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Berkeley CIVENG 165 - EXAMINATION

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UNIVERSITY OF CALIFORNIA AT BERKELEY CEE SPRING SEMESTER, 2008 Instructor: P.J. M. Monteiro Name:_____________________ CE 165 - EXAMINATION Please justify your answer in all the questions Question 1(14 points) I) Which is the first hydration product to form in portland cement? (3 points) II) Gypsum is added to clinker to control the hydration of tricalcium aluminate. Do you expect to see the presence of gypsum in concrete after 2 months? (4 points) III) Draw the strength evolution for a concrete made with calcium aluminate cement. (4 points) IV) Which cement mineral has to be reduced or eliminated to produce white cement? (3 points)Question 2 (23 points) I) Your company has just bought a new high resolution microscope. Describe to the microscope operator what compounds you expect to see in a 30-days old cement paste. (6 points) II) Sketch a graph of the heat of hydration of a blended portland cement as a function of the pozzolan content in the cement. (5 points) III) Draw the evolution of the amount of calcium hydroxide for a) Portland cement and b) Type-IP cement. (6 points) IV) Oil-well cements are used in the petroleum industry. Temperature and pressure can affect the workability of the paste during the cementing of oil pipes. List two possible modifications to a regular cement to minimize the reduction in workability. (6 points)Question 3 (18 points) I) When added to concrete would citric acid (see chemical formula below) act as an air-entraining admixture or a plasticizer? (4 points) CH2COOHCH2COOHCOOHHOC II) Explain what surface tension is. What are the units of surface tension? (6 points) III) What are the differences between Fly Ash F and C? (4 points) IV) Describe how rice husk ash is produced and how it affects the properties of concrete (4 points)Question 4 (27 points) I) A concrete sample containing 5% entrained air has a density of 150 pcf. Estimate the number of entrained air voids per cubic yard of concrete. (7 points) II) After placing the concrete in a column. Somebody noticed that the concrete had 25% more retarding admixture than originally designed. Write a memo describing the consequences of this mistake and the options that the contractor has to deal with the problem. (6 points) III) A concrete mixture was designed to have a large amount of entrained air (8%). During casting the temperature dropped faster than expected and within 4 hours the concrete was exposed to freezing temperatures. The contractor calmed down the owner by explaining that the large amount of air voids will protect the concrete. Write a memo supporting or criticizing the contractor’s argument. (6 points) IV) “Green concrete” uses over than 50% fly ash. As discussed in class fly ash does not provide high early strength in the early ages. Describe modification in the mix design that could increase the early strength of the concrete. (6 points)Question 5 (20 points) I) Explain why contractors often will allow only a maximum 2% of fibers in a concrete mix proportion. (4 points) II) Describe the following terms: laitance, crazing, plastic shrinkage. (6 points) III) You’re working in a concrete laboratory and your boss asks you to develop tests to measure a) bleeding and b) segregation of concrete. Write a memo (not to worry, it will be the last memo of this exam…) describing you could perform these tests. (6 points) IV) Explain the differences between central-mixed concrete and truck-mixed concrete. (4


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Berkeley CIVENG 165 - EXAMINATION

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