Are hairline cracks in fresh concrete normal?

Yes, in about a month, fine cracks should disappear. While shrinkage cracks can appear on the surface within hours of pouring concrete, it takes a full month for new concrete to fully settle. Don't be surprised if the cracks that seemed visible at first are almost impossible to see after a month of settlement. Fine cracks are commonly observed in freshly laid concrete and their appearance is due to the phenomenon of plastic shrinkage.

As the name implies, these cracks are very small, about 0.003 inches (0.08 mm) wide and can be very shallow. A well-made concrete structure should not develop structural cracks quickly. However, fine cracks can be expected. Don't stress; these cracks are not a sign of poor quality and can be fixed without much effort.

Yes, in about a month, fine cracks will disappear. Concrete naturally cracks on its own, unless it is given a place to crack, such as a control joint or expansion joint. As concrete cures, heats up and expands. In summer, I saw the slab crack before I could walk on it.

The main cause of fine cracks in concrete is shrinkage. Concrete is poured wet and then dried. As concrete dries, it becomes hard and strong. This process is called healing and can take a total of 28 days to complete.

But it's the first day that's most important to prevent fine cracks. If concrete loses moisture too quickly, small cracks can form. To avoid this, reduce the speed of the drying process by keeping the concrete surface moist. There are two main ways to do this.

As the concrete cures, excess water evaporates and the volume of the concrete at the inlet is reduced. The main cause behind the generation of fine cracks in concrete is plastic shrinkage, which is the rapid depletion of moisture from fresh concrete into its plastic state. For a narrow crack like this, you can use a self-leveling concrete crack filler to seal the crack before painting or finishing the surface. Big D Ready Mix Concrete has been serving customers in the Dallas, TX area since 2002, with more than 400 utility mixes, heavy-duty wall mixes, exposed aggregate mixes, flexural strength mixes, stamped concrete mixes, fluid fill mixes, grout mixes and mixes for trailer pumps.

If cracks appear right after pouring a concrete base, the concrete may have dried too quickly, mixed poorly, or overworked. ACI 116R-90, Cement and Concrete Terminology, defines fine cracks as cracks in an exposed concrete surface that has widths so small that they can barely be perceived. The causes of these cracks can be due to variations in air temperature, concrete temperature, relative humidity and wind speed on the concrete surface. Repairing a fine crack in a concrete structure involves filling the space with a material that adheres well to the concrete, restores its original appearance, and prevents liquids from penetrating inside the structure and staining the concrete.