Durability and Pore Structure of Concrete subject to Repeated Load

(1)进行了混凝土和砂浆试件在不同应力水平下的疲劳试验。结果表明，应力水平的升高加速了疲劳断裂。进一步进行了应力水平低于疲劳断裂应力水平的疲劳试验，提出了用Gompertz曲线上的标度来表示试件的疲劳程度。(2)对于早期养护条件的影响，如1、28、90天的水浸养护和7天的密封养护，表明固化不足易导致疲劳抗力的降低。(3)声发射观测表明，疲劳断裂的三个阶段的存在，如疲劳的起始阶段，(4)用压汞法研究疲劳后试件的孔结构，发现其孔体积随疲劳的发展而增大。(5)碳化速率是耐久性的一个指标，随疲劳的发展而加快。认为这是由于毛细管径的孔体积增大所致。

(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.