CIVIL 767 – ADVANCED PAVEMENT ENGINEERING PAVEMENT MATERIALS AND DESIGN

Assignment 1 Question 1 State whether this statement is true or false and explain your answer using equations. “In pavement structural design, it is always safe to assume that tyre contact pressure is equal to tyre inflation pressure.” Question 2 List three different distress mechanisms of flexible pavement. Briefly discuss the causes of these distresses. Question 3 Samples of coarse aggregate from a stockpile are brought to the laboratory for determination of specific gravities. The following weights are found: Mass of moist aggregates samples as brought to the lab : 5298g Mass of oven dried aggregates (A): 5216 g Mass of aggregates submerged in the water (C): 3295 g Mass of SSD (Saturated Surface Dry) aggregates (B) : 5227 g Find:

a) the aggregate bulk specific gravity b) the aggregate apparent specific gravity c) the moisture content of stockpile aggregate(report as a percent) d) Absorption(report as percent)

Question 4 Use the trial and error method to blend the three aggregates A,B and C to achieve the mid point specification shown in the table below. If Aggregates A , B and C have specific gravities 2.77, 2.89 and 3.15, determine the specific gravity of the blend. Aggregate A Aggregate B Aggregate C Specification

25 100 100 100 94-100 12.5 63 100 100 70-85 4.75 19 100 100 40-55 2.36 8 93 100 30-42 0.6 5 55 100 20-30

0.15 3 36 97 12-22 0.075 2 3 88 5-11

Question 5 What are the objectives of the asphalt concrete mix-design process? Question 6 For a asphalt concrete define

a) Air Voids b) Voids in the mineral aggregates

Voids filled with asphalt

Question 7 As part of mix design, a laboratory-compacted cylindrical asphalt specimen is weighed for determination of bulk specific gravity. The following numbers are obtained:

Dry mass in air = 1204.5 grams Mass when submerged in water = 689.4 grams Mass of saturated surface dry (SSD) = 1211.3 grams

a. What is the bulk specific gravity of the compacted specimen (Gmb) b. If the maximum theoretical specific gravity of the specimen (Gmm) is

2.531, what would be the air void content of the specimen in percent? Question 8 An aggregate blend is composed of 53% coarse aggregate by weight (Sp. Gr. 2.702), 43% fine aggregate (Sp. Gr. 2.621), and 4% filler (Sp. Gr.2.779). The compacted specimen contains 6% asphalt binder (Sp. Gr.1.052) by weight of total mix, and has a bulk density of 2.327 g/cm3. If bitumen absorption is given as : Case 1: Pba=0.0% Case 2: Pba=0.7% by mass of aggregates, Compute the percent voids in the total mix, percent voids in mineral aggregates, and the percent voids filled with asphalt. Question 9 An asphalt concrete specimen has the following properties: Asphalt content = 5.3% by total weight of mix Bulk specific gravity of the mix = 2.442 Theoretical maximum specific gravity = 2.535 Bulk specific gravity of aggregate = 2.703 Calculate the percents VA, VMA, and VFB. Question 10 Both fine and coarse grained unbounded materials behave in nonlinear manner. Explain the differences between linear and nonlinear behavior. Explain also, using graphs, the difference in the nonlinear behavior between fine and coarse grained materials. Question 11 As part of a quality control test, the site engineer cut out cylindrical core of asphalt concrete with 12.5 mm maximum nominal aggregate size. In addition to the core, some other amounts of asphalt mix were removed to carry out some volumetric tests for both compacted and loose mix. The results of the volumetric testing for the compacted core and that for the loose mix are shown in Table 1 and Table 2, respectively. If the percentage of bitumen by weight of the total mix is 5.0%, the aggregate bulk specific gravity is 2.65, bitumen specific gravity is 1.02, determine:

a. The maximum theoretical specific gravity of the mix b. Percent of bitumen absorbed

c. Effective specific gravity. d. the percentage of air voids e. the percentage of voids filled with bitumen f. the percentage of voids filled with bitumen g. The effective bitumen content. h. If this mix is intended for heavy traffic, comment on suitability of the mix in regard of the percentage of air voids, voids in the mineral aggregates, and voids filled with bitumen. Are there any expected problems with using such mix? Table 1 Results of the compacted Sample

Dry mass of the core in air (grams)

SSD mass of the Core in Air (grams)

Submerged mass of the core in (grams)

1250 1251 740.491 Table 2 Results of the uncompacted mix

Measured Value Mass in grams Mass of empty pycnometer, m1 3050.00 Mass of Pycnometer plus water, m2 7244.50 Mass of pycnometer plus loose mix, m3 4504.00 Mass of pycnometer plus water plus loose mix, m4 8125.60

Question 12 In Marshall mix design, laboratory tests showed that the specific gravity of bitumen is 1.03, while the bulk specific gravity of aggregates is 2.674. The percentage of bitumen absorption is 0.6% of the dry weight of aggregates and the effective specific gravity is 2.717. The data for bulk specific gravity of the compacted specimens, stabilty and flow are shown in the Table 3 below.

1. Draw the relationship between bitumen content and each of the following parameters:

• Flow • Stability • Bulk density • Air voids • Voids in Mineral aggregates • Voids filled with bitumen

2. Determine the optimum bitumen content if the pavement is expected to carry heavy traffic volume and the maximum nominal size of aggregate particles is 19 mm.

Table 3: Marshall Mix Design Data

%BC Mass of Compacted Specimen Stability

(kN) Flow (0.25 mm)

Air Submerged SSD

3.5 1240.6 726.4 1246.3 11 8 1238.7 723.3 1242.6 10.8 7 1240.1 724.1 1245.9 11.2 7

4.0 1244.3 727.2 1246.6 9.7 9 1244.6 727 1247.6 10.1 9 1242.6 727.9 1244 10.3 8

4.5 1249.3 735.8 1250.2 10.8 9 1250.8 728.1 1251.6 10.7 9 1251.6 735.3 1253.1 10.4 9

5.0 1256.7 739.8 1257.6 10.2 9 1258.7 742.7 1259.3 9.7 8 1258.4 737.5 1259.1 10.0 9

5.5 1263.8 742.6 1264.3 9.8 9 1258.8 741.4 1259.4 10.2 10 1259.0 742.5 1259.5 9.80 9

Question 13 a. What are the main criteria for designing open graded asphalt mixes? b. What is the philosophy of the SMA design, in particular that which relates to

aggregate gradation? Describe the NCAT method to achieve this goal. c. Referring to the SUPERPAVE characterisation tests for bitumen, clearly define

each of the following parameters, how they are measured and state their significance. If there are any upper or lower limits of these parameters in order to control pavement performance, clearly state these values and show the reasons for them.

i Creep Stiffness ii “m-value” d. Define the parameters G* and δ. and what equipment is required to measure

them?

e. The two parameters ( )G *

sin δ and ( )G *sin δ are used to detect the properties of

bitumen that affect two modes of failure of asphalt mixes. Explain in detail the above statement, stating the values of these two parameters in order to control the associated modes of failure.