Studying Construction Site Wastes Based on Lean Thinking on Selected Addis Ababa Building Construction Sites: A Case Study

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In recent years waste in the construction industry has been the subject of several research projects around the world. Researchers implement different methods to reduce the amount of waste in construction industry. One of the effective methods is application of lean approach to construction industry. Lean construction is a result of the introduction of a new form of production management. Although lean construction is still evolving, the generic principles, techniques and tools of lean construction can already be applied. Waste reduction in order to improve performance is one of the basic concepts of lean thinking. In general, project managers tend to conceptualize “waste” as physical construction waste, but there are noticeable wastes in the construction processes which are named “non -value adding activities (NVA)” by lean construction theory. In addition to stressing on the physical waste, lean thinking specifically pay lots of attentions to the waste produced over a construction process. Waiting time, non -value adding works and material transportations are categorized in this group. This research is based on studying construction site wastes based on lean construction concept on selected Addis Ababa construction sites. At first three major activities were selected (rebar work, concrete work and column work) then two case studies were conducted for each of the selected activities to identify and categorize each workers activity in a crew member based on lean concept of waste, afterward the case studies are compared. In general six case studies at six construction sites were conducted. In addition questionnaires were distributed among project managers on construction sites where the case studies were led in order to perceive full understand on how they comprehend construction wastes. After analyzing all the collected data conclusions and recommendations were made based on the analyzed facts. The key finding of this research is that in almost all case studies conducted, working times spent on non-value adding activities took considerable amount of time. In addition among the non-value adding activities waiting time overcomes taking the biggest share in almost all case studies, this refers to an interruption of flow in the work process due to various reasons, like late delivery of materials, tools and equipment to construction sites, moreover waiting times indicates excessive allocation of workers which led to unproductive working hours (doing noting).In addition case studies result shows that using better technologies (machineries and materials) contributed to less waiting time, less unnecessary transportation of materials by workers, less defect and reworks on construction sites. Also analyzed facts showed that wastes that arise out of unnecessary stock of construction materials (inventory) can possibly be avoided by having separate workshops, using ready mix concrete and modular elements. In addition time spent on non- value adding but required activities like temporary work and supporting activities (formwork) can also be minimized by using better technologies( materials and equipment), plus associated NVA activities like waiting time, defective work and re-works can also be avoided. This research also showed that construction wastes are seen as only physical wastes (material wastes) by the companies where the case studies were conducted.



Construction waste, Lean construction, Lean thinking, Lean principles, Value adding (VA), Non -value adding (NVA), Non -value adding but required (NVAR)