The demand for infrastructure continues to grow, including diaphragm walls, which are used in many projects. However, large-scale constructions often rely on conventional lap splicing composed of market-length rebar for rebar connections, leading to significant waste due to the required long overlapping lengths. This reliance stems from a limited understanding of special-length rebar and mechanical couplers, which have been shown to reduce rebar waste and consumption effectively. Furthermore, the broader advantages of couplers, particularly in terms of cost savings and improved productivity, remain largely unrealized, as engineers may delay implementing them due to perceived planning complexities. This study aims to quantify the impact of minimizing rebar waste through the integration of special-length rebar and couplers, focusing on their impact on cost reduction and productivity improvements in large-scale diaphragm wall projects. The findings indicate reductions in waste by 95.41%, rebar usage by 17.95%, and total costs by 8.17%, along with improved rebar productivity by 84.4%. These results highlight the significant benefits of employing couplers and a special-length-priority optimization approach, extending their advantages beyond waste reduction. These findings contribute to a deeper understanding of how innovative rebar solutions can enhance efficiency and improve overall project outcomes in construction. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.