What can happen if subgrade is poorly prepared before concrete placement?

Poor preparation of the subgrade prior to concrete placement can have serious consequences for the overall integrity and performance of the concrete slab. If the subgrade is not properly compacted and stable, the weight of the concrete can cause it to settle unevenly, leading to a variety of structural issues.

When subgrade preparation is inadequate, the concrete can experience differential settlement. This means that some areas may sink more than others, creating stress concentrations that result in significant cracking. These cracks can affect not just the surface aesthetic, but they can also compromise the structural integrity of the concrete, leading to more extensive damage over time.

Additionally, a poorly prepared subgrade can cause inadequate support under the concrete, making it vulnerable to further settling after placement. This settling can create low spots that can hold water, leading to potential freeze-thaw issues in colder climates and further deterioration of the slab.

In summary, ensuring the subgrade is well-prepared is crucial to the longevity and performance of the concrete flatwork; inadequate preparation can ultimately lead to debilitating cracks and uneven settling that may require costly repairs or replacement of the concrete altogether.