Effect of Retarder Usage on Concrete Characteristic

This research is experimental research aimed at to investigate the effect in using retarder onto concrete workability and compressive strength. The sample will be made of concrete cube with uniform size is 15 cm x 15 cm x 15 cm. the total amounts of cube are 96 pieces, each 32 samples for each data groups into 0%, 1%, 2% and 4%, the sample are then kept fresh with various time, 0 minute, 10 minutes, 15 minutes and 20 minutes. The fresh sample’s feasibility and compressive strength will be examined at 7, 14, and 28 days concrete. The result shows workability concrete changing in case retarder addition. The higher retarder concentrations cause either increased slump value or easy-made concrete. The longer fresh concrete are storage will result in decreased in slump value or the concrete is viscous. In concrete with age 7, 14, 28 days, the highest pressure strength is 2%. Additions in 4% retarders are significantly degraded pressure strength. Concrete storage up to 20 minutes does not give significant concrete pressure strength.