ASPHALT ROAD DETERIORATION ASSOCIATED WITH MINERALOGY OF ROCK AGGREGATES A PETROGRAPHICAL STUDY

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Box 237, Tarkwa, Ghana) ABSTRACT This paper assessed the petrographic changes in road construction aggregates and their contributions to road deterioration at Tarkwa using thin section examination of

1 ASPHALT ROAD DETERIORATION ASSOCIATED WITH MINERALOGY OF ROCK AGGREGATES A PETROGRAPHICAL STUDY George M. Tetteh1, Derry S. Alakuu1 1 (Department of Geological Engineering, University of Mines and Technology, P. O. Box 237, Tarkwa, Ghana) ABSTRACT This paper assessed the petrographic changes in road construction aggregates and their contributions to road deterioration at Tarkwa using thin section examination of deteriorated asphalt road samples taken from the pavement, infill and concrete parts. The rock aggregates contain plagioclase partially altered to sericite, and amphibole partially altered to chlorite. Deterioration of the road was enhanced as bitumen, the binding medium, was attacked by sericite and chlorite which, however, had no effect on cement, the binding medium for the concrete. Therefore concrete is recommended for road construction in the area. Keywords:Asphalt road, Aggregates, Road deterioration, Bitumen, Cement, Sericite, orite 1 INTRODUCTION Earth materials used for road construction include rock aggregates (sand, gravel and soil). These materials are used mainly as subgrade and sub-base (Jim, 1999). Pavement materials used in road construction are unbound granular materials usually crushed stone, crushed slag or concrete, or slate mixed with bitumen or cement for the top layer of roads (Anon., 2013). Sharad and Gupta (2004) identified causes of road deterioration as due to the subgrade or the sub-base material, the degree of compaction on the subgrade or sub-base material, sudden increase in traffic load, temperature variation, poor shoulders leading to edge failures, poor drainage conditions, improper maintenance of the temperature of bituminous mixture and mineralogical composition of materials. There have been some petrographic assessments of construction aggregates (Brag and Foster, 1994). Research on roads have not evaluated petrographic changes in the used aggregates. This paper assessed the petrographic changes of road construction materials after rapid road deterioration at Tarkwa - a road that links AgonaNkwanta to the south (Fig. 1). Tarkwa is the capital of Tarkwa-Nsuaem Municipality in the Western Region of Ghana. The Tarkwa-Nsuaem Municipality is accessible by truck road and railway. The major road networks in the municipality links major towns such as Takoradi and Kumasi. The municipality is also connected by rail to Takoradi and Kumasi (Anon., 2006). a) b) Fig. 1 a) Geological Map of south western Ghana (After, Leubeet al., 1990) b) Map of Western Region of Ghana showing the study area on the Tarkwa-AgonaNkwanta Road 572

2 Tarkwa and its environs generally lie within mountain ranges covered by thick forest with a variety of fauna and flora. In some cases, the ranges are interspersed by undulating valleys. The hills rise to an average height of 300 m above sea level and reach 335 m. The mountain ranges are rich in biodiversity, particularly before the onset of mining and numerous settlements (Akabzaa and Darimani, 2001).The Tarkwa region is also part of an extensive drainage basin known as the Ankobra Basin comprising the Ankobra River and its local tributaries - Bonsa sub-basin containing the Bonsa River and its tributaries such as Essumang, Angonabeng and AhumAbru. River Bonsa takes its source from the ridges within the mining concessions of large-scale mining companies operating open pit mines and so the water is illegally used for gold ore processing by artisanal mines locally known as galamsey (Akabzaa and Darimani, 2001). The area falls within the equatorial climatic zone, primarily the tropical rainforest zone of Ghana. The district has a mean annual rainfall in the range of 1500 mm and 1933 mm with most rainfall occurring from April to June and October to November giving it a bi-modal rainfall pattern. Relative humidity for the area ranges from 70 % to 90 %. Daily temperature ranges between 20 C and 40 C while the mean monthly temperature ranges from 24 C to 30 C (Akabzaa and Darimani, 2001). The geological formations in the municipality are mostly the Birimian and Tarkwaian rocks. Tarkwa is located on the contact between the Tarkwaian rocks at the west and older Birimian Supergroupto the east (Eisenlohr and Hirdes, 1992). The Tarkwaian Group is made up of a sequence of clastic sedimentary rocks, which comprises of sandstones, conglomerates and phyllites. It is spatially associated with belt volcanic rocks and granitoids of the Birimian. The Tarkwaian is regarded as sourcedfrom the Birimian rocks that were uplifted and eroded in the Eburnean event. The rocks of the Tarkwaian consist of the Kawere Group, Banket Series, Tarkwa Phyllite and Huni Sandstone. The Kawere Group is the oldest group, and the conglomerates consist of silicified Birimian greenstone and hornstone with minor jasper, quartz, quartz-porphyry, tourmaline-quartz rocks with Birimian phyllites and schists in a matrix made up of quartz, feldspar, chlorite, carbonate, epidote and magnetite. The Banket conglomerate consists of 90 % quartz, and the rest are Birimian schist, quartzite, hornstone, chert and gondite. The Tarkwa phyllitecomprises also ofchloritoid, magnetite or hematite with sericite and chlorite. Huni Sandstone consists of variable amounts of feldspar, sericite, chlorite, ferriferous carbonate, magnetite or haematite and epidote (Junneret al., 1942; Kesse, 1985). Trunk roads in the municipality undergo rapid deterioration due mainly to constant usage by heavy duty mine machines and heavy rainfall. Moreover, the abandoned railway system in the municipality has also contributed to the deterioration of the roads as there is increased traffic. Construction aggregates are defined as hard, granular materials which are suitable for use either on their own or with the addition of cement, lime or a bituminous binder (Harrison and Bloodworth, 1994). Natural road construction aggregates come in two main categories: as a hard rock aggregate obtained from igneous rocks such as granite, dolerite and gabbro, sedimentary rocks such as sandstone and limestone, and metamorphic rocks such as gneiss and marble; and the second category made up of sand and gravel. The surface course of roads (the uppermost part), is made up of a mixture of various selected aggregates bound together with asphalt, cement or bitumen. The base course forms the second layer from the surface of a road, which serves as the principal structural component of the flexible pavement. The materials used are hard and durable granular aggregates (Anon., 2016). Petrographically, an estimation of the rock geotechnical properties was studied for the intrinsic properties such as mineralogical composition, grain size and shape, micro-cracks (Lindqvistet al., 2007). Study of free mica properties and their influence on the quality of road constructions showed that high amount of free mica in aggregates have a negative influence on the quality of both bound and unbound applications, e.g. asphalt mass and aggregates for unbound applications (Dmitry, 2008). However, free mica-water interaction has been identified as one of the critical parameters for structural deterioration as accumulated water in mica-rich aggregates is the main reason for road heaving, rutting and reduction of bearing capacity during seasonal climate variation (Uthuset al., 2006: Miskovsky, 2003). Uthus (2007) further observed that some minerals interact with water, either by chemical bonding or by chemical reaction (swelling) and may have frost susceptibility and sensitivity to water e.g. mica. Elevated fractions of free mica particles in unbound granular materials, used in road constructions, are believed to reduce bearing capacity and influence the hydraulic behaviour of the road structure and in combination with water results in deterioration of resilient modulus (Ekblad, 2007). Significant deterioration of the mechanical properties of asphalt mass result with increased content of free mica in fine fractions (Miskovsky, 2004). Bragg (1998) advised that for a material to be used as construction aggregate, it should initially be rated by the number of deleterious substances as these contain features that are capable of causing adverse effects, resulting in premature deterioration of the rock, asphalt or cement used in concrete. 573

2 METHODS USED Broken parts removed during road work in front of the University of Mines and Technology (UMaT) gate were cleaned with water to ensure clear observations (Fig. 2).

3 2 METHODS USED Broken parts removed during road work in front of the University of Mines and Technology (UMaT) gate were cleaned with water to ensure clear observations (Fig. 2). Hand specimen description was conducted using hand lens of magnification 20. Fig. 2 Photograph of a Section of Deteriorated road at Tarkwa Other samples were collected randomly from broken parts of the pavementopposite University of Mines and Technology main gate, packaged in sample bags and labelled. Concrete samples were taken from a broken tunnel near Ransbet Super Market. An infill rock fragment was also taken in front of the Kamponase community (Camp City), opposite the University. Thin section preparation was conducted at the petrological laboratory at University of Mines and Technology, Tarkwa with modal percentage estimated by point counting. 2.1 Petrography Pavement material In hand specimen, the pavement material is principally composed of quartz, granitoid with bitumen as the binding material. The primary component is quartz, moderate granitoid fragments with the least being bitumen. In thin section, plagioclase in the granitoid aggregate is partially altered to sericite, and amphibole also partially altered to chlorite (Fig. 3) (Table 1) Concrete material In hand specimen, the concrete sample is composed of tourmaline, macro-granite, greywacke, quartzite and feldspar porphyry granitoid, all bound in cement matrix (Table 1). In thin section, hair or irregular fractures and alteration products of sericite and chlorite occur (Fig. 4) Infill material In hand specimen, the infill sample is composed mainly of feldspar, moderate manganese carbonate and opaque minerals, with minor quartz and granitoid (Table 1). In thin section, plagioclase and amphibole are also highly altered to sericite and chlorite respectively (Fig. 5). 574

Table 1 Composition of Aggregates and Minerals in Samples Material Minerals/Rocks Pavement Concrete Infill Tourmaline 8 Quartz 50 10 Greywacke 8 Feldspar 40 35 Opaque 25 Manganese carbonate 25

4 Table 1 Composition of Aggregates and Minerals in Samples Material Minerals/Rocks Pavement Concrete Infill Tourmaline 8 Quartz Greywacke 8 Feldspar Opaque 25 Manganese carbonate 25 fragment Macro-granitoid 15 fragment Granitoid fragment 20 5 Quartzite fragment 5 Cement matrix 24 Bitumen matrix Total Fig. 3 Photomicrograph of Pavement Sample under Plane Polarised Light showing: (a) partially altered plagioclase to Sericite, and partiallyaltered amphibole to orite (b) Sericite and chlorite attack on bitumen 575

$4 Photomicrograph of Concrete Sample showing (a) Concrete mixture with hair or irregular fractures, under$ $Plane Polarised Light (b) Hair or irregular fractures in Concrete Sample, under Cross Nicols A B Bitumen$ amphibole to chlorite with patchy quartz and disseminated sulphides and low carbonate rock fragment (a)

amphibole to chlorite with patchy quartz and disseminated sulphides and low carbonate rock fragment (a)

road that links Sekondi-Takoradi to Bogoso, a distance of about 61.2 km.

5 B A Fig. 4 Photomicrograph of Concrete Sample showing (a) Concrete mixture with hair or irregular fractures, under Plane Polarised Light (b) Hair or irregular fractures in Concrete Sample, under Cross Nicols A B Bitumen Ser Ser 2mm Fig 5 Photomicrograph of Infill Sample showing plagioclase highly altered to sericite and amphibole to chlorite with patchy quartz and disseminated sulphides and low carbonate rock fragment (a) under Plane Polarised Light (b) under Cross Nicols 3 DISCUSSION Tarkwa-AgonaNkwanta road is a class one road that links Sekondi-Takoradi to Bogoso, a distance of about 61.2 km. Natural aggregates used in its construction are mainly granitoid, Nsuta manganese carbonate-bearing greenstone, sand and gravel (Anon., 2017). Sericite and chlorite were products of alteration in the rock aggregates as plagioclase was partially 576

6 altered to sericite and quartz, and amphibole is partially altered to chlorite (Fig. 5a). The infill rock sample was highly altered (Fig. 5). Deterioration of the road was enhanced as bitumen; the binding medium was attacked by sericite and chlorite (Fig. 4b). These alteration minerals led to rapid deterioration of the asphalt portion of the road. However, the concrete material depicted irregular hair fractures due to fatigue or load from heavy duty trucks as there was no attack of cement, the binding medium, by sericite and chlorite (Fig. 5). Miskovsky (2004) observed that sericite and chlorite have the ability to absorb bitumen to produce weak zonesin asphalt leading to road heaving, rutting and reduction of bearing capacity. 4 CONCLUSIONS Plagioclase and amphibole in rock aggregates used in the construction of the Tarkwa road are partially altered to sericite and chlorite respectively. These alteration products attached bitumen to speed up asphalt road deterioration. Hence, aggregates low in altered plagioclase and amphibole should be used in road construction with bitumen in the area. Otherwise, concrete paved roads should be constructed. REFERENCES 1. Akabzaa, T. and Darimani, A. (2001), Impact of Mining Sector Investment in Ghana, A Study of the Tarkwa Mining Region, 52pp. 2. Anon. (2006), Tarkwa Nsuaem Municipal Assembly, Accessed: March 10, Anon. (2013), Construction Aggregates, Mineral Planning Factsheet, British Geological Survey, Natural Environment Research Council, 31 pp. 4. Anon. (2016) Composition and Structure of Flexible Pavements, andxsstructure/5499. Accessed: March 9, Anon. (2017), Roads, March 9, Brag, D. J. and Foster, K. (1994), Petrographic Analysis of Coarse Aggregates, Journal of Ministry of Transportation Ontario, Vol. 91, No. 256, pp Bragg, D. J. (1998), Petrographic Examination of Construction Aggregates of Newfoundland Current Research Newfoundland Department of Natural Resources, Geological Survey, Report (95.1), pp Dmitry, K. (2008), Studies of the Free Mica Properties and its Influence on the Quality of Road Construction, Published Thesis, University of Ulster, England, 26 pp. 9. Eisenlohr, B. N. and Hirdes, W. (1992), The Structural Development of the Early Proterozoic Birimian and Tarkwaian Rocks of South West Ghana, West Africa, Journal of African EarthSciences, Vol. 14, No. 3, pp Ekblad, J. (2007), Influence of Water on Coarse Granular Road Material Properties, Published PhD Thesis, KTH Royal Institute of Technology, Stockholm, 121 pp. 11. Harrison, D. J. and Bloodworth, A. J. (1994), Industrial Minerals Laboratory Manual: Construction Materials. Technical Report of British Geological Survey, Vol. 1, No. 2, pp Jim, G. (1999), Pavements and Surface Materials, Nonpoint Education Technical Paper for Municipal Officials, Vol. 1, No. 8, pp Junner, N. R., Hirst, T. and Service, H. (1942), The Tarkwa Goldfield. Gold Coast Geological Survey, Memoir, Vol. 6, No. 3, pp Kesse, G. O. (1985), The Mineral and Rock Resources of Ghana, A. A. Balkema Publishers, Rotterdam, 610 pp. 15. Leube, A., Hirdes, W., Mauer, R., and Kesse, G. (1990). The early Proterozoic Birimian Supergroup of Ghana and some aspects of its associated gold mineralisation, PrecambrianResearch, Vol. 46, pp Lindqvist, J. E., Akesson, U. and Malaga, K. (2007), Microstructure and Functional Properties of Rock Material, Journal of Material Characterisation, Vol. 5, No.11, pp Miskovsky, K. (2003), Influence of the Mineralogical Composition and Textural Properties on the Quality of Course Aggregates, Journal of Materials Engineering and Performance, Vol.13, No.5, pp Miskovsky, K. (2004), Enrichment of Mica from Rock Aggregate Production and its Influence on the Mechanical Properties of Bituminous Mixtures, Journal of Materials Engineering and Performance, Vol. 13, No. 1, pp

7 19. Sharad, S. A. and Gupta, A. K. (2004), Pavement Deterioration and its Causes, Journal of Mechanical and Civil Engineering, Vol. 5, No. 1, pp Uthus, L., Hermansson, Å. Horvli, I. and Hoff, I. (2006), A study on the influence of water and fines on the deformation properties and frost heave of unbound aggregates, Proceedings of the 13th International Conference on Cold Regions Engineering, Orono, Maine. 21. Uthus, L. (2007), Deformation Properties of Unbound Granular Aggregates, PhD Thesis submitted to the Department of Civil and Transport Engineering, Faculty of Engineering Science and Technology, the Norwegian University of Science, Trondheim, 12 pp. 578

Assessment of Cracks on a Building at Tarkwa in Ghana with Respect to Foliations and Joints in Foundation Tarkwaian Rocks

International Journal of Mining Science (IJMS) Volume 2, Issue 1, 2016, PP 25-32 ISSN 2454-9460 (Online) www.arcjournals.org Assessment of Cracks on a Building at Tarkwa in Ghana with Respect to Foliations