Comparative Analysis of Cost and Time of Implementation of Precast and Cast in Situ Work Using the CPM (Critical Path Method) in the Purwosari – Malingmati Road Reconstruction Project in Bojonegoro Regency

Abstract

Road infrastructure is a crucial element in supporting the mobility of goods and people, while also contributing to economic growth and community welfare. The Purwosari–Malingmati road reconstruction project in Bojonegoro Regency faces challenges related to limited time and budget, making the selection of an efficient construction method essential. This study aims to analyze the comparison of time and cost between precast and cast in situ methods using the Critical Path Method (CPM). The research method employed is quantitative, descriptive, and comparative. Data were obtained from project documents and field observations, then analyzed to calculate the realization duration and total cost of each method. Time analysis compared planned and actual durations, while cost analysis covered all direct and indirect components, including materials, labor, equipment, and supporting expenses. Comparisons were conducted on similar work units to ensure objectivity. The results show that the precast method completed the work in 17 days—faster than the cast in situ method, which required 18 days—with a critical path of 12 days. In terms of cost, precast amounted to Rp 4.87 billion, while cast in situ reached Rp 18.20 billion (273% more expensive). Non-critical activities in the precast method could be carried out in parallel, thereby increasing efficiency. The time acceleration of the precast method was recorded at 19%, while cost savings were significant compared to cast in situ. In conclusion, the precast method is more effective and efficient in the context of this project—both in terms of time and cost.