COMPARATIVE EVALUATION OF RECLAIMED ASPHALT (RA) AND LATERITE AS SUB-BASE MATERIALS FOR FLEXIBLE PAVEMENT CONSTRUCTION

T. Kassar, M.I. Bala, M. Tyogo

Abstract



The continued dependence on lateritic soil for sub-base construction in Nigeria has intensified borrow-pit quarrying, land degradation and the depletion of natural aggregate reserves, while large volumes of reclaimed asphalt (RA) generated during road rehabilitation remain underutilised. This study presents a comparative laboratory evaluation of RAP and laterite as sub-base materials for flexible pavements. RAP was obtained from milled stockpiles of the Keffi–Maraba Expressway expansion project, and laterite was sampled at a depth of 1.0 m from a borrow pit in the North Bank area of Makurdi, Benue State. Both materials were characterised through natural moisture content, particle-size distribution, Atterberg limits, modified Proctor compaction and California Bearing Ratio (CBR) tests under soaked and unsoaked conditions, in accordance with BS 1377 (1990), the relevant ASTM standards and the Federal Ministry of Works and Housing (FMWH, 1997) specification. One-way analysis of variance (ANOVA) with Levene’s test for homogeneity of variance was used to assess statistical significance. RAP recorded a very low natural moisture content of 1.65% against 56.38% for laterite (p < 0.001). Both materials were well-graded gravels (USCS “GW”; AASHTO A-1-a), with coefficients of uniformity of 23.7 (RAP) and 12.4 (laterite) and fines contents below 3%, and both compacted to a comparable maximum dry density of about 1.70 g/cm³ (RAP at ? 8% and laterite at ? 9% optimum moisture content; p = 0.859). Laterite was of medium plasticity (LL = 37%, PL = 12.9%, PI = 24.1%), whereas RAP was non-plastic. Laterite recorded higher CBR values (39% unsoaked, 33% soaked) than RAP (26% unsoaked, 21% soaked); the difference was statistically significant (F = 27.17, p < 0.002, ?² = 0.766). On soaked CBR, laterite satisfied the 30% minimum requirement for sub-base, while unbound RAP fell marginally short and would require blending with natural aggregate or chemical stabilisation to comply. RAP nevertheless offers superior moisture stability and substantial environmental benefits through waste diversion and aggregate conservation. The study concludes that RAP is a technically viable and environmentally sustainable sub-base alternative for low- to medium-traffic roads when appropriately processed, and recommends blended RAP–laterite or stabilised RAP systems for routine adoption.

KEYWORDS: Reclaimed asphalt pavement, Laterite, Sub-base, California Bearing Ratio, Compaction, Sustainable pavement, Geotechnical properties

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References


AASHTO. (2013). Standard specification for moisture–density relations of soils (T99/T180). American Association of State Highway and Transportation Officials.

Al-Qadi, I. L., Elseifi, M., & Carpenter, S. H. (2007). Reclaimed asphalt pavement — a literature review (FHWA-ICT-07-001). Illinois Center for Transportation.

Arulrajah, A., Disfani, M. M., & Horpibulsuk, S. (2011). Strength and stiffness of recycled pavement materials containing RAP. Journal of Materials in Civil Engineering, 23(11), 1512–1520.

Arulrajah, A., Disfani, M. M., & Horpibulsuk, S. (2012). Strength and deformability of recycled concrete aggregate mixtures stabilized with cement kiln dust. Journal of Materials in Civil Engineering, 24(2), 232–243.

Arulrajah, A., Piratheepan, J., Bo, M. W., & Disfani, M. M. (2013). Geotechnical properties of recycled construction and demolition materials and recycled asphalt pavement as base/sub-base materials. Construction and Building Materials, 47, 273–280.

Bell, F. G. (1996). Engineering properties of soils and rocks (4th ed.). Blackwell Science.

British Standards Institution. (1990). BS 1377: Methods of test for soils for civil engineering purposes. London: BSI.

Copeland, A. (2011). Reclaimed asphalt pavement in asphalt mixtures: State of the practice (FHWA-HRT-11-021). Federal Highway Administration.

Craig, R. F. (2004). Soil mechanics (7th ed.). Spon Press.

Das, B. M. (2016). Principles of geotechnical engineering (9th ed.). Cengage Learning.

Federal Highway Administration. (2016). User guidelines for waste and byproduct materials in pavement construction. FHWA.

Federal Ministry of Works and Housing (FMWH). (1997). General specification for roads and bridges (Vol. II). Lagos: FMWH.

Gidigasu, M. D. (1976). Laterite soil engineering: Pedogenesis and engineering principles. Elsevier.

Holtz, R. D., & Kovacs, W. D. (1981). An introduction to geotechnical engineering. Prentice Hall.

Hossain, M., Masad, E., & Pan, T. (2011). Laboratory evaluation of reclaimed asphalt pavement materials for unbound applications. Construction and Building Materials, 25(5), 2291–2297.

Little, D. N. (2004). Recycling of asphalt pavements. Public Roads, 68(1), 27–32.

Molenaar, A. A. A., & van Niekerk, A. A. (2002). Effects of gradation, composition and degree of compaction on the mechanical characteristics of recycled asphalt mixtures. Materials and Structures, 35(3), 160–166.

Murthy, V. N. S. (2002). Soil mechanics and foundation engineering. New Delhi: UBS Publishers.

Nelson, J. D., & Miller, D. J. (1992). Expansive soils: Problems and practice in foundation and pavement engineering. Wiley.

Nwaiwu, C. M. O., & Uzodinma, F. C. (2020). Suitability assessment of selected lateritic soils for highway construction in Anambra State, Nigeria. FUOYE Journal of Engineering & Technology, 5(2).

O’Flaherty, C. A. (2002). Highway engineering (3rd ed.). London: Thomas Telford.

Ola, S. A. (1978). Laterite in engineering construction in Nigeria. Journal of the Nigerian Institute of Engineers, 12(3), 25–34.

Olanipekun, E. A., & Abegunde, A. O. (2015). Comparative assessment of reclaimed asphalt pavement and natural aggregates for sub-base layers. International Journal of Pavement Engineering, 16(7), 601–609.

Oloruntoba, E. O. (2020). Effect of recycled pavement materials on sub-base performance. Nigerian Journal of Civil Engineering, 18(1), 87–99.

Osinubi, K. J., & Nwaiwu, C. M. (2006). Compaction and CBR characteristics of lateritic soils stabilized with cement and lime. Journal of Engineering and Applied Sciences, 1(1), 12–18.

Poon, C. S., & Chan, D. (2006). Feasible use of recycled concrete aggregates and crushed clay brick as unbound road sub-base. Construction and Building Materials, 20(8), 578–585.

Tam, V. W. Y., & Tam, C. M. (2006). Assessment of the re-use of demolition waste in Hong Kong. Resources, Conservation and Recycling, 47(3), 157–172.

Terzaghi, K., Peck, R. B., & Mesri, G. (1996). Soil mechanics in engineering practice (3rd ed.). Wiley.

Witczak, M. W., & Tia, M. (2015). Asphalt mixture design and testing. CRC Press.

Zhang, L., Chen, H., & Xu, X. (2015). Performance evaluation of RAP-blended sub-base materials for road construction. Journal of Materials in Civil Engineering, 27(9), 04015034.


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