Bituminous / Asphalt Premix

The suitable bitumen content for a bituminous paving mixture was determined through laboratory Marshall Design method. The optimum bitumen content obtained from this method will be used as a guide to produce hot mix asphalt at a premix plant. To ensure the bitumen content used in the paving mixture is as designed, extraction of bitumen form bituminous paving mixture has to be conducted. This is carried out for the purpose of specification acceptance, quality control and assessment, and research.
This test is done to determine the bitumen content as per ASTM 2172. The apparatus needed to determine bitumen content are:-
i) Centrifuge extractor
ii) Miscellaneous – bowl, filter paper, balance and Methyaline Chloride

The Marshall Stability and Flow test is done to determine the Marshall stability and Flow of bituminous mixture as per ASTM D 1559. The principle of this test is that Marshall Stability is the resistance to plastic flow of cylindrical specimens of a bituminous mixture loaded on the lateral surface. It is the load carrying capacity of the mix at 60°C and is measured in kg. The apparatus needed to determine Marshall Stability of bituminous mixture is

1. Marshall stability apparatus
2. Balance and water bath

The sample needed is From Marshall stability graph, select proportions of coarse aggregates, fine aggregates and filler in such a way, so as to fulfill the required specification. The total weight of the mix should be 1200g.

The Marshall Test is used to measure physical properties of asphalt specimens that relate to plastic deformation properties of asphalt mixes. The test is carrying out using automatic Marshall Compactor. It automatically compact the specimen and stops off the motor after the preset number of strokes has been completed on the automatic digital display counter. The trip mechanism is structured so that the hammer falls at the same height at every stroke. The drive mechanism lifts the 4.53 kg compaction hammer plated against corrosion, to the height of 457+3mm and allows free fall at 75 blows each side. At least 3 parallel test specimens should be prepared. Each specimen requires approximately 1200g of bituminous material and heats the individual 1200g samples in a 140°C (285°F) oven. The mass required should be adjusted so that ach test specimen has a height of 63.5 ± 1.3 mm after compaction. Immediately after compaction, remove the compacted specimen from the mold and allow it to cool to room temperature.

The design of hot mix asphalt mixes involves determining an economical blend of aggregates that provides a combined gradation within the limits of the specifications and a determination of the percent of asphalt binder to mix with the aggregate blend, which provides a mix, which meets volumetric specifications. Trial mixes prepared with different binder contents are tested for mix properties (approximately 15 samples are required to be prepared) and the results are analyzed to select the optimum binder content (OBC) that is judged to be most satisfactory for the intended use of the mix.

Asphaltic Concrete coring of the existing pavement surface takes all the guesswork out of the equation and provides the proper method for any construction or maintenance that may be required. Asphaltic Concrete coring test is an extremely precise tool used during new construction to verify quality, as well as a tool to evaluate existing asphalt pavements for potential problem with asphalt and base material. Core testing provide the most accurate in-place information. Soil classification and thickness of pavements are important variable to understand when planning a paving project.
The core testing can provide information to determine pavement thickness, bond between pavement layers and soil type under pavement.

Samples of asphalt concrete collected using the coring method may be used to evaluate various characteristics of an asphalt concrete pavement for construction quality control testing, quality assurance testing and product acceptance testing. Core samples may also be used for research testing purposes.
Cores are extracted from a pavement after the pavement is laid, thus making it a destructive process. Bulk specific gravity measurements are then made on the cores in a laboratory. The methods of measuring bulk specific gravity of cores include:
a) saturated surface-dry method