Predicting the Compressive Strength of Concrete Containing Recycled Fine Aggregate Using Early Age Test

The present research aims to make an attempt to predict the compressive strength for 28 and 56 days of concrete containing recycled fine aggregate by taking advantage of the compressive strength for early ages for the same mixture. Four groups of concrete mixtures were prepared, the variable in the groups is the compressive strength (25, 30, 35, and 40MPa), and for each strength, the natural fine aggregate was replaced with four different percentages of recycled fine aggregate (RFA) (0, 10, 20, and 30%) as volume ratios. After standard curing (water immersion) of the concrete samples, they were tested to obtain the compressive strength at different ages (3, 7, 28, 56 days), and based on experimental results, mathematical models were made through which the compressive strength for 28 and 56 days can be predicted based on the results of the compressive strength for 3 and 7 days. According to the proposed mathematical models, early age tests may be utilized to predict the compressive strength of concrete at 28 and 56 days, where the values of the determination coefficient for 28 and 56 days of compressive strength based on (3 and 7) days compressive strength were (84.8%), (86%), (79.2%). and (79.2%), respectively.