Civ E 391 Midterm Exam (Soils and Asphalt Concrete)

Transcription

1 Department of Civil Engineering Civ E 391 Midterm Exam (Soils and Asphalt Concrete) Time: 2.0 Hours Friday, November 2 nd, :00 8:00 PM Name: I.D. No.: Instructor: Dr. Vivek Bindiganavile Notes: 1. No notes or textbooks are permitted. 2. Only an approved non-prograable calculator is permitted. 3. Each question is of equal value. 4. Work on the available space of the question sheets (both sides). 5. Use pencil for answers and pen for name and signature. 6. This exam set has 12 sheets. Question Mark Total

2 Question 1 In the natural state, a moist soil has a volume of m 3 and weighs N. The oven dry weight of the soil is N. The specific gravity of the soil solids is Define each of the following parameters in terms of symbols and calculate the value for each based on the data above. a) Moisture Content (2 Marks) b) Moist Unit Weight (2 Marks) c) Dry Unit Weight (2 Marks) d) Void Ratio (2 Marks) e) Degree of Saturation (2 Marks)

3 Question 2 The particle size distributions of two soils are given in the Figure below. The results of the Atterberg test on the fine grain portion of the soils are given in the accompanying Table. Classify the soils by the Unified Soils Classification System. Provide a name for each soil. Show all your calculations. A USCS Chart and the Soil Classification Tree are attached. (10 Marks) Table-1: Atterberg Properties of Fines Soil A Soil B Liquid Limit (%) Plastic Limit (%) 22 20

4 Question 3 a. The temperature conditions at a site are given in Table 2 below. Table 2: Conditions for Performance Grading of Asphalt Binder Temperature data Mean Standard Deviation 7-day max. pavement temp. 57 C 2 C Minimum pavement temp. -6 C 3 C Based on the Binder Grades in the Performance Grade Specification (attached), select the appropriate grade for i) 50 % reliability and ii) 98% reliability. [4 Marks] b. Based on ASTM D 3381 (attached), examine each of the three asphalt samples shown in Table 3 and categorize according to the 3 Tables in that standard. Explain why, in case an asphalt sample cannot be graded. [6 Marks] Table 3: Asphalt Cement Test Results. (Note: Convert temperature from Celsius to Fahrenheit as T f = T c ) Properties Asphalt No. 1 Asphalt No. 2 Asphalt No. 3 Original Properties Viscosity at 60 o C, Poise Viscosity at 135 o C, centistoke Penetration, 25 o C, 100 g, 5 sec Flash point, o C Solubility in trichloroethylene, % After Thin Film Oven Aging Viscosity at 60 o C, Poise Ductility at 25 o C, 5 cm/min, cm After Rolling Thin Film Oven Aging Viscosity at 60 o C, Poise Viscosity at 135 o C, centistoke Penetration, 25 o C, 100 g, 5 sec Ductility at 25 o C, 5 cm/min, cm

5 (space for Question 3)

6 Question 4 Using the trial-and-error method, blend the three aggregates to meet the specification. Show all equations and at least one iteration. Indicate how you will proceed with further iterations if needed. [10 marks] Table 4: Properties of Aggregates (values indicate % passing through each sieve) Sieve Specification Aggregate Aggregate

7 Question 5 An aggregate blend is composed of 53% coarse aggregate by weight (specific gravity = 2.702), 43% fine aggregate (specific gravity = 2.621) and 4% ultra fine aggregate (specific gravity = 2.779). This blend is used to prepare asphalt concrete. The compacted specimen has a bulk specific gravity of and contains 6% asphalt binder (specific gravity = 1.052) by weight of the total mix. Ignoring binder absorption by the aggregate, compute: a) Voids in Total Mix; b) Voids in Mineral Aggregate; c) Voids Filled with Asphalt [10 Marks]

8 Question 6 Using only linear or bi-linear plots, indicate the relationship in each of the following graphs. [10 Marks] a) f) Flash Point Stability Maltenes in binder (%) % Asphalt Content b) g) Penetration G * sinδ (from DSR test) % of Asphaltenes in binder fatigue cracking c) h) Resistance to Rutting % of G % of crushed aggregates log 10 (number of gyrations) d) i) VMA Flow e) % of asphalt content j) Asphalt Content (%) No. of drops in Casagrade Device Viscosity Moisture Content in Soil (%) Maltenes Content (%)