Hot Rolled Asphalt Research Articles

EVALUATION OF ASPHALT FATIGUE PROPERTIES IN THE LABORATORY.

Three-point flexural fatigue tests have been carried out on prismatic specimens cut from laboratory manufactured slabs of five asphaltic materials including a hot rolled asphalt, a dense bitumen macadam and a stone mastic asphalt. Identical slabs of these materials were made to produce cylindrical specimens which were tested in the diametral fatigue test, called in the UK the indirect tensile fatigue test (ITFT). A detailed derivation is presented of the theory used to establish the feasibility of the ITFT as a fatigue test for asphaltic materials. The test results show that, at low strain levels, the fatigue lines of the five mixtures from the ITFT assume similar relative positions to those from flexural tests. However, for the same strain level, the fatigue lives measured in the ITFT are considerably shorter for all the mixtures tested. The paper highlights some of the concerns observed in connection with the ITFT procedure and their implications for fatigue testing practice.

The combined effects of porous asphalt surfacing and barriers on traffic noise

There is considerable interest in the use of porous asphalt (PA) surfacing on highways since physical and subjective assessments of noise have indicated a significant advantage over conventional non-porous surfaces such as hot rolled asphalt (HRA) used widely for motorway surfacing in the UK. However, it was not known whether the benefit of the PA surface was affected by the presence of roadside barriers. Noise predictions have been made using the Boundary Element Method (BEM) approach to determine the extent to which the noise reducing benefits of PA could be added to the screening effects of noise barriers in order to obtain the overall reduction in noise levels.

STONE MASTIC ASPHALT: ASSESSING THE EFFECT OF CELLULOSE FIBRE ADDITIVES.

Keywords ULSTER UNIVERSITY, AFYON UNIVERSITY ASPHALT, STONE, MASTIC, SMA, CELLULOSE, FIBRES, ADDITIVES, MIXTURES, SURFACING, BITUMINOUS, PERFORMANCE, CONTENT, GRADING, MIX, PROPERTIES, ROADS, HIGHWAYS, PAVEMENTS, DESIGN, STRENGTH, TESTS, TESTING, RESEARCH, LABORATORIES, MEASUREMENT, SPECIFICATIONS, STABILISATION, BINDERS, DRAINAGE, MARSHALL, STABILITY, CANTABRO, STIFFNESS, RESISTANCE, DEFORMATION... Show All

Microcomputer prediction of temperatures in the cooling of chipped hot rolled asphalt wearing course during laying

Bituminous pavement materials have low viscosity at elevated temperatures. This allows effective compaction during the laying process. In laying unchipped materials compaction is necessary to densify the mix whereas in laying chipped materials compaction is necessary to embed the chippings and also densify the matrix. Since wearing courses are normally 40 mm thick the time available for these aims to be met is limited. This time period is a function of the hot‐mix and underlying material properties and ambient parameters prevailing when it is laid.

Improvements to Pavement Subgrade Strain Criterion

Relationships between maximum allowable elastic strain on the subgrade and number of load repetitions have been used extensively in pavement design procedures. Their development is reviewed to allow a proper perspective on their correct use and as a background for describing improvements which take account of the differing deformation resistance offered by various asphalt mixtures. These improvements are derived from both field data and the results of an extensive testing program during the last four years at the University of Nottingham using repeated load triaxial tests. A continuously graded dense bitumen macadam base can carry more than 1‐1/2 times the number of load applications before developing the same limiting rut depth as a gap graded hot rolled asphalt of equal elastic stiffness. Factors on the design life against permanent deformation are given for four typical materials for use in conjunction with the subgrade strain criterion.

ASPHALT MIX CONTROL - A COMPUTER APPLICATION.

Keywords BRISTOL POLYTECHNIC ASPHALT, MIX, CONTROL, COMPUTERS, PROGRAMS, DESIGN, HOT ROLLED, HRA, MIXING, IMPLEMENTATION, MICROCOMPUTERS, PROPORTIONS, AGGREGATES, NUMERICAL, METHODS, AIRFIELDS, RESURFACING, LABORATORIES, SITES... Show All

One ear to the ground

This article briefly reviews the problem of road traffic noise and how to tackle it, then discusses some research on how thin surfacings can reduce tyre/surface noise. The generation of tyre/surface noise is complex, but the nature of the surface is especially important in the quantitative production of noise. Traditional wearing courses are typically 40-50mm thick, while thin surfacings are typically 20-30mm thick, with binder and aggregate laid as one layer. Although a thin surface layer contributes little to the strength of a road, it can reduce noise levels and restore skid resistance and riding quality. The A635 Doncaster to Barnsley main road in England has been paved with different thin surfaces at different sites: hot rolled asphalt (HRA), Masterpave (14mm), Hitex (14mm), stone mastic asphalt (SMA) (10mm), and safepave (10mm). Noise measurements were made at these sites and also on UL-M (10mm) surfaces on the B59 in Northern Ireland. Sound pressure levels were sampled at points 10m from the edge of the carriageway and 1.5m above the ground. On the A635, the measured average noise levels were 65.8dB(A) for Hitex, 66.0dB(A) for SMA, 67.5dB(A) for Masterpave, 68.1dB(A) for Safepave, and 69.9dB(A) for HRA; on the B59, they were 66.3dB(A) for UL-M and 69.1dB(A) for HRA.