UNIVERSITY OF CALIFORNIA AT BERKELEY CEE SPRING SEMESTER, 2004 Instructor: P.J. M. Monteiro Name:_____________________ CE 165 - EXAMINATION Please justify your answer in all the questions Question 1(17 points) I) Give the approximate dimensions for the following: (8 points) Cement particle: Silica fume: Sand grain Air-entrained air voids: II) The architecture wants to build a concrete structure that has a ligther shades of gray. Which cement should you use? (3 points) Cement A: C3S=50 %, C2S= 25 %, C3A = 5%, C4AF = 20% Cement B: C3S= 55%, C2S = 25%, C3A = 10%, C4AF = 10% III) Describe the hydration reaction that generates the most heat. (3 points) IV) Describe Type IV cement. Why is it not available in the market anymore? (3 points)Question 2 (15 points) I) Explain when false set can occur. If false set develops in the field, what should you do? (5 points) II) You are working in a far away location where there is a shortage of potable water. There is plenty of water with a foul odor. List the two potential concerns of using this water for plain concrete. Describe the tests you should perform to verify that you can safely use for your job. (5 points) III) Normally we say that potable water can be used for concrete. Can you imagine an exception of this rule? (5 points)Question 3 (21 points) I) Draw a stress-strain diagram for: a) plain concrete, b) concrete with short fibers, c) concrete with long fibers, d) concrete with short and long fibers. (8 points) II) What are the diameter of this bar? (3 point) III) Of these mineral admixtures which ones are pozzolan; silica fume, slag, portland cement, fly ash, quartzitic sand, volcanic ash.(6 points) IV) Do the cement particles become hydrophilic or hydrophobic when plasticizers are used? (5 points)Question 4 (18 points) I) Fresh concrete containing air-entraining is often vibrated intensively. What prevents all the air-bubbles from a air-entraining admixture to coalesce and rise to the concrete surface? (5 points) II) Consider the mix design: Mix A (lb/yd3) Cement: 500 Gravel: 1327 Water: 250 To improve the workability of the concrete, you add 1% of plasticizer. Will the concrete strength increase compared to the strength of the original mix (6 points) II) Consider the two mix designs: Mix A (lb/yd3) Cement: 500 Gravel: 1327 Water: 250 Mix B (lb/yd3) Cement: 500 Fly ash 100 Gravel: 1327 Water: 250 Which mixture will have greater potential for cracking due to thermal stress? Justify your answer. (7 points)Question 5 (16 points) I) Can a plasticizer reduce bleeding of concrete? (4 points) II) Why is the concrete construction responsible for the generation of 7% of the CO2 emission? (4 points) III) Give three limitations of the slump test (4 points) IV) Last week during placement of the concrete, it developed flash set. What should you do to avoid the problem to happen again? (4 points)Question 6 (12 points) I) Discuss the potential advantages and disadvantages of using recycled rubber as an aggregate for concrete. (4 points) II) A concrete cube (3x3x3 in) containing 5% of air-entraining is placed in a cold room at 20 F. Will the cube increase or decrease its dimensions? (5 points) . III) Give the advantages and disadvantages of using belt conveyors to place concrete (3
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