Has your concrete cracked?

The initial response to cracking is that there must have been something wrong with the concrete when it was delivered. Not so, most surface cracks in concrete slabs are usually as a result of aftercare.

The main culprits behind concrete cracking are typically

1. Lack of or ineffective curing after finishing.
2. Premature or rapid drying leading to surface tension build-up, culminating in cracks. The occurrence, direction, and size of these cracks can vary significantly depending on weather conditions during placement, including temperature, humidity, and wind speed. This is when the rate of evaporation exceeds the rate of bleed and results in plastic shrinkage cracking.

Interestingly, some customers who have never applied curing to concrete might claim to have never incountered cracks. However, micro cracks could have formed, invisible to the naked eye. Improper curing can render concrete surfaces up to 50% less durable, susceptible to dusting, and delamination.

Characteristics of Plastic Shrinkage Cracks

Cracks may manifest within hours of concrete finishing, though they often become visible only the next day. Despite appearing solely at the surface, they can extend throughout the slab’s thickness. It’s crucial to understand that these cracks, aren’t considered structural and don’t compromise the overall integrity of the slab.

For slabs serving as direct wearing courses (like driveways or warehouse floors), surface durability might become a concern. These cracks can vary in width from hairline to a few millimetres and may appear randomly or in a discernible pattern.

Repair

The most efficient method to address cracks is by brushing dry cement powder over them. The cement fills the crack, and residual water within the concrete activates it, creating a seal. If left untreated, water infiltration could exacerbate edge and internal damage through freeze-thaw cycles.