Evaluasi Eksperimental Performa Beton Normal dengan Penambahan Retarder dan High-Range Water Reducer pada Kondisi Penundaan Pemadatan

Abstract

Delays in concrete compaction frequently occur in construction due to transportation, equipment, or site constraints, potentially reducing concrete performance. This study evaluates the effect of a retarder (Sika Plastocrete RT6 Plus) and a high-range water-reducing admixture (HRWR, Grolen HP-19R) on the workability, setting time, and compressive strength of normal concrete subjected to compaction delays of up to 120 min. Four concrete mixtures were investigated: control concrete, concrete with 0.3% retarder, concrete with 0.4% HRWR, and concrete containing a combination of both admixtures. The combined admixture significantly prolonged the initial and final setting times while maintaining workability during delayed compaction. The mixture containing 0.3% retarder and 0.4% HRWR retained a slump above 285 mm and achieved a compressive strength of approximately 32 MPa after 60 min of delay. Although slump remained relatively high after longer delays, compressive strength gradually decreased, indicating that prolonged delay adversely affected hydration efficiency. These findings demonstrate that the optimized combination of retarder and HRWR improves concrete performance under delayed compaction and provides practical guidance for concrete mix design in construction projects requiring extended workability.