Reference no: EM133002573

300984 Pavement Materials and Design - Western Sydney University

Asphalt Mix Design Practical

1.1 Objectives
In this practical, students will prepare and undertake Level 1 tests to evaluate the volumetric properties and determine the design bitumen content of a wearing course asphalt mix design for medium and heavy traffic categories.

1.2 Overview of practical

The class is divided into 4 groups. There are also four parts in this practical, each of approximately 30 mins duration. Each group will complete all 4 parts of the practical on a rotational basis.

(a) In Part A, students will prepare the aggregate materials for 3 asphalt specimens corresponding to bitumen content of 4%, 5% and 6% respectively.

(b) In Part B, the asphalt materials (aggregates and bitumen) will be compacted using the gyratory compactor to produce the 3 asphalt specimens of 4%, 5% and 6% bitumen content

(c) In Part C, students will determine the maximum density of the asphalt mixtures corresponding to 4%, 5% and 6% bitumen content based on AS/NZS 2891.7.3 (2014)

(d) Finally in Part D, the bulk density of the compacted asphalt specimens corresponding to 4%, 5% and 6% bitumen content will be determined using a presaturation procedure based on AS/NZS 2891.9.2 (2014).
After completion of the testing, the volumetric properties of the asphalt specimens (see Figure 1.1) will be evaluated for 4%, 5% and 6% bitumen content and the results used to determine the design bitumen content for the asphalt mix design based on the Level 1 tests.

2. Methods and Materials

Part A: Preparation of Aggregates for Asphalt Mix Design Specimens

2.A.1. Introduction
The basic components of asphalt mixture are generally coarse aggregate, fine aggregate, filler and bitumen. The performance of an asphalt mixture is considerably influenced by the proportions of the asphalt components and the properties of the asphalt constituents. The proportion of asphalt components affects different properties of final asphalt mixture, as illustrated in Figure 1.1 Therefore, it is essential to design an asphalt mixture with a right mix of all asphalt components.

In this test, 3 batches of aggregates will be prepared for the 3 different bitumen contents (4%, 5% and 6%) based on a selected grading target for the aggregates.

2.A.2. Procedure
Record results of this test in Datasheet No. A. 1 to A.3 (attached).

1) Calculate the required mass of aggregate for each fraction and the grading percentages based on the grading target and target bitumen content (4%, 5% or 65%) for each sample of total mass 1200 g.

2) Complete Datasheet No. A.1 for the 3 samples corresponding to bitumen content of 4%, 5%, and 6%.

3) Plot the grading envelopes and grading percentages for the 3 batches in Datasheet No.
A.2 (semi-logarithmic plot) to confirm the position of grading curve relative to gradation limits based on AS 2150 (Note: the 3 grading curves should lie within the grading envelopes).
4) Weigh the required mass of each fraction of the aggregates from the results in
Datasheet No. A.1.

5) Blend the aggregates by mixing the different fractions obtained in (4) to prepare 3 batches of aggregates corresponding to bitumen content 4%, 5% and 6%

6) Complete Datasheet No. A.3. to give the specifications for coarse aggregate (> 4.75 mm), fine aggregate (< 4.75 mm and > 75?m), filler (< 75?m) and bitumen components of the 3 batches.
2.A.2. Completion of Tasks in Part A
1) Complete Datasheet No. A.1 and A.3
2) Plot the gradation limit and aggregate gradations curves in Datasheet No. A.2 to show that the grading curves lie within the grading envelopes.

3) Blend the aggregates to prepare the three aggregate batches (for 4%, 5% and 6% bitumen content).

4) You MUST complete Tasks 1-3 and present them to the demonstrator before leaving Part A.

Part B: Compaction of Asphalt Test Specimens Using Gyratory Compactor set for Medium and Heavy Traffic Category

2.B.3.2. Test Procedure

1) When the asphalt is at the adequate temperature for required time, remove the heated mould and baseplate from the oven and place a circular paper disc in the bottom of the mould.

2) Place the test portion in a compaction mould and spade the asphalt with a heated spoon or spatula 15 times around the perimeter and 10 times over the interior.

3) Place the mould in the oven for sufficient time for the asphalt to reach the specified compaction temperature of 150°C. If it didn't reach the temperature after 60min, discard it.

4) Check the settings of the compactor. Set specimen diameter (100 mm), the required number of revolutions (80 cycles) or specified specimen height (65 mm), the gyratory angle (2°) and the vertical loading stress(240kPa), as presented in Table 1, on the gyratory compactor.

5) Remove the mould from oven. Place a thermometer in the mould and verify that the temperature in the mould is within the tolerance for compaction temperature, as presented in Table B.1. Record the temperature.

6) Place a circular paper disc, and then the upper wearing disc on the top of the mould.

7) Place the filled mould and assembly into the gyratory compactor and centre of the loading ram.

8) Immediately compact the specimen in the gyratory compactor until the nominal height of specimen is 65mm.

9) Record the height of the specimen at every 15 cycles in Datasheet No.1.

10) Remove the specimen from the mould using the specimen extractor. Care should be taken to ensure that the specimen has cooled sufficiently to ensure that it does not deform when removed from the mould. For this purpose, a cooling time of 5 to 10 minutes may be necessary.

11) Allow the specimen to cool.

12) Soon after the compacted bituminous mix specimens have cooled to room temperature, take the sample out of the mould using the sample extractor and measure the weight, average height around the circumference and diameter of the specimen.

13) Remove the paper disks from the top and bottom of the specimen.

14) Repeat steps 1 to 13 for all 3 asphalt specimens, and complete Datasheet No. B.1.

15) Based on the test results for the 3 samples, complete Datasheet No. B.1.

Part C: Determination of Maximum Density of Asphalt

2.C.2.3. Determination of the Maximum Density of Asphalt

The procedure shall be carried out for each test portion corresponding to bitumen content 4%, 5% and 6% as follows

1) Weigh a calibrated dry flask and record the mass (m1).

2) Place the test portion of asphalt in the flask, weigh and record the mass (m4).

3) Add sufficient methylated spirits to cover the test portion by about 25 mm. Carefully heat the flask on the hotplate until the methylated spirits is boiling freely but is not distilling out of the flask.

4) Carefully agitate the flask and contents until all occluded air in the sample has been displaced.

5) Remove the flask from the hotplate and allow it to cool in air for a few minutes and then in water.

6) Fill the flask with methylated spirits and immerse it up to the neck in the water bath for 10 mins (reduced from 1h due to time factor) or until a constant temperature of 25°C is obtained. If necessary, weigh down the flask to keep it firmly immersed.

7) Remove the flask to a level bench, carefully seat the capillary tube device on the flask and remove the excess of the methylated spirits by means of the suction pump.

8) Remove the capillary tube device. Then immediately and carefully dry the outside of the flask with paper towels.

9) Weigh the flask and contents and record the mass (m5).
NOTE: During the boiling process there is a tendency for some samples to coagulate, particularly if the bitumen content is high. To extract such samples from the flask at the end of the tests, the bulk of the methylated spirits should be poured out and the residue heated sufficiently to facilitate its removal.

10) Calculate the relevant parameters based on the given formula in section C.3, and complete Datasheet No. C. 1.

Part D: Bulk Density Test

Record results of this test in Datasheet No. D.1 (attached).

To save time 3 cylindrical samples of compacted asphalt mixtures containing different bitumen content (4%, 5% and 6%) (from Part B) have been pre-prepared and dried using vacuum desiccator based on the procedure described below.

The procedure shall be as follows:

1) Weigh the sample and record its dry mass (m1).

2) Immerse the sample in the water container for at least 5 min.

3) Position the water container directly beneath the balance and attached suspension device, and zero the balance.

4) Transfer the sample to the suspension device so that the sample remains completely immersed. Remove any air bubbles adhering to the sample and weigh. Record the mass (m2).

5) Remove the sample from the suspension device and surface-dry the specimen by blotting quickly with a damp towel.
NOTE: In blotting the surface, a damp cloth towel (not paper) should be used. The towel should be soaked and wrung between samples. The aim of blotting is to remove excess water beaded on the surface and is not meant to draw water from the void spaces of the sample. The desired action is to quickly and lightly blot the excess water from the sample, and determine the saturated surface dry mass as quickly as possible.

6) Weigh the wet sample and record the mass (m3).

7) Record the temperature of the water in the water container to the nearest 1°C.

Attachment:- Part_A_Table.rar