粉煤灰对改善混凝土碱-骨料反应的试验研究

碱-骨料可导致混凝土开裂甚至损毁,这是水利工程常见的破坏现象。文章采用岩相法、砂浆棒快速法研究了粉煤灰对改善混凝土碱-骨料反应的性能。结果表明:23组粗细骨料中有8组存在潜在碱活性危害,不掺粉煤灰的试件,碱-骨料反应明显,混凝土膨胀率呈指数型变化,掺20%粉煤灰试件膨胀率变化较小,粉煤灰对骨料的碱活性具有明显的抑制作用。为防止混凝土建筑物遭受碱-骨料反应破坏,建议在工程中使用碱含量较低的水泥,同时,在保证强度和耐久性的前提下掺入20%及以上的粉煤灰能够有效控制混凝土发生碱-骨料反应。

Experimental Study on Improving Alkali-aggregate Reaction of Concrete with Fly Ash

Alkali-aggregate can lead to concrete cracking and even damage,which is a common destruction phenomenon in water conservancy projects.The performance of fly ash in improving alkali-aggregate reaction of concrete is studied by lithofacies method and Accelerating Mortar-bar method in the paper.The results show that 8 of the 23 groups of coarse and fine aggregate have the potential harm of alkali activity.The samples without fly ash have prominent alkali-aggregate reaction,the concrete expansion rate is changed exponentially,and the expansion rate of the samples with 20%fly ash is slightly changed.The fly ash has obvious inhibitory effect on the alkali activity of the aggregate.It is suggested to use cement with low alkali-content in the project in order to prevent concrete buildings from being damaged by alkali-aggregate reaction.Meanwhile,the alkali-aggregate reaction of concrete can be effectively controlled by adding fly ash of 20%or more on the premise of ensuring strength and durability.