What is a common cause for cracking in concrete?

Poor mixing is a common cause for cracking in concrete due to its impact on the uniformity and consistency of the material. When concrete is not mixed properly, it can lead to an uneven distribution of components such as cement, water, and aggregates. This inconsistency can create weak spots in the concrete, resulting in increased susceptibility to cracking as the material cures and hardens. Additionally, inadequate mixing may lead to a problem known as segregation, where heavier aggregates settle at the bottom, causing a lack of cohesion in the final product, further increasing the chances of cracking.

In contrast, while rapid curing and low water-to-cement ratios can also contribute to cracking, they do so in different ways. Rapid curing may cause the surface to dry too quickly, leading to surface cracks rather than structural issues. A low water-to-cement ratio can enhance the strength of concrete, but if it is too low, it can lead to difficulties in mixing and placing the concrete, potentially causing cracking during or after the curing process. Excess elongation, which typically concerns materials like bricks or metals under tension, is less relevant as a primary cause of cracking in concrete. Thus, poor mixing stands out as a direct and consistent factor contributing to this issue.