Cost and Time Impacts of Reworks in Building a Reinforced Concrete Structure

ABSTRACT: In construction industry, rework is one of the major factors that affect the success of a construction project. It causes to decrease the quality and productivity, and increases the cost and time of construction. Rework commonly happens due to insufficient supervision, poor workmanship, wrong or defective materials, etc. This research intends to determine the cost of waste and time delay due to reworks in the construction of reinforced concrete structure, to investigate the factors affecting the rework such as contractors, owners, and consultants. Also in this research the rework items, their frequencies, their correlation, and their impact on cost of waste and time delay were investigated. A case study project consisted of three 8-storeys buildings was observed and studied, and a questionnaire survey was undertaken among 22 construction projects to collect data. The case study and questionnaire survey findings revealed that, the reworks influenced the cost by 1.85% and 2.1% of construction cost respectively. Also the findings indicated that, the time delay of rework in case study and survey was 4.1% and 5.18% of construction duration respectively. It was obtained that, the major rework items affecting the cost were: 1- allocating inappropriate concrete materials, 2- changing the designed steel bar diameters due to unavailability, and 3- forming cold joint due to mismanagement of concrete delivering to the site. The major rework items that affecting the delay were: 1- collapsing excavation walls, 2- over excavation, and 3- falling formwork materials from top storeys that causes damage to them. Keywords: rework, cost, time, rework factors, reinforced concrete structure. ……………………………………………………………………………………………………………………………………………………………………………………………………………………