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UNIVERSITY OF CALIFORNIA AT BERKELEY DEPARTMENT OF CIVIL ENG.SPRING SEMESTER, 2008 Instructor : P.J. M. Monteiro

Name of the Student:_____________________

CE 241 - EXAMINATION

Justify all your answers

Question 1

I) A cement paste sample is analyzed in the laboratory and the following composition

was determined: 58 cm3of unhydrous cement, 33 cm

3of hydration products and 8%

of pores filled with water. Compute the hydration degree and the original water-to-cement ratio (14 points)

II) What raw material of Portland cement provides the .source of aluminum for the

formation of C3A? ( 5 points)

III) Give two advantages and two disadvantages of having cement with high C3A content.

(8 points)

IV) Explain how the interfacial transition zone is affect by thewall effect and the one

side growth? (4 points)

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Question 2

I) (a) Compute the elastic strain when a stress of 80 MPa is applied the rheological

model shown below. (b) Compute the total strain after 30 days. (15 points)

II)

During a compression test, the axial strain in the concrete cylinder is 600 10-3.Assuming a Poissons ratio equal to 0.2, compute the volumetric strain in the

cylinder. (6 points)III) Is there any difference in the concrete specimen if you perform the compression test

under constant stress rate or under strain rate? Please justify your answer. (4 points)IV) Does the splitting test creates a state of uniform tension in the whole specimen (4

points)

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Question 3

I) ) For a 4000-psi concrete, a contractor has an option of using the aggregate from Santa Rosa

with elastic modulus of 40 GPa or from Santa Monica with elastic modulus of 25 GPa. (10points)

a) Which concrete will have a higher compressive strength?

b)

Which concrete will have higher creep?c) Which concrete will have higher shrinkage?d) Which concrete will have higher thermal stresses?e) Would the answers be different if instead of 4000 psi concrete the job requires a 9000 psi

concrete?

II) Why is it necessary to have as little water as possible in concrete mixtures for the constructionof conventional concrete gravity dams? (6 points)

III) Normally laboratories do test concrete samples in torsion. Do you think that a torsion testwill give a good indication of the shear strength of the concrete? Justify your answer. (7 points)

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Question 4

I) Ettringite causes damage when formed during sulfate attack however it does not causecracking during the cement hydration. Explain his phenomenon. (6 points)

II) Explain why the presence of gypsum in concrete is a clear indication of sulfate attack. (8points)

III) Cracks were observed after a few weeks since placing the concrete. The contractor blamesthe aggregate because it could be reactive and lead to the deleterious alkali-aggregate reaction.

Write a short memo agreeing or disagreeing with the claim. What types of tests would yourecommend to perform in the damaged concrete if the case goes to court? (8 points)

IV).Give 3 recommendations to reduce the adiabatic temperature rise of concrete. (6 points)