Materials for Civil and Construction Engineers (4th Edition)
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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Chapter 7, Problem 7.1QP

The design engineer specifies a concrete strength of 5500 psi. Determine the required average compressive strength for:

  1. a. a new plant where s is unknown
  2. b. a plant where s = 500 psi for 22 test results
  3. c. a plant with extensive history of producing concrete with s = 400 psi
  4. d. a plant with extensive history of producing concrete with s = 600 psi

(a)

Expert Solution
Check Mark
To determine

The required average compressive strength for a new plant when standard deviation (s) is unknown.

Answer to Problem 7.1QP

The required average compressive strength for a new plant when s is unknown is 6,900psi_.

Explanation of Solution

Given information:

The concrete strength fc is 5,500 psi.

Calculation:

Determine the required average compressive strength for a new plant fcr.

fcr=fc+s

Here, s is the standard deviation.

Take standard deviation as 1,400 psi for compressive strength greather then 5,000 psi.

Substitute 5,500 psi  for fc and 1,400 psi for s.

fcr=5,500+1,400=6,900psi

Therefore, required average compressive strength for a new plant when standard deviation (s) is unknown is 6,900psi_.

(b)

Expert Solution
Check Mark
To determine

The required average compressive strength for a new plant when standard deviation (s) is 500 psi.

Answer to Problem 7.1QP

The required average compressive strength for a new plant when standard deviation (s) is 500 psi 6,240psi_.

Explanation of Solution

Given information:

The concrete strength fc is 5,500 psi.

Calculation:

Determine the modification factor for 22 number of test F22 using the interpolation.

F22=(F25F20)(T22T20T25T20)+F20

Here, F25 is the modification factor for the 25 number of tests, F20 is the modification factor for the 20 number of tests, T22, T20, and T25 are the number of tests.

Substitute 1.03 for F25, 1.08 for F20, 22 for T22, 20 for T20, and 25 for T25.

F22=(1.031.08)(2220)2520+1.08=1.06

Determine the modified standard deviation s.

s=s(F22)

Substitute 500 psi for s and 1.06 for F22.

s=500×1.06=530psi

Determine the required average compressive strength for a new plant fcr.

fcr=fc+1.34s

Here, s is the standard deviation.

Substitute 5,500 psi for fc and 530 for s.

fcr=5,500+1.34×530=6,210psi

Determine the required average compressive strength for a new plant fcr.

fcr=fc+2.33s500

Substitute 5,500 psi for fc and 530 for s.

fcr=5,500+2.33×530500=6,235psi

Take the maximum value from the calculated fcr values.

Use fcr value as 6,240 psi.

Therefore, the required average compressive strength for a new plant when standard deviation (s) is 500 psi is 6,240psi_.

(c)

Expert Solution
Check Mark
To determine

The required average compressive strength for a plant with extensive history of producing concrete with standard deviation (s) of 400 psi.

Answer to Problem 7.1QP

The required average compressive strength for a plant with extensive history of producing concrete with standard deviation (s) of 400 psi is 6,040psi_.

Explanation of Solution

Given information:

The concrete strength fc is 5,500 psi.

Calculation:

Determine the required average compressive strength for a new plant fcr.

fcr=fc+1.34s

Substitute 5,500 psi for fc and 400 for s.

fcr=5,500+1.34×400=6,036psi

Determine the required average compressive strength for a new plant fcr.

fcr=fc+2.33s500

Substitute 5,500 psi for fc and 400 for s.

fcr=5,500+2.33×400500=5,932psi

Take the maximum value from the calculated fcr values.

Use fcr value as 6,040 psi.

Therefore, the required average compressive strength for a plant with extensive history of producing concrete with standard deviation (s) of 400 psi is 6,040psi_.

(d)

Expert Solution
Check Mark
To determine

The required average compressive strength for a plant with extensive history of producing concrete with standard deviation (s) of 600 psi.

Answer to Problem 7.1QP

The required average compressive strength for a plant with extensive history of producing concrete with standard deviation (s) of 600 psi is 6,400psi_.

Explanation of Solution

Given information:

The concrete strength fc is 5,500 psi.

Calculation:

Determine the required average compressive strength for a new plant fcr.

fcr=fc+1.34s

Substitute 5,500 psi for fc and 600 for s.

fcr=5,500+1.34×600=6,304psi

Determine the required average compressive strength for a new plant fcr.

fcr=fc+2.33s500

Substitute 5,500 psi for fc and 600 for s.

fcr=5,500+2.33×600500=6,398psi

Take the maximum value from the calculated fcr values.

Use fcr value as 6,400 psi.

Therefore, the required average compressive strength for a plant with extensive history of producing concrete with standard deviation (s) of 600 psi is 6,400psi_.

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The design engineer specifies a concrete strength of 5500 psi. Determine the required average compressive strength for:a. a new plant where s is unknownb. a plant where s = 500 psi for 22 test resultsc. a plant with extensive history of producing concrete with s = 400 psid. a plant with extensive history of producing concrete with s = 600 psi
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The design engineer specifies a concrete strength of 5500 psi. Determine the required average compressive strength for a. a new plant where s is unknown b. a plant where s 7.1 500 psi for 22 test results Questions and Problems 309 c. a plant with extensive history of producing concrete with s = d. a plant with extensive history of producing concrete with s 400 psi 600 psi

Chapter 7 Solutions

Materials for Civil and Construction Engineers (4th Edition)

Ch. 7 - Prob. 7.11QPCh. 7 - Prob. 7.12QPCh. 7 - Students in the materials lab mixed concrete with...Ch. 7 - Students in the materials lab mixed concrete with...Ch. 7 - Why is it necessary to measure the air content of...Ch. 7 - What do we mean by curing concrete? What will...Ch. 7 - Discuss five different methods of concrete curing.Ch. 7 - Draw a graph showing the typical relation between...Ch. 7 - Why is extra water harmful to fresh concrete, but...Ch. 7 - Discuss the change in volume of concrete at early...Ch. 7 - Discuss the creep response of concrete structures....Ch. 7 - Prob. 7.22QPCh. 7 - On one graph, draw a sketch showing the typical...Ch. 7 - Using Figure 7.34, a. Determine the ultimate...Ch. 7 - Three concrete mixes with the same ingredients,...Ch. 7 - Three concrete mixes with the same ingredients,...Ch. 7 - Three 100 mm 200 mm concrete cylinders with water...Ch. 7 - Students in the materials class prepared three 4 ...Ch. 7 - Three 150 mm 300 mm concrete cylinders with water...Ch. 7 - Three 6 in. 12 in. concrete cylinders with water...Ch. 7 - A normal-weight concrete has an average...Ch. 7 - Discuss the significance of the compressive...Ch. 7 - What is the standard size of PCC specimens to be...Ch. 7 - Prob. 7.34QPCh. 7 - What is the purpose of performing the flexure test...Ch. 7 - What are the advantages of using a third-point...Ch. 7 - Consider a standard flexural strength specimen of...Ch. 7 - To evaluate the effect of a certain admixture on...Ch. 7 - To evaluate the effect of a certain admixture on...Ch. 7 - Prob. 7.40QPCh. 7 - Prob. 7.41QPCh. 7 - A normal-weight concrete has an average...Ch. 7 - Three batches of concrete were prepared using the...Ch. 7 - Three batches of concrete were prepared using the...Ch. 7 - Prob. 7.45QPCh. 7 - Prob. 7.46QPCh. 7 - Discuss two nondestructive tests to be performed...Ch. 7 - Discuss the concept of concrete maturity meters.Ch. 7 - Discuss four alternatives that increase the use...Ch. 7 - What is self-consolidating concrete? How are its...Ch. 7 - Prob. 7.51QPCh. 7 - Two 6 in. 12 in. concrete cylinders with randomly...Ch. 7 - Discuss the concept of high-performance concrete....Ch. 7 - Comparing PCC with mild steel, answer the...Ch. 7 - Prob. 7.55QP
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