后张预应力混凝土结构灌浆空洞X射线无损检测的试验研究

利用国内现有的钢结构X射线探伤设备，对后张预应力混凝土结构中灌浆空洞和预应力筋束的断丝进行无损检测的试验研究。基于混凝土内空洞的X射线透照原理，提出了波纹管内灌浆空洞的透照方法及技术指标，包括管电压、曝光时间、焦距和灵敏度等。不同强度和不同厚度混凝土试块的透照试验表明：在相同的照片黑度范围内，透照同标号混凝土的管电压和曝光时间随着混凝土厚度的增加而明显增加；在相同的透照参数下，同厚度不同标号混凝土的照片黑度差异较小；混凝土一钢材的厚度等效系数可近似取为0．2。最后，在对大量底片分析研究的基础上，给出了判别金属波纹管和PVC波纹管（包括圆形和扁形两种形式）内灌浆空洞及预应力筋束断丝的方法和步骤。

Experimental Study of Grouting Voids of Post-tensioned Prestressing Concrete Structure by X-ray Penetration Method

Utilizing the current X-ray facilities dedicated for nondestructive testing of steel structures,nondestructive tests were carried out to investigate the grouting voids and tendon rupture in post-tensioned prestressing concrete structures.The testing procedure and technical parameters,namely tube voltage,exposure time,focal distance and sensitivity,for detecting grouting voids in sheath were proposed based on the principle of X-ray penetration.The experiments on concrete specimen with different strength and thickness reveal that a rapid increase in the tube voltage and exposure time with the increase of concrete thickness for the same density range of radiograph;however,for same penetration factors,the density of radiograph is almost independent of the concrete strengths.The concrete-steel thickness equivalent factor can be about 0.2.Finally,from a systematical study on a large quantity of radiographs,the approach and procedure to detect the grouting voids within metal or PVC sheath(including both round and elliptic shaped ones)and rupture of tendons were presented.