Validation is one of the most important criteria in any research work. Any equipment needs to be validated with well-established and known methods. In this research work, an indigenously developed equipment called Roller Compactor cum Rut analyser (RCRA) is validated to ascertain that the required compaction is achieved.
The development of transportation infrastructure has been closely linked with the human development. Transportation plays a major role in the development of economy and there by overall development of the country. Road transportation is the most flexible mode of transportation which provides door to door service. With the emerging demand for the development of better roads, pavement types, better design and development has gained high importance.
Rheological properties of bituminous mix materials, climatic conditions, Construction practice severely affects the performance of bituminous pavements. In our country as well in many countries empirical Marshal Mix Method of mix design is being used. However, Marshal Method of Mix Design has its own drawbacks. In this direction to do the performance based pavement design an equipment called Roller Compactor and Rut Analyser is conceptualised, designed and fabricated indigenously, to have more practical approach to pavement testing and design.
A. Types of Pavement
Following are the main types of the pavements.
Semi rigid pavement
Flexible Pavement: Flexible pavements are those which are flexible in their structural action under the loads.
Some important features of these pavements are:
a. It has negligible flexural strength.
b. The deformation of the lower layers are reflected on the surface.
c. It will transmit the vertical load to bottom layers by grain to grain transfer.
d. The lower layer have to take up only lesser amount of stress, hence inferior materials with low cost can be used in the lower layers.
Flexible pavements consist of the following components.
Granular Sub base course
Bituminous Binder Course
Bituminous Surface Course
The main objective of this research work is to validate the compaction achieved for bituminous mix in Roller Compactor cum Rut Analyser.
B. ROLLER COMPACTOR CUM RUT ANALYSER (RCRA)
The Roller Compactor cum Rut Analyser (Fig 1) is an equipment for pavement testing and bituminous mix design. Using this equipment, the entire layers of pavement can be constructed and the materials can be tested for different parameter by applying wheel load to simulate the actual field condition
It consists of a main steel frame made of channel section fitted with scissors lifting mechanism to raise and lower the moulds. It has the provision for both compaction and rutting using the dedicated rollers. It has a control panel by which the different operations can be controlled.
The moulds are designed to build the different layers of pavement to bring the reality in the testing. The thickness of the different layers prepared/casted in RCRA moulds are as per the standard plates given in IRC 37-2012. The dimension of the mould used is 650 mm X 270 mm with varying heights. The compacted specimen of subgrade and bituminous layer is shown in Fig.2 and Fig.3 respectively.
The following methodology is adopted for validating the compaction achieved in the bituminous layers
The different layers of pavement namely Subgrade, Granular Sub Base (GSB) and Wet Mix Macadam (WMM) are casted in RCRA moulds as per the plates given in IRC37-2012.
DBM Grade-II and BC Grade –II layers are prepared in RCRA moulds.
Core of 100 mm diameter is extracted using core cutter machine.
The density of the specimen obtained by core cutting from the RCRA equipment and from Marshal Stability tests are compared and validated.
The aggregates are tested and results obtained shown in the Table.1
tests on aggregates
Name of the Tests
Permissible Limit (as per IS/MoRTH)
Aggregate Impact value test (AIV),%, max
Abrasion Value, %, max
Water Absorption,%, max
Shape Test, %, max
Plasticity Index, max
IS 2720-Part V
The bitumen binder used in the research work is VG-30. The tests are carried out as per relevant IS/ MoRTH specifications to confirm the suitability of bitumen to use in the bitumen mix (Table: 2)
table 2. tests on bitumen
Name of the test
Permissible values as per IS/ MoRTH
Penetration Value ,mm, min
Softening point ,ºC, min
Flash & Fire point ,ºC, min
274 and 300
Ductility value, cm, min
The obtained job Mix formula (JMF) for the DBM Gr-II is shown in Table No: 3
job mix formula for dbm grade-II
Percentages of different sizes of aggregates to be used as per JMF
20 mm & down Size
13.2 mm & down size
4.75 mm & down size
IV. EXPERIMENTAL RESULTS FOR MARSHAL MIX DESIGN
The Marshal Stability Test is conducted on two different mixes, namely,
DBM Grade II with VG-30,
DBM Grade II with 10% plastic with 3% Polyphosphoric Acid (PPA)
The obtained Results of Marshall Stability Test is given in the Table 4.
MARSHAL PROPERTIES FOR DIFFERENT TYPES OF BITUMINOUS MIX
10% Plastic and 3% PPA
Optimum Binder Content (OBC), %
Marshall Stability, kg
Flow Value, mm
Bulk Density, gm/cc
Volume of Voids, %
Voids in Mineral aggregate , VMA, %
Voids Filled with Bitumen, VFB, %
The specimens are casted in RCRA using the obtained Optimum Binder Content (OBC) and compacted using compaction mode to the required thickness. To validate the density achieved in RCRA equipment, a core of 100 mm dia is taken out using Core cutting machine and density is found. The obtained results are shown in Table No.5
COMPARISON OF DENSITY ACHIEVED
Obtained results in Marshall Stability
Obtained results in RCRA equipment
Percentage of Compaction/ Density achieved
Obtained results in RCRA
Percentage of Compaction/ Density achieved
10% Plastic and 3% PPA
From the laboratory investigation it can be concluded that the compaction achieved in the RCRA for bituminous mix is more than 98 percent which is obtained by using Marshall Stability method. This proves that, the required density of more that 98% which is required in the field, is achieved by using RCRA equipment in the laboratory.
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 V.Suganpriya, S.OmPrakash, V.Chandralega “Study of behavior of bitumen modified with crumb rubber” IJERT Vol 5, issue 5, May-2016.
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