纤维自密实混凝土早期收缩及阻裂特性研究

Study on Early-age Shrinkage and Crack Resistance of Fiber Reinforced Self-compacting Concrete

采用非接触收缩变形试验、平板抗裂试验以及三点弯曲梁声发射检测,研究了掺PVA纤维、钢纤维以及两者混杂自密实混凝土(SCC)的早期塑性收缩、约束收缩以及荷载作用下的阻裂特性。结果表明,所掺的PVA纤维对改善SCC早期自由收缩作用有限,但能够抑制约束条件下基体的开裂;体积掺量分别为0.07%和1.0%的PVA纤维与钢纤维混杂后,对降低SCC早期收缩开裂效果显著,所配制的SCC抗裂性达到Ⅰ级标准;PVA纤维可闭合加载初期SCC基体中的微裂缝,钢纤维则能有效阻止加载中期裂缝的衍生和扩展,由于两种纤维的协同阻裂作用,能够有效改善SCC的断裂韧性。

Using the non-contact shrinkage measuresed tests,flat tests and three points bending beam acoustic emission tests, the early age plastic shrinkage, restrained shrinkage and crack resistance characteristics under load of PVA fiber,steel fiber and hybrid fiber reinforced SCC were studied. Results show that,PVA fiber mixed to improve the effect of early free volume shrinkage for SCC is limited,but can inhibit the cracking in the constraint matrixies; as for volume fractions of PVA fiber and steel fiber are respectively 0. 07% and 1% mixed,significantly reduce early cracking of SCC,and the crack resistance of concrete reaches gradeⅠ standard. PVA fiber can close micro-cracks in matrix at the initial load,and steel fiber can effectively prevent cracks deriving and extending during mid-load,Because of the two kinds of fiber synergistic anti-crack effect,which can effectively improve the fracture toughness of self compacting concrete.