混凝土的早期收缩机理与开裂条件研究

对混凝土收缩的研究进行了总结,并在此基础上对混凝土产生收缩的机理进行了深入探讨。混凝土产生收缩的原因是由于自干燥导致的弯液面曲率半径的减小和表面张力的提高。混凝土在发生开裂时的拉应力小于当时混凝土的劈裂抗拉强度。环形约束时,当拉应力达到劈裂抗拉强度的55%~62%时,混凝土发生开裂。试验室中可以根据约束混凝土拉应力的发展趋势和开裂的时间来预测工程中混凝土发生开裂的可能性。

MECHANISM OF EARLY AGE SHRINKAGE AND CRACKING CONDITION OF CONCRETE

The research works on shrinkage of concrete was reviewed, on the basis of which shrinkage mechanism was discussed in depth. The cause of autogenous shrinkage is the decrease of the radius of curvature and the increase of surface tension of water, which is because of the self-desiccation of cement paste. The tensile stress of concrete at cracking is lower than the tensile strength. Under ring restrained condition, cracking occurs when the stress level reaches 55%-62% of splitting tensile strength. Cracking possibility could be predicted in the lab according to the stress level development and the age at cracking under restrained condition.