300984 Pavement Materials and Design Asphalt Mix Design Practical

Pavement Materials and Design Asphalt Mix Design Practical 

1. Asphalt Mix Design Practical Overview

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

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