Micromechanics of the Effects of Mixing Moisture on Foamed Asphalt Mix Properties
Publication: Journal of Materials in Civil Engineering
Volume 22, Issue 10
Abstract
The mixing moisture content (MMC) is an important mix design variable in pavement full-depth reclamation (FDR) with foamed asphalt. It has been known for many decades that MMC in the granular material subjected to foamed asphalt treatment can affect asphalt dispersion. This paper investigates the micromechanics of this phenomenon by combining direct microstructure observations and conventional laboratory testing. It was found that for a typical loose moist granular material with a considerable amount of fine particles, the agglomeration state evolves through a series of states as the MMC increases. If the MMC is high, the fine particles become saturated and form a pastelike substance that coats larger aggregate particles, creating large agglomerations with low surface area to volume ratios. Inferior asphalt dispersion is resulted for mixes in this state. Theories for wet agglomeration processes are used to explain the observations on the basis of thermodynamic equilibrium. Fracture face image analysis for tested indirect tensile strength specimens confirmed this observation. Laboratory tests also found that mixes with inferior asphalt dispersion due to suboptimal MMC yield low strength and low stiffness. These effects are particularly significant for granular materials with higher fines content. The main practical implication of the findings is that relatively dry loose granular mixes are preferred for foamed asphalt dispersion, and a balance should be sought between asphalt dispersion and mix compactability. The existing postulation that high MMC aids foamed asphalt dispersion is therefore dismissed.
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Acknowledgments
The work presented in this paper was sponsored by the California Department of Transportation, Division of Research and Innovation, for which the writers are grateful. The writers also wish to thank their collaborators in the California Department of Transportation, and at the UCPRC, especially Messrs. Syed A. Bukhari and You-Chen Chao, who provided valuable assistance with specimen preparation and testing. The results presented in this paper do not represent any standard or specification of the California Department of Transportation, and the opinions expressed are those of the writers alone. The support from the University of California, Davis Sustainable Transportation Center in the form of a dissertation fellowship awarded to the lead writer for the micromechanical analysis is also gratefully acknowledged.
References
Acott, S. M. (1980). “The stabilisation of a sand by foamed asphalt—A laboratory and field performance study.” MS thesis, Univ. of Natal, Pietermaritzburg, Natal, South Africa.
Asphalt Academy of South Africa. (2002). The design and use of foamed bitumen treated materials (interim technical guideline, TG2), Pretoria, South Africa.
Asphalt Institute. (1974). Mix design methods for asphalt concrete and other hot-mix types (MS-2), Lexington, Ky.
Brennen, M., Tia, M., Altschaefl, A., and Wood, L. E. (1983). “Laboratory investigation of the use of foamed bitumen for recycled bituminous pavements.” Transp. Res. Rec., 911, 80–87.
Castedo, F. L. H., and Wood, L. E. (1982). “Stabilization with foamed asphalt of aggregates commonly used in low-volume road.” Transp. Res. Rec., 898, 297–302.
Csanyi, L. H. (1960). “Bituminous mixes prepared with foamed asphalt.” Iowa Engineering Experiment Station bulletin no. 19, Iowa State University, Ames, Iowa.
Efrem, G. E. (2000). “Stabilisation of cinder with foamed bitumen and cement and its use as (sub)base for roads.” MS thesis, International Institute for Infrastructural, Hydraulic and Environmental Engineering, Delft, The Netherlands.
Fredlund, D. G., and Rahardjo, H. (1993). Soil mechanics for unsaturated soils, Wiley, New York.
Fu, P., Harvey, J. T., Jones, D. J., and Chao, Y. -C. (2008a). “Understanding internal structure characteristics of foamed asphalt mixes with fracture face image analyses.” Transp. Res. Rec., 2057, 20–27.
Fu, P., Jones, D., Harvey, J. T., and Bukhari, S. A. (2008b). “Dry and soaked laboratory tests for foamed asphalt mixes.” J. Assoc. Asph. Paving Technol., 77, 71–106.
Fu, P., Jones, D., Harvey, J. T., and Bukhari, S. A. (2009). “Laboratory testing methods for foamed asphalt mix resilient modulus.” Road Mater. Pavement Des., 10(1), 187–212.
Fu, P., Jones, D., Harvey, J. T., and Halles, F. A. (2010). “An investigation of the curing mechanism of foamed asphalt mixes based on micromechanics.” J. Mater. Civ. Eng., 22(1), 29–38.
Jenkins, K. J. (2000). “Mix design considerations for cold and half-cold bituminous mixes with emphasis on foamed bitumen.” Ph.D. thesis, Univ. of Stellenbosch, Stellenbosch, Western Cape, South Africa.
Jones, D., Fu, P., Harvey, J. T., and Halles, F. A. (2008). “Full-depth recycling with foamed asphalt: Final report.” Research Rep. No. UCPRC-RR-2008-07, Univ. of California Pavement Research Center, Davis and Berkeley, Calif.
Kim, Y., and Lee, H. D. (2006). “Development of mix design procedure for cold in-place recycling with foamed asphalt.” J. Mater. Civ. Eng., 18(1), 116–124.
Lee, D. Y. (1981). “Testing marginal aggregates and soils with foamed asphalt.” Electron. J. Assoc. Asph. Paving Technol., 50, 211–250.
Little, D. N., Button, J. W., and Epps, J. A. (1983). “Structural properties of laboratory mixtures containing foamed asphalt and marginal aggregates.” Transp. Res. Rec., 911, 104–113.
Lu, N., and Likos, W. J. (2004). Unsaturated soil mechanics, Wiley, New York.
Mehrotra, V. P., and Sastry, K. V. S. (1980). “Pendular bond strength between unequal sized spherical particles.” Powder Technol., 25, 203–214.
Newitt, D. M., and Conway-Jones, J. M. (1958). “A contribution to the theory and practice of granulation.” Trans. Inst. Chem. Eng., 36, 422–441.
Proctor, R. R. (1933). “Fundamental principles of soil compaction.” Eng. News-Rec., 111, 245–248, 286–289, and 348–351.
Roberts, F. L., Engelbrecht, J. C., and Kennedy, T. W. (1984). “Evaluation of recycled mixtures using foamed asphalt.” Transp. Res. Rec., 968, 78–85.
Ruckel, P. J., Acott, S. M., and Bowering, R. H. (1983). “Foamed-asphalt paving mixtures: Preparation of design mixes and treatment of test specimens.” Transp. Res. Rec., 911, 88–95.
Sakr, H. A., and Manke, P. G. (1985). “Innovations in Oklahoma foam mix design procedures.” Transp. Res. Rec., 1034, 26–34.
Saleh, M. F. (2004). “New Zealand experience with foam bitumen stabilization.” Transp. Res. Rec., 1868, 40–49.
Seed, H. B., and Chan, C. K. (1959). “Structure and strength characteristics of compacted clays.” J. Soil Mech. and Found. Div., 85(5), 87–128.
Uzan, J. (1985). “Characterization of granular material.” Transp. Res. Rec., 1022, 52–59.
Wirtgen GmbH. (2004). Wirtgen cold recycling manual, Windhagen, Germany.
Information & Authors
Information
Published In
Journal of Materials in Civil Engineering
Volume 22 • Issue 10 • October 2010
Pages: 985 - 995
Copyright
© 2010 ASCE.
History
Received: Apr 17, 2009
Accepted: Mar 6, 2010
Published online: Mar 16, 2010
Published in print: Oct 2010
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