EBK MATERIALS FOR CIVIL AND CONSTRUCTIO
4th Edition
ISBN: 8220102719569
Author: ZANIEWSKI
Publisher: PEARSON
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Textbook Question
Chapter 6, Problem 6.34QP
Referring to Table P6.34, Mix No. 1 was designed to produce a 25 mm (2 in.) slump without water reducer. Mixes Nos. 2–4 are trial mixes with water reducer. All mixes have the same amounts of aggregate and cement, different amounts of mixing water.
If the compressive strength at 28 days (fc′) follows the results shown in Figure 6.8, determine the following items:
- a. Water–cement ratio of each mix.
- b. fc′ of each mix
- c. The weight of mixing water required for a mix with water reducer having a 25 mm (2 in.) slump using the same amounts of aggregate and cement shown in the table.
- d. fc′ of the mix in Item c.
- e. Comment on the effect of adding water reducer to the mix and discuss how to make use of it to increase the compressive strength of concrete.
Assume that Figure 6.8 can be extrapolated. Use one system of units only as specified by the instructor.
* Assume all aggregates are in the SSD moisture state.
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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) Calculate the temperature of aggregates to produce fresh concrete having the sametemperature with the ambient temperature. Following data in Table 1 could be used:
Chapter 6 Solutions
EBK MATERIALS FOR CIVIL AND CONSTRUCTIO
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