Derivation of Bulk-Volume Aggregate Conversion Factor Through Analysis of Ready-Mixed Concrete Shipment Data in Korea

In South Korea's national aggregate supply-demand planning, ready-mixed concrete (RMC) shipment has served as the key indicator for estimating aggregate demand; however, the conversion factor = 1.25 (Lee and Hong, 2021;Lee et al., 2024) used to translate RMC shipment volume into aggregate volume was a conventional volume coefficient, overestimating aggregate demand by approximately 11%.Furthermore, because the accuracy of this conversion factor () had not been verified, assessments of aggregate supply-demand balance lacked sufficient reliability.This study therefore re-derives the aggregate bulk-volume conversion factor per 1 m of RMC for supply-demand balance assessment, using standardized RMC shipment data.Strength-class distributions of government-procured RMC (2018-2024) were calculated from transaction records of the Korea ON-line E-Procurement System (KONEPS), yielding = 1.13 (CV = 0.53%) based on the KS F 4009 strength classification combined with KONEPS mix-design data.This value matches the lower bound of the American Concrete Institute (ACI) 211.1 theoretical range (1.13-1.30),confirming consistency with internationally accepted figures.Independent cross-validation using domestic cement shipment data also confirmed the consistency between the two datasets, with a discrepancy of only -5.8% between cement-derived RMC volume and association-reported shipment.Consequently, revising from 1.25 to 1.13 raises the national aggregate sufficiency rate from 73.5% to 81.3%; yet the rate remains below 100%, confirming that the previously reported "supply surplus" assessment should in fact be characterized as "actual deficit in the market places."These findings provide a basis for reestablishing the demand estimation framework underlying national aggregate supplydemand planning, although further investigation is needed to identify the specific causes of this supply-demand gap.