Abstract: Based on long-term crack width experiments on recycled aggregate concrete(RAC) beams with different recycled material replacement rates, the development of crack widths over time between the different beams was compared. The results show that the period of rapid cracking growth is postponed in recycled aggregate concrete beams, and also of longer duration than in normal concrete beams. The internal lever arm coefficient, average crack spacing, and steel strain non-uniformity coefficient were fitted, and a formula for calculating maximum short-term crack width is established. Its calculation results have satisfactory precision. After analyzing additional crack width time-varying coefficients, formula for maximum crack width an RAC beam with varying replacement rates is established.