Pengaruh Variasi Superplasticizer dan Accelerator terhadap Workability dan Kuat Tekan Beton High Early Strength Berbasis Silica Fume dan Serat Polypropylene

Abstract

The excessive use of admixtures in High Early Strength (HES) concrete often triggers an imbalance between early strength development and workability. This study aims to analyze the simultaneous effects of four types of admixtures on workability and compressive strength characteristics, as well as to identify the optimal mix composition for HES concrete with a target strength of f'c 40 MPa. The research method employed a quantitative laboratory experimental approach by varying the concentrations of accelerator 1,5%, 2,5%, dan 3,5% and superplasticizer 1,7%, 2,3%, dan 2,6%, while keeping the contents of silica fume 5% and polypropylene fiber 0.025% constant. Testing included the slump flow of fresh concrete and the cylinder compressive strength at ages of 4, 6, 8 hours, and 28 days. The results showed that the highest slump flow value was achieved by the 1.5% accelerator + 2.6% superplasticizer variation at 610 mm, whereas the highest 28-day compressive strength was obtained by the 3.5% accelerator + 1.7% superplasticizer variation at 69.14 MPa. The superplasticizer was proven to enhance workability, while the addition of accelerator reduced slump flow but significantly accelerated hydration and early strength development. Regression analysis indicated a negative correlation y = -0.076x + 108.45, where excessive fresh concrete workability tended to decrease compressive strength. It is concluded that the 3.5% accelerator variation is the most optimal composition to produce massive early compressive strength development without compromising the final concrete quality, making it highly recommended for rapid construction applications and the precast industry.