Concrete, known for its strength and durability, is a common building material used in various construction projects around the world. However, despite its robust nature, concrete is susceptible to cracking, which can compromise its integrity and visual appeal.

Understanding the causes behind these cracks and implementing appropriate solutions is crucial for ensuring the longevity and safety of any concrete structures.

Non-Structural Cracks

1. Crazing

Crazing appears as a network of fine cracks on the concrete surface, resembling a spider web. It typically occurs due to rapid drying of the concrete surface before it has fully cured. This rapid drying causes shrinkage stresses, leading to the formation of these surface cracks.

Causes:

• Rapid evaporation of water from the concrete surface in hot or windy conditions.
• Insufficient curing methods, such as inadequate moisture retention

Solutions and repair:

• Craze cracks don’t open and close with time and can be covered using a quality paint and can be aided through the application of a glass fibre tissue during the painting operation, if necessary.
• Use curing compounds or membrane-forming curing agents to slow down the evaporation rate.
• Apply wet burlap or plastic sheets to the surface to retain moisture during the initial curing period.
• Avoid plastering in extreme weather conditions or employ shading and windbreaks to mitigate rapid drying.

2. Plastic Shrinkage Cracking

Plastic shrinkage cracking occurs during the early stages of concrete curing when the concrete is still in a plastic or fluid state. Like crazing, it results from rapid moisture loss and subsequent shrinkage of the concrete surface.

Causes:

• Evaporation due to high ambient temperatures and low humidity levels.
• Use of high water-to-cement ratio in the concrete mix.
• Application of plaster to substrates that have not been pre-wetted to prevent loss of moisture.

Solutions and repair:

• Ensure that the optimum water content is used by measuring off water when mixing plaster. The use of a hosepipe without measuring water is not advised.
• Employ shading, fogging, or windbreaks to reduce evaporation rates.

For expert advice on the correct cement products to use to achieve the best possible results contact the Sephaku call centre on 0861 32 42 52 or speak to your technical representative.