ABSTRACT

The production process of 40.8-meter span Prestressed Concrete I-Girders (PCI Girder) at PT XYZ still encounters physical quality defects that contribute to rework and Cost of Poor Quality (COPQ). This study evaluates baseline process capability and formulates quality-control recommendations using the Six Sigma DMAIC framework. Observations covered 170 girder segments during peak production and 12 Critical to Quality (CTQ) parameters. The Measure phase using a U-Chart indicated a statistically controlled baseline process, with an 88.87% yield, 111,275 DPMO, and a 2.72 Sigma level. Pareto analysis showed that 99.56% of recorded defects consisted of Air Bubbles (73.57%) and Spalling (25.99%). Fishbone analysis identified contributing factors related to compaction practices, formwork/plinth conditions, mold oil application, demoulding before the required early strength was reached, and concrete temperatures above 35°C. Three cross-functional key informants representing Production Supervision, Laboratory, and Quality Control were involved in expert-judgment validation of the proposed improvements. The recommendations include 0.5-m vibrator insertion marking with 5–8-second intermittent vibration, concrete temperature control, a minimum early compressive strength of 50% before demoulding, Pre-Pouring Checklists, daily Toolbox Meetings, and periodic U-Chart/DPMO monitoring. Because post-implementation defect data were unavailable during the observation period, these actions are reported as expert-validated recommendations rather than quantitatively verified improvements. The study extends DMAIC application to segmental prestressed bridge girders by integrating statistical defect prioritization with cross-functional operational control recommendations.