New Deveopments in Shrinkage-Reducing Admixtures

N. Berke, P. DallaireMichael, M. Hicks, A. Kerkar
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引用次数: 26

Abstract

Concrete is one of the most widely used construction materials in the world. In applications where appearance, durability, and permeability are of concern, reduction of cracking is a key need. A common cause of cracking is restrained drying shrinkage. Until very recently, drying shrinkage cracking has been controlled by reducing joint spacing, increasing reinforcement, and using expansive cements and admixtures. In this paper a new shrinkage-reducing admixture (SRA) is discussed. SRAs provide a convenient means of reducing drying as they are added during batching and mix easily into the concrete, The SRA material discussed in this paper improved workability and finishing as an added benefit. The effects of mixture proportioning, curing conditions, and SRA content on the long-term drying shrinkage reductions of 50% can be achieved, and that there is a significant improvement in restrained shrinkage performance. Even though the lowest absolute values for drying shrinkage occur with proper curing, there is still a substantial reduction in drying shrinkage for specimens cured for short times. It is shown that shrinkage reduction is directly related to the SRA addition rate as a percentage of the mixing water. Furthermore, data on large-scale field experiments show that substantial reduction in cracking is obtained for concretes treated with SRA.
减缩外加剂的新进展
混凝土是世界上应用最广泛的建筑材料之一。在外观、耐用性和渗透性方面的应用中,减少开裂是一个关键的需求。开裂的一个常见原因是干燥收缩受限。直到最近,干燥收缩开裂一直是通过减小接缝间距、增加钢筋和使用膨胀水泥和外加剂来控制的。本文讨论了一种新型的减缩掺合料(SRA)。SRA提供了一种方便的减少干燥的方法,因为它们是在配料时添加的,并且很容易混合到混凝土中。本文讨论的SRA材料提高了和易性和精加工,这是一个额外的好处。混合料配比、养护条件和SRA含量对长期干燥收缩率的影响可达到50%,抑制收缩性能有明显改善。尽管干燥收缩率的绝对值在适当的养护下是最低的,但对于短时间养护的试样,干燥收缩率仍然有很大的降低。结果表明,缩水率的降低与SRA的加入率(占混合水的百分比)直接相关。此外,大型现场试验数据表明,经SRA处理的混凝土裂缝显著减少。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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