01155683

Component

This study investigated the effects of asphalt binder foamability and granular material fines content on foamed asphalt mix strength behavior. The laboratory testing program used a full experiment factorial consisting of two pulverized asphalt pavement (PAP) sources, six constituted fines contents, and three asphalt binders, one of which was foamed using two different foaming parameters. In total, 1,152 indirect tension strength (ITS) specimens were fabricated and tested. The test results showed that asphalt binders with better foaming attributes (higher expansion ratios and longer half-lives) tend to yield mixes with higher strength, as expected. For the same asphalt binder, a small change in foaming parameters (asphalt temperature and foamant water ratio) can significantly alter the expansion ratio and half-life. However, this usually has only a minimal effect on the mix properties. This implies that in project level mix design, more attention should be paid to identifying available asphalts with better foaming characteristics rather than trying to find the “best” foaming parameters for an asphalt type. In terms of the effects of fines content, strength consistently decreased as fines content increased at each asphalt content level, for both PAP sources. When the fines content increases, a larger proportion of these fines are not bonded with the available foamed asphalt. The absolute volume of asphalt mastic (mixture of asphalt and fines) produced might be increased, but the mineral filler phase (fines not bonded by asphalt) occupies relatively more space in the mix, yielding lower strength. Therefore introducing excessive fines, especially to the extent that the fines content is higher than 12 percent is detrimental to foamed asphalt mix performance and strongly discouraged in engineering practice.

01147878

10-2968

English

13p

2010

Transportation Research Board 89th Annual Meeting

DVD

Figures (3) ; References (16) ; Tables (2)

Asphalt mixtures; Asphalt pavements; Binders; Bituminous materials; Fillers (Materials); Foamed asphalt; Full-depth reclamation; Mix design; Strength of materials

Highways; Materials; Pavements; I32: Concrete; I52: Construction of Pavements and Surfacings

Transportation Research Board Annual Meeting 2010 Paper #10-2968

TRIS, TRB

Jan 25 2010 11:27AM