Influence of Curing Method on Strength Development of Concrete Using Fly Ash

随着近年来提倡循环利用的社会环境的不断进步，粉煤灰在建筑建设中的使用量越来越大。然而，除了早期湿养护外，粉煤灰混凝土的积累资料很少。为阐明早期养护条件对钢筋混凝土建筑结构含粉煤灰混凝土中长期强度发展的影响，本研究通过试验研究了含粉煤灰混凝土早期养护过程中不同水分条件对其中长期强度发展的影响，考察了粉煤灰对强度、k值的贡献与粉煤灰质量、混凝土配合比的关系。并通过分析养护条件。(1)试验了粉煤灰k在不同条件下对高强和中强混凝土的强度贡献，并考察了k与初始养护条件类型和养护周期的关系。阐明了养护条件对k的影响。(2)收集了以往粉煤灰混凝土强度试验数据。在整理数据的基础上，考察了k与粉煤灰Blaine比表面积、掺量与水泥掺量、硅酸盐水泥与粉煤灰掺量比（C/Fa）、养护条件之间的关系。结果表明：粉煤灰Blaine比表面积越大，k值越高。k随C/Fa的增加而增加。长期龄期密封养护的K值约为标准养护的80%，空气养护的K值约为标准养护的40-50%。(3)含粉煤灰砂浆的强度表达式可以用不含粉煤灰砂浆的强度与粉煤灰的火山灰反应和粉煤灰的粉化效应引起的强度增加之和来表示。

With the recent progress of the social environment promoting recycling, it is required that the use for fly ash be increased in building construction. However, there is few data on fly ash concrete accumulated in except those be moist cured at early age. To elucidate the effects of early curing conditions on the mid-and long-term strength development of concrete containing fly ash for reinforced concrete building structures, this study investigated the effects of various moisture conditions during early curing of concrete containing fly ash on its mid-and long-term strength development by experiments, and examined the relationship between the contributions of fly ash to strength, k, and fly ash qualities, concrete mixture proportions, and curing conditions by analyses. The following results are made :(1)The strength contributions of fly ash, k, under various conditions in high-strength and normal-strength concrete were experimented, and the relationships between k and initial curing condition type and curing period were examined. As a result, the influence of curing condition on k was clarified.(2)The past experiment data on strength of fly ash concrete were collected. Based on the organized data, the relationships between k and Blaine specific surface area of fly ash, portiand cement content, content ratio of portland cement and fly ash (C/Fa) and curing condition were examined. The following observations were made : the bigger Blaine specific surface area of fly ash is, the higher k is. k at long-term ages tends to increase as C/Fa increases. k at long-term ages by sealed curing are about 80% times as large as those by standard curing, and k by air curing are about 40-50% times as large as those by standard curing.(3)The strength expression of mortar containing fly ash could be expressed by the summation of the strength of mortar without fly ash and the strength increase due to pozzoknic reaction of fly ash and the powder effect of fly ash.