Control of Plastic Shrinkage Cracking of Concrete with Fibers

纤维混凝土塑性收缩裂缝的控制

• 批准号: 9908308
• 负责人: Antoine Naaman
• 金额: $ 21.45万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-10-01 至 2003-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9908308&HistoricalAwards=false
• 关键词: Control; Plastic; Shrinkage; Cracking; Concrete

CONTROL OF PLASTIC SHRINKAGE CRACKING OF CONCRETEWITH FIBERSAntoine E. NaamanUniversity of Michigan, Ann ArborProject Summary:The largest single application of synthetic fibers in concrete is in the~control of plastic shrinkage cracking which occurs during the first twenty four hours of age, mostly in slabs and similar restrained structures, while the concrete is still plastic or semi-plastic and before it has attained any significant strength. While numerous studies have dealt with prediction models for the tensile, bending, and fracture properties of fiber reinforced concrete, there is so far no "theoretical" explanation on why a small amount (0.1% to 0.3% by volume) of fine fibers helps control plastic shrinkage cracking in concrete. This study offers to provide a rational answer. An extensive experimental program is proposed and a limited analytical program suggested. The main objectives are: 1) to evaluate the effect of a number of fibers, covering a wide range of properties, on the plastic shrinkage cracking characteristics of concrete; 2) to understand the basic mechanisms by which fibers control plastic shrinkage cracking; 3) to develop an analytical model accounting for such mechanisms; 4) to carry out a parametric evaluation of the effectiveness of various fibers and fiber parameters; 5) to provide some recommendations on the most desirable fiber properties; and, 6) to recommend, for a given fiber, the minimum volume fraction of fibers needed to effectively control plastic shrinkage cracking under most adverse conditions. The results will help compare fiber properties and parameters that are important for control of plastic shrinkage cracking with those properties that are important for improving the mechanical properties of the composite. This study is expected to have a significant economic impact on the future use of fibers, particularly synthetic types, in concrete.

纤维混凝土塑性收缩裂缝的控制。合成纤维在混凝土中最大的单一应用是控制塑性收缩裂缝，这种裂缝发生在混凝土龄期的前24小时，主要是在板和类似的约束结构中，而混凝土仍然是塑性或半塑性的，并且在它达到任何显著的强度之前。虽然许多研究已经处理了纤维增强混凝土的拉伸，弯曲和断裂性能的预测模型，但到目前为止，还没有“理论”解释为什么少量（0.1%至0.3%体积）的细纤维有助于控制混凝土中的塑性收缩开裂。这项研究提供了一个合理的答案。提出了一个广泛的实验方案和有限的分析程序建议。主要目标是：1）评估多种纤维对混凝土塑性收缩开裂特性的影响，包括广泛的性能范围; 2）理解纤维控制塑性收缩开裂的基本机理; 3）开发解释这种机理的分析模型; 4）对各种纤维和纤维参数的有效性进行参数评估; 5）提供关于最理想的纤维性能的一些建议;和6）对于给定的纤维，建议在最不利的条件下有效控制塑性收缩开裂所需的纤维的最小体积分数。这些结果将有助于比较纤维的性能和参数，是重要的塑性收缩开裂的控制与那些性能，是重要的改善复合材料的机械性能。这项研究预计将对未来在混凝土中使用纤维，特别是合成纤维产生重大的经济影响。