Hamburg Wheel-Track Testing (Rutting Test) of Asphalt AASHTO T-324 BY Maawa World

AASHTO T 324, Hamburg wheel-track testing, moisture sensitivity, micromechanics finite element, three-stage Weibull, asphalt, pavement. The Hamburg Wheel-Track Device (HWTD) test has recently gained popularity among many state highway departments of transportation (DOTs) for use in hot mix asphalt (HMA) moisture sensitivity evaluation. In this paper, suggestions are presented to improve and provide more consistent and representative results for this test as described in AASHTO T 324 – Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA). In the AASHTO T 324 specification, either a cylindrical or a slab specimen can be tested. Use of a two-dimensional micromechanics finite element (2D-MMFE) analysis has demonstrated significant gap/bonding and specimen shape effects on HWTD test results for the cylindrical specimen setup. In addition, the analysis suggests the best method for defining the “rut depth” to ensure consistent results between two specimen setups. Results of this study have concluded that: (1) slab specimens can provide more reliable test results due to larger size and uniform geometry; (2) two cylindrical specimens (cores) should be glued together to prevent localized failure due to larger peak maximum principal strains when there is no bonding; (3) measurements of average rut depth should be collected from stations near the centers of cylindrical specimens to keep the specimen shape effects to the lowest possible level; and, (4) an agency should not allow both specimen setups to be used interchangeably in the HWTD specifications. The investigation also suggests that the average rut depth evolution curve fitted using a three-stage Weibull approach can define the number of passes to failure and define the stripping initiation point (SIP) better than the visually determined SIP.

Comments

Post a Comment

Popular posts from this blog

ATTERBERG LIMITS

ATTERBERG LIMITS The Atterberg limits are water contents which define the limits of various stages of consistency for fine-grained soils. The liquid limit (LL) and the plastic limit (PL) define the upper and lower limits, respectively, of the plastic range of a soil; the numerical difference between these two limits expresses the plasticity of a soil and is termed the plasticity index (PI). Liquid Limit The liquid limit of a soil is the water content, expressed as a percentage of the weight of oven-dried soil at which two halves of a soil pat separated by a groove of standard dimensions will close at the bottom of the groove along a distance of 1/2 in. under the impact of 25 blows in a standard liquid limit device. Plastic Limit The plastic limit of a soil is the water content, expressed as a percentage of the weight of oven dried soil at which the soil just begins to crumble into short pieces when rolled into a thread 1/8 in.  in diameter. P...
Read more

SAND

SAND Sand is a natural product which is obtained as river sand, nalla sand and pit sand. However sea sand should not be used for the following reasons: 1. It contains salt and hence structure will remain damp. The mortar is affected by efflorenscence and blisters appear. 2. It contains shells and other organic matter, which decompose after some time, reducing the life of the mortar. Sand may be obtained artificially by crushing hard stones. Usually artificial sand is obtained as a by-product while crushing stones to get jelly (coarse aggregate). Sand is used in mortar and concrete for the following purpose: 1. It sub-divides the paste of binding material into thin films and allows it to adhere and spread. 2. It fills up the gap between the building blocks and spreads the binding material. 3. It adds to the density of the mortar. 4. It prevents the shrinkage of the cementing material. 5. It allows carbon dioxide from the atmosphere to reach some depth and thereby improve...
Read more