9. PA 9 solutions PDF

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Tutorial solutions covering material from lectures 15 and 16 ...

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Lecture 17 (Masonry) 1. Discuss the difference between a hollow unit and a solid unit.? A masonry unit in which the net cross-sectional area is less than 75% of the gross area is called a hollow unit; when it is equal to or more than 75% it is called a solid unit. 2. What are the four type of standard mortar? Type M, Type S, Type N and Type 0 are the four standard mortars. 3. What is efflorescence? The process in which patches of salts are deposited on the surface of masonry due to evaporation of moisture is called efflorescence. 4. A concrete masonry unit is tested for compressive strength and produces the following results: Failure load = 726 kN Gross area = 0.081 m2 Gross volume = 0.015 m3 Net volume = 0.007 m3 Is the unit categorized as solid or hollow? Why? What is the compressive strength? Does the compressive strength satisfy the ASTM requirements for load bearing units shown in Table 8.2?

Percentage of net cross-sectional area = (0.007/ 0.015) x 100 = 46.67% < 75% Therefore, the unit is categorized as hollow. Net area = 0.081 x 0.4667 = 0.0378 m2 Compressive stress = 726 / 0.0378 = 19.21 kN/m2 ( 19.21 MPa) > 11.7 MPa (Table 8.2) Thus, the compressive strength satisfies the strength requirements. 5. A half-block concrete masonry unit is tested for compressive strength. The outside dimensions of the specimen are 190 mm * 190 mm * 190 mm. The cross section is a hollow square with a wall thickness of 25 mm. The load is applied perpendicular to the hollow cross section and the maximum load is 225 kN. a. Determine the gross area compressive strength. Gross area compressive strength = P/Agross = 225 /(190 x 190) = 6.2 MPa b. Determine the net area compressive strength. Net area compressive strength = P/Anet = 225 /(140 x 140) = 11.5 MPa

6. A symmetrical hollow concrete masonry unit, with a cross-sectional area as shown in Figure P8.7, is tested for compressive strength. The compressive load at failure is 329 kN. What is the compressive strength in MPa?

Gross area = 0.290 x 0.190 = 0.0551 m2 Net area = 0.250 x 0.150 = 0.0375 m2 Percentage of net cross-sectional area = (0.0375 / 0.0551) x 100 = 68.1% < 75% Therefore, the unit is categorized as hollow. Compressive stress = 329 / 0.0375 = 8,773.33 kN/m2 = 9.0 MP MPa a Lecture 18 (Bituminous) 1. What are the three types of asphalt? Asphalts are manufactured and sold as asphalt cement, cutback asphalt, and emulsified asphalt. 2. What is a slurry seal? Discuss its common use? A slurry seal is a mixture of emulsified asphalt, well-graded fine aggregate (sand) and mineral filler (Portland cement). Used to fill cracks and voids and gives a new surface to the pavement. Used on light traffic roadways. a slurry seal contains aggregate and can correct minor surface defects-filling cracks and voids. 3. What is emulsified asphalt? Produced by dispersing water in asphalt as an emulsion. water is the continuous phase and asphalt is the dispersed phase 4. Explain what is meant by temperature susceptibility of asphalt cement and the temperature effect on AC. Asphalt is highly affected by temperature. Asphalt shows too brittleness in law temperature where thermal cracks can occur and become too soft in high temperature where rutting can happen. Degree of susceptibility is the slope of viscosity vs temperature graph....