How To Avoid Concrete Cracks During Construction?
During the construction process, avoiding concrete cracks is a crucial link, which is related to the overall quality and safety of the building. Here are some effective preventive measures:
1. Material selection and proportion
Strictly control the water-cement ratio: When preparing concrete, strictly control the water-cement ratio to avoid high water consumption per unit volume or excessive cement addition, which helps to reduce the shrinkage of concrete and improve crack resistance.
Choose high-quality raw materials: Select qualified raw materials such as cement, sand and gravel, and test the stability of cement, free calcium oxide content, etc. to ensure that they are qualified.
Reasonably add admixtures: In the preparation of large-volume concrete, retarding, water-reducing, and micro-expansion admixtures can be added to improve the performance of concrete and reduce the occurrence of cracks.
2. Construction process control
Vibration compaction: Concrete should be vibrated and compacted to eliminate bubbles in it, so that the concrete is densely combined and the early crack resistance is improved.
Secondary vibration: Secondary vibration within 1 to 4 hours before the initial setting of concrete usually achieves better results, which can effectively improve the density of concrete and reduce settlement cracks.
easonable pouring sequence: By optimizing the pouring sequence, the internal and external temperature difference of concrete can be better controlled to prevent temperature stress caused by excessive hydration heat. At the same time, the construction method of split-slot and segmented pouring is adopted to decompose large blocks of concrete into small blocks, effectively reducing temperature stress.
Surface treatment: The surface treatment of concrete should be carried out separately before initial setting and final setting, and it should be smoothed with iron plate or smoothed with wooden trowel to reduce surface shrinkage cracks.
3. Maintenance and protection
Timely maintenance: After concrete pouring, it should be covered with moist materials in time to keep the concrete surface moist to prevent cracks caused by too fast evaporation of water. In winter, insulation maintenance measures should be taken.
Strengthen temperature measurement management: For large-volume concrete, temperature measurement management should be strengthened to ensure uniform temperature inside the concrete and avoid cracks caused by excessive temperature difference.
Appropriately extend the insulation and demoulding time: When constructing at low temperature in winter, the insulation and demoulding time should be appropriately extended to make it cool down slowly to prevent cracks caused by sudden temperature changes.
4. Construction management
Strengthen construction management: Ensure that the construction process is reasonable and the operation is standardized. Train construction personnel to improve their skills and quality awareness.
Strictly abide by the time and order of formwork removal: When removing the formwork, follow the principle of "support first, then remove, and then remove", and pay attention to gently remove and place to avoid damage to the concrete structure. Maintenance work should be carried out immediately after the formwork is removed.
5. Other precautions
Avoid premature transportation and stacking of heavy objects: Before the concrete of beams and slabs reaches the design strength, avoid transporting and stacking a large amount of engineering and construction materials on them to prevent the beams and slabs from vibrating or fracturing them.
Dealing with hollowing of the base layer: For cracking problems caused by hollowing of the wall base layer, plain cement slurry or polymer cement slurry should be used for brushing and wet maintenance, or layered plastering and other methods should be used for treatment.
Avoiding concrete cracks requires starting from multiple aspects, including optimizing concrete mix ratio, strengthening concrete mixing and transportation management, standardizing formwork operations, reasonable construction technology, strengthening construction maintenance, reasonably designing expansion joints, and paying attention to construction details. The implementation of these measures will help improve the overall quality and durability of concrete projects.
