【Haichuan Chemical Construction Technology】Why have water-stop steel plates for post-cast strips been explicitly banned in many areas across the country? ?

Thread Content

Why have many areas across the country explicitly abolished the water-stop steel plates used in post-cast strips! ? The problem lies in the transition from theory to actual construction. The water-stop steel plates that are perfect in the laboratory and on blueprints turn out to be full of problems once they arrive at the construction site. The current design of these water-stop steel plates presents two insurmountable issues. The first problem is that the water-stop steel plate acts like a sieve; the debris generated during concrete pouring, the dust that falls to the ground, and the binding wires all accumulate beneath the steel plate. With those narrow gaps of just a few centimeters, tools cannot get in, and water guns cannot reach the appropriate locations, so it’s common for the area to not be cleaned properly. The second problem is even more serious: after concrete is poured, the area right below the steel plate gets blocked by the concrete itself. This prevents the vibrator from reaching deep enough and ensures uneven vibration; as a result, bubbles cannot be removed and voids cannot be filled. The area beneath the steel plate ends up full of holes similar to those in a honeycomb. What was supposed to act as a barrier against water leakage actually becomes a factor that contributes to leakage. Water no longer flows around the steel plate but passes directly through the unfilled voids beneath it. This is why, in many projects, even though waterproof steel plates are used in accordance with specifications, leaks still occur in the post-cast joints. Thus, the direction of the new regulations is clear: the physical water-blocking structure, which is difficult to implement perfectly on construction sites, is removed and replaced with high-performance concrete containing admixtures that provide resistance to seepage, crack formation, and self-repair capabilities. It’s not that waterproofing is no longer needed; rather, a different method of waterproofing is adopted one that better suits the actual conditions of on-site construction. The admixtures prevent water from seeping through capillary pores within the concrete, and the concrete can repair itself once cracks appear, unaffected by rebar, steel plates, or confined spaces. Even areas that were not properly compacted during pouring become dense as well. The difference between old and new methods lies in this very aspect: waterproof steel plates require manual installation, welding, cleaning, and vibration by workers to ensure quality; if anything goes wrong at any of these stages, all the effort is in vain. On the other hand, water-resistant and crack-preventing admixtures utilize the inherent properties of the materials to provide waterproofing, shifting the focus of waterproofing from reliance on construction precision to the materials themselves. Currently, some projects are using high-water-resistant concrete with self-healing properties at the post-cast joints, in combination with full-section waterproofing systems, to replace water-stop steel plates. It’s not that waterproofing is unnecessary; rather, a material solution that better suits the actual conditions on site is employed to address the problem of leakage in these key areas effectively. Waterstop sheets are not useless; their merits are recorded on the blueprints, while their shortcomings lie hidden beneath the poorly compacted sheets. The new regulations that eliminate them are the result of practical engineering experiences driving the evolution of standards – by relying on more controllable materials for waterproofing the post-cast strips rather than on human skill. Only by following this approach can the long-standing problem of basement leaks be truly solved.