch. 6 - Two batches of cement mortar with properties as...Ch. 6 - What are the five primary types and functions of...Ch. 6 - Why isnt pozzolan used with Type III cement?Ch. 6 - What type of cement would you use in each of the...Ch. 6 - In order to evaluate the suitability of nonpotable...Ch. 6 - Three standard mortar cubes were made using...Ch. 6 - Four standard mortar cubes were made using...Ch. 6 - Discuss the problem of disposal of waste water...Ch. 6 - State five types of admixtures and discuss their...Ch. 6 - Prob. 6.27QPCh. 6 - Under what condition is an air-entraining agent...Ch. 6 - If a water reducer is added to the concrete mix...Ch. 6 - Prob. 6.30QPCh. 6 - A concrete mix includes the following ingredients...Ch. 6 - The results of an experiment to evaluate the...Ch. 6 - The results of a laboratory experiment to evaluate...Ch. 6 - Referring to Table P6.34, Mix No. 1 was designed...Ch. 6 - Two batches of concrete cylinders were made with...Ch. 6 - Two batches of concrete cylinders were made with...Ch. 6 - What is the source of fly ash? Why is fly ash...Ch. 6 - A materials engineer is working in a research...Ch. 6 - A materials engineer is working in a research...
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- A concrete test cylinder is tested in compression after 7 days of moist curing. If the strength is 22.5 MPa, what do you predict for the projected 28-day strength knowing that the sample only gain 80% strength at 7 days?arrow_forwardComplete the tablearrow_forwardThe 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)arrow_forward
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