Some Geological Considerations and Durability Analysis on the Use of Crushed Pyroclastics from Abakaliki (Southeastern N
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ORIGINAL PAPER
Some Geological Considerations and Durability Analysis on the Use of Crushed Pyroclastics from Abakaliki (Southeastern Nigeria) as Concrete Aggregate O. P. Aghamelu • C. O. Okogbue
Received: 1 August 2012 / Accepted: 30 January 2013 / Published online: 6 February 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract Samples of pyroclastic rocks from Abakaliki area (Nigeria) were subjected to geological and geochemical tests to determine the suitability and durability of the rocks as concrete aggregate. Petrographic analysis shows fine-grained texture and predominance of plagioclase (21–60 %) and shaley-muddy lithic fragment, while geochemical analysis classifies the rocks as alkaline. Analysis indicates that the pyroclastics would likely perform marginally well as concrete aggregates, especially in heavy Portland cement concrete and bituminous concrete. This is due to appreciably high values of natural moisture content, low bulk density, relative density and specific gravity, which suggests low durability, high voids and less aggregate absorption in concrete and bitumen mixes. The rocks are rated as moderate to high strength material on the basis of their unconfined compressive strength values, but are very likely to have low durability as buttressed by poor sulphate soundness test results, probably due to high amount of weak minerals. Analyses reveal that the Abakaliki Pyroclastics are not completely satisfactory as
O. P. Aghamelu (&) Department of Geology and Exploration Geophysics, Ebonyi State University, P.M.B., 053, Abakaliki, Nigeria e-mail: [email protected] C. O. Okogbue Department of Geology, University of Nigeria, Nsukka, Nigeria e-mail: [email protected]
concrete aggregates source, despite their origin, texture, strength and economic availability. Hence, caution is required when they are used in concrete projects. Keywords Petrography Concrete Pyroclastics Performance Nigeria
1 Introduction One of the important factors that influence quarrying and utilization of rocks in construction is their economic availability. In the Abakaliki area (Fig. 1), pyroclastic rocks are found associated with thick Albian Asu River Group sediments. The occurrence and petrology of these rocks commonly referred to as the ‘Abakaliki Pyroclastics’ (a name first used by Okezie 1965) have been extensively studied by earlier researchers such as Farrington (1952), Uzuakpunwa (1974) and Olade (1979). Due to the abundance of this type of rocks in the area, commercial and mechanized quarrying activity is currently being carried out by a conglomeration of stone crushers at the Stone Crushers Enterprise Zone, Umuoghara (a stone crushers’ cluster mapped out by the Government of Ebonyi State in the outskirt of the Abakaliki Metropolis). There, about 10,000 metric tonnes of crushed varieties of mainly pyroclastics are produced on a daily basis. These products are being used in most construction
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Geotech Geol Eng (2013) 31:699–711
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