In a city where prefabricated construction is rapidly expanding, some prefabricated concrete shear wall residences have experienced water leakage through the horizontal joints of the exterior shear wall panels after being put into use. To address this issue, developers and design institutes have implemented structural measures such as raising the connection between the wall panel and the cast-in-place concrete strip above ground level to facilitate repairs, and installing tongue-and-groove waterproof structures at the panel joints.
However, Mr. Guo Xueming, an expert in prefabricated construction, emphasized that while enhancing waterproofing at the exterior wall panel joints is important, leakage at the horizontal joints indicates a serious structural risk.
1) Leakage at the horizontal wall panel joint indicates incomplete grouting at the joint.
2) If the horizontal joints are not fully grouted during construction, it becomes difficult to ensure full grouting in the sleeves or anchor holes above the joints. This compromises the reliability of the longitudinal steel bar connections within the structure, posing a significant safety hazard with potentially severe consequences.
3) Furthermore, leakage at these horizontal joints exposes the longitudinal steel bars to corrosion, greatly reducing the structure’s durability.
Mr. Du Changling, a specialist in prefabricated concrete construction, highlights that the most critical aspect of prefabricated concrete work is the connection of longitudinal steel bars, with grouting being the key operation. It must be complete and thorough.
Mr. Wu Hongbing, an expert with extensive experience in prefabricated concrete construction management in Japan, led the installation of a 100,000 square meter prefabricated concrete factory building in Dalian in 2017. He stresses that the sealing of the grouting area must be airtight. If leakage occurs, the grout already injected must be thoroughly washed out with high-pressure water, resealed tightly, and then re-grouted. Cutting corners in this process can lead to major structural safety issues.
Mr. Li Ying, another expert trained in Japan, explained that to develop an effective grouting process, Japanese engineers create a 1:1 scale transparent acrylic model of component joints. This allows them to observe grout flow, air exhaust, and completeness of filling, enabling them to establish proper grouting procedures to prevent insufficient grouting.
Among more than ten common quality issues in prefabricated concrete construction, the experts unanimously agree that incomplete or inadequate grouting is the most critical and unacceptable problem. Grouting must be executed flawlessly without any compromise.
Experts agree that while grouting is not inherently difficult, ensuring its quality depends on several key factors:
1) Project managers must have a thorough understanding of the principles, technical requirements, and procedures involved in grouting.
2) Grouting workers should receive rigorous, comprehensive training and be certified to perform the work.
3) Strict adherence to operating procedures during grouting is essential.
4) Technical quality control and supervisory staff must conduct on-site monitoring and inspections.
5) Mobile monitoring equipment should be employed to track and document the entire grouting process for quality assurance.
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