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预应力电杆蒸养脱模后,常因预应力筋回缩而成为废次品。经过对我厂电杆的分析,钢筋回缩的主要原因有以下四个方面。一、蒸养不足由于蒸养时间或温度、汽压不足,电杆脱模时,砼强度低于设计强度的70％,抵抗不住预应力钢筋压力而造成钢筋回缩。二、下料长度误差凡出现同根电杆个别钢筋回缩,其下料长度相对误差均较大,最大可达5mm左右。下料长度相对误差越大,应力相差也越大,因此造成较短的钢筋对砼的预压力增大而产生回缩。若短筋随机分布到一边,还会造成杆身严重弯曲。三、原材料选用或处理不当 1.水泥比重过小由于水泥比重过小,离心浮浆严重,集料处少浆,
After the prestressed poles are steamed and demoulded, they often become defective due to shrinkage of prestressed tendons. After analysis of the poles in our factory, the main reasons for rebar retraction are as follows: First, lack of steaming due to steaming time or temperature, steam pressure is insufficient, when the pole is demoulding, the strength of the concrete is lower than 70% of the design strength, and it cannot resist the prestressed steel bar pressure and cause the steel retract. Second, the length of the length of the error where the same root pole individual rebar retraction, the relative error of the length of the blanking are relatively large, up to about 5mm. The larger the relative error of the blanking length, the greater the difference in stress, resulting in shorter rebar preload on the jaw and increased retraction. If the short ribs are randomly distributed to one side, it will cause serious bending of the shaft. Third, the selection of raw materials or improper handling 1. The proportion of cement is too small due to the proportion of cement is too small, centrifugal levitation serious, less aggregate at the aggregate,