6.38 What is the source of fly ash? Why is fly ash sometimes added to concrete? What are the different classes of fly ash?
6.38 What is the source of fly ash? Why is fly ash sometimes added to concrete? What are the different classes of fly ash?
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
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Answer only 6.38
![6.38 What is the source of fly ash? Why is fly ash sometimes added to concrete?
What are the different classes of fly ash?
6.39
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 compres-
sive 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?](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F93c89597-7ce2-4451-bd61-6716aa1c2201%2F749b185e-25bc-4bd2-ae8b-901e940ff4d3%2Fxpmnh04_processed.jpeg&w=3840&q=75)
Transcribed Image Text:6.38 What is the source of fly ash? Why is fly ash sometimes added to concrete?
What are the different classes of fly ash?
6.39
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 compres-
sive 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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