Crack Mitigation Effects of Shrinkage Reducing Admixtures

A. Bentur, M. Berke, T. Durning
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引用次数: 11

Abstract

Shrinkage reducing admixtures (SRA's) are a new type of admixtures, which are effective in reducing the drying shrinkage of concrete. SRA performance has typically been evaluated on the basis of unrestrained drying shrinkage tests. However, it is usually the cracking performance of concrete when shrinkage is restrained that is of primary interest to the marketplace. The current paper presents an evaluation of SRA's based on several parameters: free shrinkage, tensile stresses which develop in a uniaxially restrained rig, and the sensitivity to cracking in such conditions. The positive influence of SRA's on all of these three parameters is demonstrated. A comparison is made between the effect of SRA and of low-volume, polypropylene fiber reinforcement. The latter is known to be effective in controlling early age plastic shrinkage cracking. The present data show that in the case of hardened concrete, after one day of curing, low volumes of fibers do not give any advantage, and it is in this range where the SRA is effective. Thus, the two types of additives can complement each other: the fibers are efficient in controlling plastic shrinkage cracking while the SRA can take over the role of crack control in the hardened concrete, where low volume-low modulus fibers are not effective.
减缩外加剂的减裂效果
减缩掺合料(SRA's)是一种能有效降低混凝土干缩的新型掺合料。SRA性能通常是在无约束干燥收缩试验的基础上进行评估的。然而,它通常是混凝土的开裂性能,当收缩被限制,是主要的兴趣市场。本文提出了基于几个参数的SRA的评估:自由收缩,在单轴约束钻机中产生的拉应力,以及在这种条件下对开裂的敏感性。SRA对这三个参数都有积极的影响。对SRA与小体积聚丙烯纤维增强的效果进行了比较。后者被认为是有效的控制早期塑性收缩开裂。目前的数据表明,在硬化混凝土的情况下,养护一天后,低体积的纤维没有任何优势,它是在这个范围内的SRA是有效的。因此,两种类型的添加剂可以相互补充,纤维在控制塑性收缩开裂方面是有效的,而SRA在硬化混凝土中可以接管裂缝控制的作用,而低体积低模量纤维则不起作用。
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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