Durability and Pore Structure of Concrete subject to Repeated Load

(1)对混凝土和砂浆试件进行了不同应力水平下的疲劳试验。结果表明，应力水平的升高会加速材料的疲劳断裂。进一步进行了应力水平低于疲劳破裂水平的疲劳试验，并提出了用Gompertz曲线上的尺度来表示试件的疲劳程度。(2)对于1、28、90天的水浸养护和7天的密封养护等早期养护条件的影响，明确了养护不足易导致疲劳抗力下降。(3)声发射观测表明，疲劳破裂存在疲劳起始阶段、疲劳逐渐积累阶段和疲劳快速进展的最后阶段三个阶段。(4)采用压汞技术对疲劳试样的孔隙结构进行了研究，发现随着疲劳的进行，试样的孔隙体积逐渐增大。(5)随着疲劳的进展，固化不良的试件的碳化率也随之加快。认为这是由于毛细孔体积增大所致。

(1) Fatigue tests of concrete and mortar specimens were carried out at various levels of stresses. The rise of the stress level was found out to accelerate fatigue rupture of them. The further fatigue tests that the stress levels are lower than the ones of fatigue rupture were conducted, and the scale on the Gompertz curve was proposed for expressing the degree of fatigue of specimens.(2) As for the effect of curing conditions in early ages, such as water immersed cures of 1, 28, 90days and sealed cure of 7 days, it was made clear that insufficient cure is susceptible to decrease of fatigue resistance.(3) Acoustic emission observation made clear that the existence of the three stages to fatigue rupture such as the initiation stage of fatigue, the gradually accumulated stage of fatigue and the last stage of rapidly progressing fatigue.(4) Pore structures of the specimens fatigued were investigated by the mercury-intrusion technique, it was found out that the pore volumes of them increased according with the progress of fatigue.(5) Carbonation rate that is an index of durability was also accelerated for the specimens of poorly cured according with progress of fatigue. It is considered due to the increase of pore volume of capillary size.