Road construction engineering in Nigeria


American countries have started to look for new ways of contracting out road maintenance. With technical assistance from the International Road Federation and German Aid, Colombia, Brazil, Guatemala, Peru and Uruguay have initiated so called Performance Specified Road Maintenance Contracts on a pilot basis. In addition, Argentina and Chile have let several such contracts recently. In this scheme the Road Authority serves as the owner, but out-sources both the management and production of the maintenance work to a single contractor. Most of these contracts have been operating for more than a year and cover routine maintenance and, in some cases, periodic maintenance and road rehabilitation as well. Extension of the road network, road surfaces and conditions, and the time period vary in each pilot project and will provide a wide basis for evaluation and improvements.

A total of 15 samples from the Abakaliki pyroclastic rock bodies were subjected to petrographic and mechanical analyses to determine the suitability of the rock type as a road aggregate. Results indicate that the Abakaliki pyroclastic rock yield aggregates with marginal performance in road projects. Although the aggregates meet a number of road stone requirements (i.e., ten percent fines and their ability to absorb water), they fail to meet other key road stone requirements. Whilst their aggregate impact values, Los Angeles abrasion values, and flakiness index are generally above the recommended limits, petrographic analyses reveal appreciable amounts of shaley to muddy lithic fragment and volcanic glassy groundmass. These detrimental constituents and marginal laboratory test results would likely translate to long term poor field performance where the pyroclastic aggregate is used for road construction. This study suggests that utilization of the Abakaliki pyroclastic rock as an aggregate, especially for road construction, requires informed caution, particularly when the material is exposed to climatic extremes (high volume of rainfall and high and fluctuating temperature) as is the case in the tropics.



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