【Haichuan Construction Technology】Advantages and Disadvantages of Post-cast Joints

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Advantages and disadvantages of post-cast strips: Post-cast strips are primarily used to address concrete shrinkage stresses during construction and to eliminate differences in settlement. However, their use also has certain disadvantages, which are particularly evident in the case of waterproof concrete. 1⃣️ Advantage: Reduces concrete shrinkage stress: By pouring concrete in temporary sections and in stages, cracks caused by early-stage shrinkage deformation are minimized. Adjusting settlement differences: Through phased construction, the settlement of buildings of different heights, such as the main building and the podium, is brought to be consistent. Construction convenience: As a temporary structural joint, it reduces construction difficulty and costs. 2⃣️ Disadvantages: Leakage risk: If construction is not done properly (such as inadequate fixing of formwork or an unstable support system), it can lead to leakage of concrete or to concrete flowing into the post-construction joints, thereby compromising the structural safety. Extended construction period: It is necessary to wait until the settlement of the main structure stabilizes before sealing it (usually 1-2 months), which results in an extended construction timeline. Maintenance is complex: the post-cast strip must be poured at a specific time, using high-strength concrete, and requires strict control during construction. 3⃣️ Response: In underground foundations where the slip-form construction method is available, this method should be used as much as possible to create \"seamless\" concrete. The location of the post-cast strips should be chosen carefully, avoiding structural load points and waterproofing areas. It is advisable to integrate them with settlement joints and expansion joints in the design, in order to minimize the use of such post-cast strips. When installing post-cast strips on concrete with waterproof properties, it is necessary to combine them with water-stop sheets, as well as adopt specialized construction techniques for prefabrication and subsequent pouring, in order to focus attention on these areas where the quality might be compromised during construction.