8 common concrete problems and how to solve them

Cement and concrete are vital for modern construction. Cement acts as a binding agent, and concrete offers versatility, durability, and strength. They contribute to sustainable development, are recyclable, energy-efficient, and help reduce carbon emissions. To maintain the construction project's structural integrity and aesthetics, we have prepared a guide to some typical concrete issues, along with their solutions and prevention measures.

1. Cracks:
Identify the type of crack (like shrinkage, settlement, structural) to determine the underlying cause.

• Shrinkage cracks: Thin, straight, caused by concrete drying and shrinking.
• Settlement cracks: Reflect uneven support beneath concrete, often wider at one end.
• Structural cracks: Wider, deeper, caused by excessive loads or foundation movement.
   

Prevention:

• Proper mix design and adequate curing to minimise shrinkage.
• Use of control joints to manage crack locations.
• Ensure proper subgrade preparation to prevent settlement.

2. Scaling:
Scaling occurs when the concrete surface flakes off due to freeze-thaw cycles or poor finishing practices. For instance, overworking the surface during finishing can weaken surface integrity and failure to adequately seal the surface.

Prevention:

• Use air-entrained concrete in regions prone to freezing temperatures.
• Proper curing methods include covering the concrete with plastic sheeting or curing compounds.
• Please don't finish concrete prematurely when bleed water is still present.

3. Spalling:
Spalling is the chipping or breaking off of concrete surfaces, often due to corrosion of reinforcement or freeze-thaw cycles.

Prevention:

• Adequate concrete cover over reinforcement to protect against corrosion.
• Use of corrosion inhibitors or stainless steel reinforcement.
• Proper drainage and waterproofing to prevent water penetration.
   

4. Surface Crusting:
Surface crusting appears as a thin layer of weak concrete on the surface, often caused by improper finishing techniques or rapid evaporation of surface water.

Prevention:

• Use fog sprayers, evaporation retardants, or windbreaks to slow down surface water evaporation.
• Proper timing of finishing operations to avoid premature drying.
• Adequate curing measures to maintain moisture levels in the concrete.

5. Dusting:
Dusting occurs when the surface of concrete becomes powdery due to poor mix design, over-troweling, or improper curing.
 

Prevention:

• Use of proper mix proportions with adequate cement content.
• Avoid over-troweling during finishing to prevent weakening of the surface.
• Ensure adequate curing to promote strength development and reduce surface dusting.

6. Discoloration:
Discolouration can result from various factors, including improper curing, inconsistent mixing, or contamination during placement.

Prevention:

• Consistent mixing and batching practices.
• Proper curing methods, such as moist or curing compounds, prevent uneven hydration and discolouration.
• Prevent contamination during placement by maintaining clean equipment and formwork.
   

7. Honeycombing:
Honeycombing appears as voids or gaps in the concrete surface, often due to inadequate compaction or poor formwork.

Prevention:

• Proper vibration and compaction during concrete placement.
• Ensure proper formwork design and construction to prevent leakage and complete mould filling.
• Proper consolidation techniques to eliminate air voids and ensure proper concrete compaction.
   

8. Alkali-Silica Reaction (ASR):
ASR occurs when alkalis in the cement react with certain types of aggregate (like gravel, crushed stone, sand, Recycled concrete aggregate (RCA) or crushed slag), leading to expansion and cracking over time.

Prevention:

• Use of low-alkali cement or supplementary cementitious materials.
• Selection of non-reactive aggregates.
• Proper mix design and testing to identify potential reactive aggregates.
   

Construction professionals can ensure durable and aesthetically pleasing concrete structures by understanding these common problems, implementing effective troubleshooting techniques, and employing preventive measures. Regular inspection and maintenance are essential for identifying and addressing issues before escalating.