碳化作用下轻骨料混凝土干缩变形及影响规律

采用碳化试验和干燥收缩试验相结合,研究了轻骨料混凝土在碳化作用下的干缩变形发展规律及其影响因素。结果表明,加速碳化作用下,轻骨料混凝土的干缩变形显著增长,而随着矿物掺合料的掺入,干缩率得到一定程度的抑制,其中掺超细粉煤灰轻骨料混凝土碳化干缩率最小;骨料预湿完全条件下轻骨料混凝土水胶比越大,碳化干缩变形越大;轻骨料混凝土在高浓度CO2加速碳化作用下干缩变形显著高于自然碳化混凝土;而在相对湿度50%条件下碳化时,其干缩率要大于其它湿度条件下的试样;另外,轻骨料预湿后混凝土碳化干缩率要低于未预湿轻骨料混凝土。因此,在实际工程中,选择合适的矿物掺合料、水胶比、养护条件以及骨料的预湿工艺对轻骨料混凝土的减缩防裂具有较好的效果。

Influence Laws and Dry Shrinkage of Lightweight Aggregate Concrete under the Carbonization

The developing laws and influence factors of the dry shrinkage of lightweight aggregate concrete under the carbonization were researched by carbonization test and dry shrinkage test.The results indicated that the dry shrinkage of lightweight aggregate concrete increased significantly under the accelerated carbonation,while the dry shrinkage is inhibited to some extent with the addition of mineral admixture,and the lightweight aggregate concrete containing ultra-fine fly ash has the least dry shrinkage.After lightweight aggregate pre-soaked,the higher water-binder ratio is,the more dry shrinkage after carbonization will be.And the dry shrinkage of lightweight aggregate concrete in high concentration carbon dioxide environment is significantly higher than that of concrete in natural carbonization environment.When the relative humidity of carbonization environment is 50%,the dry shrinkage of lightweight aggregate reaches the maximum.Moreover,the dry shrinkage of concrete after lightweight aggregate pre-soaked is lower than that of not pre-soaked lightweight aggregate concrete.Therefore,in practical engineering,selecting the appropriate mineral admixture,water-binder ratio,curing condition and lightweight aggregate pre-soaked technology have the better effect on the shrinkage reducing and crack preventing of lightweight aggregate concrete.