预吸水轻骨料对高强混凝土早期收缩的影响

Influence of Pre-wetted Lightweight Aggregate on Early-age Shrinkage of High Strength Concrete

基于等强度原则,设计了内养护水灰比分别为0、0.04、0.08和0.12的4组高强混凝土,研究了密封和干燥两种养护条件下,预吸水轻骨料的体积掺量对混凝土早龄期自由收缩、内部湿度及弹性模量的影响。结果表明:随着内养护水引入量的增大,28d龄期内高强混凝土内部湿度下降和早期总收缩变形均得到明显缓解,且对密封养护混凝土的影响更明显;但混凝土的弹性模量随轻骨料掺量增大而下降,应用中应优化选择预吸水轻骨料的掺量。在干燥环境条件下,轻骨料预吸水内养护法并不能根除干燥收缩,内养护高强混凝土中可能存在较大的内部湿度梯度及近表面干燥现象。

Influence of substituting volume fraction of pre-wetted light weight aggregate （LWA） on the early-age free shrinkage, internal relative humidity and elastic modulus of four high strength concrete （HSC）, with induced curing water to cement ratios of 0, 0.04, 0.08, 0.12 and with a similar compressive strength, under plastic film sealing and environmental drying was investigated. The internal humidity reduction and total free shrinkage of internal-cured concrete （IC） within 28 days were mitigated when the amount of induced curing water was increased, especially for the case of sealed specimens. On the contrary, the elastic modulus of IC decreases with the increase of substituting volume fraction of pre-wetted LWA. Therefore an optimized amount of induced curing water needs to be considered in practical application. Furthermore, in the case of drying environment, drying shrinkage of HSC can not be fully eliminated by internal curing with pre-wetted LWA. Relative remarkable humidity gradient and near-surface drying phenomenon could exist.