混杂纤维混凝土早龄期抗裂性能试验研究

选取强度等级CF40和CF50混凝土,在混杂纤维混凝土配合比三元叠加法试验基础上确定配合比:在钢纤维体积分数固定为1%时,聚丙烯纤维掺量在0.3～1.5 kg/m3内按级差0.3 kg/m3取5个水平;在聚丙烯纤维掺量为0.9 kg/m3时,钢纤维体积分数在0.5%～2.0%内按级差0.5%取4个水平,研究纤维的不同掺量对混凝土早龄期抗裂性能的影响以及试件裂缝形态的变化.结果表明,钢-聚丙烯纤维混杂具有耦合提高混凝土早龄期抗裂性能的作用,早龄期抗裂性能随纤维掺量的增加而提高;钢纤维体积分数和聚丙烯纤维掺量存在合理有效值.纤维混杂可以协同阻裂和限裂,使混凝土裂缝由宽、长形态调整为细、短形态.

Experimental Research of Crack Resistance of Hybrid Fiber Reinforced Concrete at Early Age

The mix proportions of hybrid fiber reinforced concrete with strength grades of CF40 and CF50 were designed according to the superposition mix design method,in which five levels of the polypropylene fiber content were selected in the range from 0.3 kg/m3 to 1.5 kg/m3 with the increment of 0.3 kg/m3 as the volume fraction of steel fiber was constant at 1.0%,and four levels of volume fraction of steel fiber were chosen in the range from 0.5% to 2.0% with the increment of 0.5% as the content of polypropylene fiber was kept in 0.9 kg/m3.The effects of different contents of fiber on the crack resistance of concrete at early age and the crack states variation of specimens were studied.The results showed that the hybrid of steel fiber and polypropylene fiber had coupling effects on improving the crack resistance of concrete at early age,and the crack resistance raised with the increase of fiber contents.The results also indicated that there were the rational and effective values of the volume fraction of steel fiber and the content of polypropylene fiber,and the fiber hybrid could collaboratively prevent and limit the cracks,which made thin and short cracks change into wide and long shape.