Concrete resists the effects of exposure, foreign agencies and other factors considerably better than many other building materials, and this is one of the reasons why it has established itself as a major construction material. However, because it is a composite material made up of several dissimilar materials and manufactured in the field, it is susceptible to a number of problems. When the surface of unhardened concrete develops a network of random cracks, the problem often is caused by plastic shrinkage. This shrinkage and the resulting cracks occur when the surface dries out and the concrete has not had time to develop sufficient tensile strength to resist cracking. The best way to prevent plastic cracking is to keep the concrete temperature between 60 and 75 degrees F. In general, crazing is applied to small, shallow, interconnected map cracks that occur over the surface of concrete. Crazing often occurs in concrete with a low strength surface containing an inordinate percentage of fines. To avoid crazing, trowel judiciously and at the right time. One of the most common complaints received from owners regarding concrete performance stems from concrete which is permeable. High strength, properly consolidated and properly cured concrete with low unit water content, optimum air entrainment and correctly positioned and constructed joints will be impermeable. Sand streaking occurs when there is insufficient cement paste of bind the sand particles together so pockets of sand result. Leaky formwork is the most common cause of sand streaking. Also discussed in this article were premature stiffening, honeycombing, slow strength gains, and uneven coloring.