Concrete is one of the materials that are often used in construction works, however work that uses concrete material is almost impossible to do at one time. Damage of the mixer lane, the volume of concrete, and the capacity of the batching plan cannot meet the demand causes delays in the casting process that causes cold joints. This study aims to analyze the effect of the addition of polypropylene fibers on the value of beam flexural strength and compare with concrete beams without additional polypropylene fibers due to the presence of cold joints using the experimental method. The specimens used were normal reinforced concrete blocks with 12 polypropylene fibers added to each specimen, the samples were 2 beams without additional polypropylene fibers and 2 beams without additional polypropylene fibers to be tested in a vertical and horizontal direction. The method of making mixtures refers to the mix design ACI 211.1-19 with a concrete pouring time interval used in the process of making specimens namely 120 minutes and 240 minutes by testing the flexural strength of the test object at the age of concrete 7, 14,and 28 days. From the testing of the four beams, it was found that cold joint concrete beams without additional polypropylene fibers at 28 days of concrete had greater flexural strength than cold joint concrete with additional polypropylene fibers in both vertical and horizontal directions, and the horizontal direction is greater flexural strenght than the vertical direction.