What are the causes of hollowing in waterproof mortar?
Release Time:
2015-08-21
Source:
What are the causes of hollowing in waterproof mortar?
Waterproofing of exterior walls is one of the critical issues that urgently need to be addressed in modern construction. With the widespread adoption of various new wall materials—such as concrete hollow blocks and aerated concrete blocks—the use of solid clay bricks, which were once extensively employed, has now been explicitly prohibited. However, these new wall materials generally exhibit high porosity and strong water absorption. Due to drawbacks such as poor strength and inadequate impermeability, it is essential to implement effective measures to prevent exterior wall leakage when using new types of wall materials. In the construction of exterior walls for high-rise buildings, quality problems such as cracking, crazing, hollowing, and spalling of the waterproof mortar layer—often caused by improper construction practices—can be broadly categorized as follows: The following are the reasons:
1. Layered scraping and coating were not performed as required.
Under normal circumstances, according to Waterproof mortar According to the construction requirements, scraping and coating are generally carried out in 2–3 coats. However, to accelerate progress, construction units often adopt a one-coat application method.
2. The grassroots level failed to handle the matter as required.
Holes and openings in the external scaffolding pipes were not sealed in multiple stages from the inside out; the wall surface was covered with dust and dirt; and the wall was excessively dry, with insufficient wetting. Under these conditions, applying the coating by troweling will inevitably compromise the strength of the waterproof mortar, as the moisture in the mortar is rapidly absorbed by the substrate.
3. The waterproof mortar mix ratio is inaccurate.
Failure to adhere to the specified mortar mix proportions as outlined in the design and relevant codes results in suboptimal performance of the waterproofing mortar, leading to issues such as inadequate waterproofing and poor crack resistance.
4. Add water for use after the adhesive slurry has hardened.
According to the waterproof mortar specifications, the prepared mortar slurry must be used up within 45 minutes, and no water may be added to the hardened slurry for reuse.
5. Inadequate curing after construction.
After hardening, waterproof mortar must be cured by sprinkling water. Following construction, the surface layer is exposed to the atmosphere for an extended period, where temperature fluctuations and drying winds cause shrinkage and cracking of the mortar finish.
