EXPERIMENTAL EVALUATION OF DUCTILITY AND STIFFNESS OF FLEXIBLE BEAM WITH INSTANT CONCRETE MATERIAL AT 7 AND 28 DAYS

Abstract

This study aims to evaluate the collapse behavior, ductility, and stiffness of reinforced concrete beams based on instant concrete at 7 and 28 days of age, which are still relatively rarely studied. Instant concrete is a ready-to-use material with a controlled mixture composition that produces consistent concrete quality without the need for mixture redesign. The research was conducted experimentally on flexural beams with a 2D10 main reinforcement configuration and D8-50 mm stirrups with a target concrete compressive strength of 25 MPa. The tests included reinforcement tensile strength tests, cylinder compressive strength tests, and beam flexural strength tests using two-point loading with the displacement-controlled method at a ratio of a/d = 3.259 until failure. The results showed that all concrete compressive strength values met the quality acceptance limits, with no results below 3.5 MPa from the target value. The results also showed that the beams had high ductility > 4 based on FEMA, indicating a significant deformation capacity before failure. The stiffness of the beams at both ages was also in the good category. The crack pattern was dominated by vertical flexural cracks with a gradual collapse mechanism, reflecting the ductile and safe behavior of the beams. Overall, instant concrete proved to be effective in accelerating construction and providing good structural performance.