oa Journal of Construction Project Management and Innovation - Assessing the impact of delays on the productivity of concrete placement by cranes in Nigeria
Infrastructural construction investment in Nigeria is currently estimated at US$5bn annually and of the key trades in the industry, concreting makes up about 15% of the total frequency of operations. One of the most dominant concrete-placement methods in Nigeria is by crane and skip and it has been established that fractional delay (delay time expressed as a fraction of pour duration) is the most significant factor affecting its productivity. This study therefore focused on evaluating the extent of delays on craned concrete placement in Nigeria and determining their effects on concreting productivity. The study involved a close observation of 35 daily concrete pours placed by crane and skip on 25 project sites selected through stratified random sampling procedure in Lagos. Productivity data obtained were analysed by multiple regression to obtain a model relating productivity to fractional delay. The results showed an average delay of above 23% of the pour time while the productivity is reduced by more than 2.5 m3/h for every 10% increase in delay. The latter is over 5 times the productivity reduction obtained in Hong Kong study for the same percentage increase in delay and confirms that delay has a far greater impact on the productivity of concrete placement by cranes in Nigeria than in other countries. It was recommended that serious, and concerted, managerial actions be directed at proper planning and scheduling of material deliveries as well as labour and equipment inputs by adopting the developed model to monitor and eliminate most delays and sustain productivity.
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