ABSTRACT
Chapter 8 includes questions and problems that cover the important aggregate properties, particularly the Superpave properties, minimum requirements, and criteria. Aggregate properties concern highway engineers as aggregate compose approximately 95% of the design of asphalt mixtures used in the construction of asphalt pavements in highways. Consequently, the control of these properties and the assurance of high-quality aggregate properties are crucial in order to obtain the best results in mixture design and construction. The questions and problems in the following section will encompass the key properties of aggregate used for highway construction.
In a flat and elongated (F&E) particles test for a coarse aggregate sample, the results shown in Table 8.1 are obtained. Determine the F&E value for this coarse aggregate sample, if this aggregate is to be utilized in the design of asphalt mixture that will be used in the construction of a road with 2 million equivalent single-axle loads (ESALs).
Solution:
The percentage of F&E particles is calculated using the formula shown below:
% F & E = F E F E + N × 100 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0001.tif"/>
Where:
FE = count or weight of particles that are flat, elongated, or flat and elongated,
N = count or weight of particles that are neither flat, elongated, nor flat and elongated.
Therefore,
% F & E = 6 + 4 + 8 6 + 4 + 8 + 82 × 100 % = 18 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0002.tif"/>
Since the traffic loading of the road is 2 million ESALs ≥ 1 million ESALs, according to Table 8.2 (the Superpave F&E Criteria), the maximum F&E value is 10%. The F&E value obtained in this problem (18%) is higher than 10%; and therefore, the coarse aggregate is rejected based on the F&E criteria.238
The MS Excel worksheet used to solve this problem is shown in Figure 8.1.
If the coarse aggregate angularity (CAA) of a coarse aggregate sample is recorded as 90/84, determine the following:
The percentage of aggregate particles with zero fractured faces
The percentage of aggregate particles with only one fractured face
Solution:
Since CAA = 90/84, 90% of the coarse aggregate particles has one or more fractured faces, and 84% of coarse aggregate particles has two or more fractured faces. This concludes that 100−90 = 10% of aggregate particles has zero fractured faces.
In a similar manner: since 90% of the coarse aggregate particles has one or more fractured faces and 84% of coarse aggregate particles has two or more fractured faces, then 90−84 = 6% of aggregate particles has only one fractured face.
The MS Excel worksheet used to solve this problem is shown in Figure 8.2.239
In a coarse aggregate angularity (CAA) test for a coarse aggregate sample, the results shown in Table 8.3 are obtained. Determine the CAA value for this coarse aggregate sample. If this coarse aggregate is to be used in the design of an asphalt mixture, can this mixture be used in the construction of a 5-cm surface course for a road pavement with 5 million ESALs?
Solution:
The CAA value of aggregate is determined by calculating the percentage of aggregate particles having one or more fractured faces and the percentage of aggregate particles with two or more fractures faces. Hence, according to given data in the table, the percentage of particles with one or more fractured faces is calculated as below:
Weight of Particles with ≥ 1 FF = 50 + 70 + 100 + 250 = 470 g https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0003.tif"/>
Weight of Particles with ≥ 2 FF = 70 + 100 + 250 = 420 g https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0004.tif"/>
Total Weight of Sample = 30 + 50 + 70 + 100 + 250 = 500 g https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0005.tif"/>
%Aggregate Particles with ≥ 1 FF = Weight of Particles with ≥ 1 FF Total Weight of Sample × 100 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0006.tif"/> 240
⇒
% Particles with ≥ 1 FF = 470 500 × 100 % = 94 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0007.tif"/>
%Aggregate Particles with ≥ 2 FF = Weight of Particles with ≥ 2 FF Total Weight of Sample × 100 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0008.tif"/>
⇒
%Particles with ≥ 2 FF = 420 500 × 100 % = 84 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0009.tif"/>
Hence, % CAA = 94/84
For a 5-cm surface layer with 5 million ESALs (3−< 10 million ESALs), the Superpave CAA criteria specify a minimum value of 85/80 as shown in Table 8.4. Since the CAA value determined for this coarse aggregate is 94/84, which is higher than 85/80, the asphalt mixture produced using this aggregate can be used for the construction of the 5-cm surface layer for the road pavement with 5 million ESALs.
The MS Excel worksheet used to solve this problem is shown in Figure 8.3.241
In a fine aggregate angularity (FAA) test, the mass of the fine aggregate sample is measured to be 145.0 g. If the bulk specific gravity of the fine aggregate is 2.452, then calculate the FAA (%) value of the aggregate. Based on this result, determine if this aggregate can be used for the same surface layer in Problem 3.3 above.
Solution:
UVC = V − M G sb V × 100 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0010.tif"/>
Where:
UVC = uncompacted void content or FAA of fine aggregate sample (%),
V = volume of cylinder used in the FAA test (standard volume = 100 cm3),
M = mass of fine aggregate sample,
Gsb = specific gravity of fine aggregate.
Therefore:
UVC = 100 − 145 2.452 100 × 100 % = 40.9 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0011.tif"/>
For a 5-cm surface layer with 5 million ESALs (3−< 10 million ESALs), the Superpave FAA criteria specify a minimum value of 45% as shown in Table 8.5. Since the FAA value determined for the fine aggregate in this problem is 40.9%, which is lower than the Superpave minimum requirement, the asphalt mixture produced using this aggregate is not suitable for the construction of this pavement layer.242
The MS Excel worksheet used to solve this problem is shown in Figure 8.4.
In a fine aggregate angularity (FAA) test, if the FAA is 50%, the volume of the cylinder is 100 cm3, and the bulk specific gravity of the aggregate is 2.590, determine the measured mass of the fine aggregate sample in the cylinder in grams.
Solution:
Using the same formula as above,243
UVC = V − M G sb V × 100 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0012.tif"/>
⇒
M = ( V − UVC × V 100 ) G sb https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0013.tif"/>
⇒
M = ( 100 − 50 × 100 100 ) 2.590 = 129.5 g ( 0.286 lb) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0014.tif"/>
The MS Excel worksheet for this problem is shown in Figure 8.5.
A 134-g sample of fine aggregate is tested for FAA to have uncompacted void content of 44%. Determine the specific gravity of the fine aggregate.
Solution:
Using the same formula
UVC = V − M G sb V × 100 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0015.tif"/>
⇒
G sb = M ( V − UVC × V 100 ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0016.tif"/> 244
⇒
G sb = 134 ( 100 − 44 × 100 100 ) = 2.393 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0017.tif"/>
The MS Excel worksheet used to solve this problem is shown in Figure 8.6.
Determine the sand equivalent (SE) of a fine aggregate sample if the clay reading and the sand reading are 5.1 and 4.6 inches (11.7 and 13.0 cm), respectively. Based on this result, is this aggregate suitable to be used for the same road pavement as in Problem 8.3 above? Explain why.
Solution:
SE = Sand Reading Clay Reading × 100 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0018.tif"/>
Where:
SE = sand equivalent (%),
Sand reading = the reading of the sand in the SE graduated container (inches),
Clay reading = the reading of the clay in the SE graduated container (inches); this reading is composed of the sand reading plus the height of the clay in the container.
⇒
SE = 4.6 5.1 × 100 % = 90.2 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0019.tif"/> 245
The Superpave SE criteria specify a minimum value of 45% for the SE at a traffic level of 3 − < 10 million ESALs as shown Table 8.6. Since the SE value obtained is 90.2%, which is higher than the Superpave minimum requirement (45%), the fine aggregate can be used for the specified surface layer.
The MS Excel worksheet used to solve this problem is shown in Figure 8.7.
In a sand equivalent (SE) test for a fine aggregate sample, the SE is determined to be 60%. If the sand reading is 4.5 inches (11.4 cm), determine the clay height.
Solution:
SE = Sand Reading Clay Reading × 100 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0020.tif"/>
⇒
Clay Reading = Sand Reading × 100 SE https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0021.tif"/> 246
⇒
Clay Reading = 4.5 × 100 60 = 7.5 in ( 19.1 cm) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0022.tif"/>
But the clay reading is composed of the sand reading plus the clay height. Therefore:
Clay Reading = Sand Reading + Clay Height https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0023.tif"/>
⇒
7.5 = 4.5 + Clay Height https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0024.tif"/>
⇒
Clay Height = 3.0 in ( 7.6 cm) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/TNF-CH008_eqn_0025.tif"/>
The MS Excel worksheet used to solve this problem is shown in Figure 8.8.247 248
In Table 8.7, the percent passing for an aggregate blend is given. Determine the following:
The nominal maximum aggregate size (NMAS)
The maximum aggregate size of this aggregate
The percentage of coarse aggregate
The percentage of fine aggregate
The percentage of filler material
Solution:
The nominal maximum aggregate size (NMAS) is defined as the first sieve size above the sieve size that retains more than 10% (percent passing < 90%). The sieve size that retains more than 10% is 9.5 mm. The first sieve above this sieve is 12.5 mm. Hence, 12.5 mm is the NMAS.
The maximum aggregate size is the sieve size above the NMAS. Therefore, it is 19.0 mm.
The coarse aggregate is that portion of the material retaining on sieve No. 4 (4.75 mm). Therefore, the percentage of coarse aggregate in this case = 100−65 = 35%.
The fine aggregate is that part of the material passing sieve No. 4 (4.75 mm). Hence, the percentage of fine aggregate in this case = 65%.
The filler material is that portion passing sieve No. 200 (0.075 μm). In other words, it is equal to 4%.
Flat and Elongated Particles Test Data for a Coarse Aggregate Sample Category Flat Elongated Flat and Elongated Neither Flat nor Elongated Count of Aggregate Particles 6 4 8 82 Superpave F&E Particles Criteria Traffic (million ESALs) Maximum, % < 1 -- ≥ 1 10 Reproduced with permission from Superpave Mix Design SP-2, 2001, by Asphalt Institute, Lexington, Kentucky, USA. MS Excel worksheet image for the computations of Problem 8.1. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/fig8_1_B.tif"/> MS Excel worksheet image for the computations of Problem 8.2. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/fig8_2_B.tif"/> Coarse Aggregate Angularity (CAA) Test Data for a Coarse Aggregate Sample FF* 0 FF 1 FF 2 FF 3 FF 4 FF Weight of Aggregate Particles (g) 30 50 70 100 250 *Note: FF = Fractured Faces. Superpave CAA Criteria Traffic (million ESALs) Depth from Surface < 100 mm > 100 mm < 0.3 55/-- --/-- 0.3 − < 1 65/-- --/-- 1 − < 3 75/-- 50/-- 3 − < 10 85/80 60/-- 10 − < 30 95/90 80/75 30 − < 100 100/100 95/90 ≥ 100 100/100 100/100 Reproduced with permission from Superpave Mix Design SP-2, 2001, by Asphalt Institute, Lexington, Kentucky, USA. MS Excel worksheet image for the computations of Problem 8.3. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/fig8_3_B.tif"/> Superpave Fine Aggregate Angularity (FAA) Criteria Traffic (million ESALs) Depth from Surface < 100 mm > 100 mm < 0.3 -- -- 0.3 − < 1 40 -- 1 − < 3 40 40 3 − < 10 45 40 10 − < 30 45 40 30 − < 100 45 45 ≥ 100 45 45 Reproduced with permission from Superpave Mix Design SP-2, 2001, by Asphalt Institute, Lexington, Kentucky, USA. MS Excel worksheet image for the computations of Problem 8.4. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/fig8_4_B.tif"/> MS Excel worksheet image for the computations of Problem 8.5. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/fig8_5_B.tif"/> MS Excel worksheet image for the computations of Problem 8.6. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/fig8_6_B.tif"/> Superpave Sand Equivalent (SE) Criteria Traffic (million ESALs) Minimum SE Value (%) < 3 40 3 − < 30 45 ≥ 30 50 Reproduced with permission from Superpave Mix Design SP-2, 2001, by Asphalt Institute, Lexington, Kentucky, USA. MS Excel worksheet image for the computations of Problem 8.7. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/fig8_7_B.tif"/> MS Excel worksheet image for the computations of Problem 8.8. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429054297/5885f92e-b0a3-419d-837a-bad4e02024b0/content/fig8_8_B.tif"/> Gradation (Sieve Size and Percent Passing) for an Aggregate Blend Sieve Size (mm) % Passing 25.0 100 19.0 96 12.5 92 9.5 75 4.75 65 2.36 55 1.18 44 0.600 33 0.300 22 0.150 12 0.075 4