基于环约束试验的混凝土早期开裂行为评价

Evaluation of Cracking Behavior of Concrete at Early-Age Based on Ring Test

采用2种外径相同、厚度不同的钢环,对C30,C50,C80这3个强度等级的混凝土进行了早期钢环约束试验,完整记录了从混凝土浇注开始直至贯穿性裂缝形成过程中钢环内侧不同位置处环向应变的发展,并对试验结果进行了详细分析.结果表明:钢环内表面环向应变的发展与混凝土收缩的发展趋势相同;对钢环内侧环向应变的实时跟踪,可检测混凝土收缩发展规律及可靠的开裂时刻;在所测试的2种厚度钢环中,厚度越小,测试灵敏度越高;相同厚度的钢环,在钢环中部测得的应变最大,底部次之,顶部最小;混凝土强度等级越高,钢环内表面环向压应变越大,混凝土开裂风险越大.

Two steel rings with the same external diameter, but the different thicknesses were used for the restrained ring tests on three kinds of concrete with different strength grade. The development of inner strain along the ring at three different height from top to bottom were recorded from concrete cast. The experimental results show that the development of inner surface strain of the steel ring coordinates well with the development of shrinkage stain of concrete. By tracking the inner surface strain of the steel ring the development of concrete shrinkage can be well found and the exact cracking time can be known. Re- garding sensitivity of measurement, the thicker the steel ring, the higher the measuring sensitivity. For the given ring thickness, the measured strain at the middle of the ring is the largest and at top is the smal- lest. The higher the strength of concrete, the larger the inner strain can be measured. Meanwhile, the cracking tendency is high also.