Hamburg wheel tracking test according to EN 12697-22 and AASHTO T324 | Công ty cổ phần đầu tư xây dựng BMT

Hamburg wheel tracking test according to EN 12697-22 and AASHTO T324

Date: 08-07-2013

Laboratory wheel-tracking devices are used to run simulative tests that measure HMA qualities by rolling a small loaded wheel device repeatedly across a prepared HMA specimen. Performance of the test specimen is then correlated to actual in-service pavement performance. Laboratory wheel-tracking devices can be used to make rutting, fatigue, moisture susceptibility and stripping predictions.

There are several different types of wheel-tracking devices: Asphalt Pavement Analyzer (APA); Hamburg Wheel Tracking Device (HWTD); French Rut Tester (FRT). Among these devices, HWTD is used more popularly than the others. Hamburg wheel track test is required in almost standards and specifications for hot mix asphalt in Europe, America…

Nowadays, rutting deformation is happening on all main road in Vietnam. The laboratory wheel track test is very necessary and important to estimate rutting resistance of hot mix asphalt. In 2011, Institute of Transport Science and Technology of Ministry of Transport have required Hamburg wheel track testing of compacted hot mix asphalt in TCVN 8819:2011.

Figure 1 – Hamburg Wheel Tracking Device (HWTD)

Figure 2 – (French Rut Tester (FRT)

Figure 3 – Asphalt Pavement Analyzer (APA)

For this testing, all laboratories on the world are applying the Europe standard EN 12697-22 and US standard AASHTO T324. Basically, these standards are the same although they have some different points, which is shown on below table.

Table – EN 12697-22 vs AASHTO T324 and BMT Laboratory Testing

Technical characteristic

TP Asphalt-StB (based on 12697-22) (2007)

AASHTO T324-04

BMT Laboratory

1

Device

Hamburg wheel tracking device (HWTD).

The divice has thermostatic system for air condition and water bath.

Hamburg wheel tracking device (HWTD 2012– Infratest, Germany).

The divice has thermostatic system for air condition and water bath.

2

Functions

Testing the rutting, moisture-susceptibility, stipping inflection point of HMA

3

Wheels

Steel wheels of rubber wheels:

  • Steel wheels: diameter 203±2 mm; width 50±5 mm, rectangular cross section.
  • Rubber wheels: ruber width: 20±2 mm; wheel width 50±5 mm; rectangular cross section.
Steel wheels diameter 203.2 mm, width 47 mm.

Steel wheels of rubber wheels:

  • Steel wheels: diameter 203 mm; width 47 mm, rectangular cross section.
  • Rubber wheels: ruber width: 20±2 mm; wheel width 50±5 mm; rectangular cross section.

4

Wheel load

700±10 N

705±4.5 N.

710 N

5

Speed

53 crossings/min

50 crossings/min.

53 crossings/min

6

Testing environment

Air or water

Water

Air or water

7

Testing temperature

60oC. Thermalizing time depends on sample thickness:

h ≤ 60 mm – 4h;

h > 60 mm – 6h.

40-50oC or temperature specified for the binder being used. 60oC (temperature specified from 30 – 70oC according to pavement condition in idividual region).

8

Specimen

  • Slab specimen 320×260 mm
  • Core specimen diameter at least 300 mm.
  • Specimen height depends on nominal maximum size of aggregate.
  • Compraction factor based on Marshall sample unit weight: 99 – 101 %.
  • Saw-cut slab sprcimen 320×260 mm, height at least 25 mm.
  • Field core diameter at least 300 mm, height at least 25 mm.
  • Slab specimen 320×260 mm (Kneading Compactor or equivalaent compactor), height 38-100 mm. Height is at least twice the nominal maximum size of aggregate.
  • Superpave Gyrator Specimen, height 38-100 mm.
  • Two specimens diameter 150 mm.
  • Field core diameter 250 mm.
  • Saw-cut slab sprcimen 320×260 mm.
  • Height of saw-cut or field core specimens 38 – 100 mm, typically 38 mm
  • Slab specimen 320×260 mm prepared from automatically roller sector compactor.
  • Height: 40 – 120 mm depending on the nominal maximum size of aggregate.
  • All specimens according to EN 12697-22 and AASHTO T324
   
9 Result
  • Measurement system guarantee the rutting depth with accuracy 0.01mm.
  • The device shall shut off when the rutting depth is more than 20% specimen height after 10.000 crossings.
  • Measurement system guarantee the rutting depth with accuracy 0.01mm.
  • The device shall shut off when 20.000 crossings have occurred; the rutting depth is 40.90 mm or greater for an individual specimen.
  • Measurement system guarantee the rutting depth with accuracy 0.01mm.
  • The device shall shut off when the installed crossing number have occurred (typically 20 000 crossings); or rutting depth is greater installed value (typically 25 mm).
   

Figure 4 – Slap specimen 230×360 mm

Figure 5 – Superpave Gyrator core specimen

Research & Development and Testing department

Dr. Vo Dai Tu

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