UNIVERSITY OF CALIFORNIA AT BERKELEY CEE SPRING SEMESTER, 2003 Instructor: P.J. M. Monteiro Name:_____________________ CE 165 - EXAMINATION Answer in one or two lines: 1) Why do ASTM specification for Type IV cement limit the minimum content of C2S to 40 percent and the maximum C3A to 7 percent? 2) Why do ASTM Specifications for Type V cement limit the minimum C3A content to 5 percent? 3) Which compound is primarily responsible for rapid stiffening and setting of portland cement? 4) Why are clays and shales usually calcined (heat treated) to make more suitable for use as a pozzolan? 5) Portland cements are "hydraulic cements." What is the meaning of the term "hydraulic cement"?What type of cements would you recommend for concretes required in the following environments and why? 6. North pole 7. Oil wells 8. San Francisco harbor 9. Briefly define what is a pozzolan. 10. Give two examples of types of natural pozzolans. 11. Name the most common artificial pozzolan. 12. State two principal advantages of using pozzolans in concrete. 13. Name two important differences between silica fume and fly ash What type of admixture would you recommend to be used:14. to facilitate concreting in hot weather, and 15. for protecting hardened concrete against cycles of freezing and thawing? 16. To minimize the paste content, should you use an aggregate with a high or low dry-rodded unit weight? 17. List three important physical characteristics of aggregates. 18. Which properties of hardened concrete are greatly influenced by aggregates? Name three such properties. 19. Explain "bulking" of sand. 20. How does fly ash influence the properties of fresh concrete. 21. If you had a choice of three kinds of aggregate --a sandstone, a crushed basalt, and a quartzite, you may select the basalt. Give one possible characteristic or property of the sandstone and of the quartzite that made you decide not to select it for your concrete project.22. Give one property of fresh concrete and one of a hardened concrete that is significantly influenced by the shape and surface texture of the aggregate. 22. Presence of significant amounts of silt or clay in a concrete aggregate is deleterious. Explain why. 23. Give the two principal reasons for the use of air-entrainment in concrete. 24. What is the problem in using seawater for reinforced concrete? 25. When plasticizers are used, do the cement grains become hydrophobic or hydrophilic? Why? 26. List (a) two methods commonly used for measuring consistency, and (b) one method of measuring workability. 27. What is the difference between entrapped and entrained air? 27. How could you reduce the amount of bleeding of a concrete mix? Name at least two factors.28. Define "revibration". What effect does revibration of concrete have on compressive strength? 29. ACI Building Code for reinforced concrete permits a lower bond stress for a top reinforcing bar (max. 350 psi) than for a bottom bar (max. 500 psi). Explain why the top bar has a lower bond stress. 30. Explain what the is screeding performed during the placement of fresh concrete. 31. Explain why when added to Portland cement paste in very small amounts, calcium chloride acts as a retarder, but in large amounts behaves as an accelerator. 32. What happens to the setting time of a concrete, if too much air-entrained admixture is
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