外加剂及聚丙烯纤维对混凝土早期裂缝影响的实验研究

Experimental study of the influence of intrusion aid and polypropylene fiber on early drying shrinkage cracks of concrete

采用平板法测试混凝土在干燥条件下的早期开裂情况.研究外加剂(减缩剂、膨胀剂)和聚丙烯纤维等材料的单掺或复掺对混凝土早期干燥收缩裂缝的影响规律.实验结果表明:膨胀剂使混凝土裂缝数量明显减少,对最大裂缝宽度影响不明显;纤维能阻止裂缝的扩展和延伸,使大裂缝细化、分散,而不能从根本上消除裂缝;减缩剂显著提高混凝土的抗裂性能,抗裂效果最好;膨胀剂、聚丙烯纤维以及减缩剂的双掺或三掺对混凝土抗裂性能的影响与单掺相比较区别不大.

Early drying shrinkage cracks of concrete were tested by slab drying experiment. The influence law of intrusion aid（ shrinkage reducing agent, expansive agent）and polypropylene fiber on early drying shrinkage cracks of concrete was studied. Experimental results show that the expansion agent can significantly reduce the number of concrete cracks and can＇t significantly reduce the largest crack width. Polypropylene fiber can inhibit the expansion and extension of cracks, and decentralize the big cracks, but it is impossible to fundamentally eliminate cracks. Shrinkage reducing agent can significantly improve crack-resistance capability of concrete, and have best effects. The double-doped and multi-doped shrinkage-reducing agent, expansive agent and polypropylene fiber have little difference in improving crack-resistance capability compared with singledoped ones,