As the construction industry continues to evolve, cast-in-place foamed concrete slabs have become increasingly popular, particularly in roof insulation projects. However, one persistent issue in their construction is the occurrence of cracks, which can significantly impact structural integrity. A variety of factors contribute to this problem. For instance, an improper mix ratio of foamed cement, excessive viscosity, and difficulty in expelling trapped air during vibration can lead to honeycombing on the surface of the hardened structure.
If the cement content is too high, the sand ratio too large, or the water-to-cement ratio too low, the fresh foamed cement mixture becomes excessively thick. This makes it challenging to discharge air bubbles, even within a viscous consistency. Poor workability of foamed cement necessitates addressing these issues from multiple angles—design, construction practices, transportation, and usage—all while ensuring rational application. Proper handling and optimization of materials are essential to minimize cracking risks.
Designers must account for various influencing factors and employ appropriate reinforcements and splits tailored to specific structural elements. Adhering strictly to established codes and mandatory regulations ensures compliance with structural requirements while minimizing the likelihood of cracks. Increasing the reinforcement ratio moderately can help mitigate shrinkage and crack propagation in foamed cement. Additionally, enhancing the effective slab thickness offers another means of improving structural performance.
The strength of cast-in-place foamed cement typically ranges from C15 to C30, requiring steel reinforcement that meets crack-resistance criteria. Technical solutions should address overlapping and reserved openings for pre-installed conduits to preserve slab thickness and effective crack-resistant depth. It’s equally critical to manage raw material quality rigorously, ensuring all components align with design specifications and national standards.
Optimizing the mix design of foamed cement involves adding high-efficiency water reducers and reducing the water-cement ratio. During construction, steel reinforcement must be securely tied, conduits pre-installed, and openings reserved accordingly. Effective measures should guarantee accurate slab thickness and precise steel placement. Template supports must be robust, offering adequate strength and rigidity, with mold removal timed appropriately. Templates should also be treated with a release agent, and stacking heavy loads on the roof during construction is strictly prohibited.
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