The Use of Synthetic Blended Fibers to Reduce Cracking Risk in High Performance Concrete
The Use of Synthetic Blended Fibers to Reduce Cracking Risk in High Performance Concrete
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使用合成混合纤维降低高性能混凝土的开裂风险
DOI：
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发表时间：
2014
期刊：
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通讯作者：
J. Bañuelos
中科院分区：
文献类型：
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作者：
J. Ideker;J. Bañuelos
交通部门已经观察到他们的混凝土结构存在不同程度的裂缝。高性能钢筋混凝土结构的开裂，特别是桥面开裂，是太平洋西北交通部最关心的问题。早期开裂(特别是在安置后的第一年内)会导致额外的成本，并给俄勒冈州交通部(ODOT)带来巨大的维护负担。高性能混凝土裂缝背后的原因是众所周知的，并在现有的文献中记录在案。俄勒冈州立大学最近在两个独立项目：SPR 711和SPR 728下进行的研究阐明了主要用于混凝土桥面的高性能混凝土混合料的收缩倾向。这些以前的项目确定了1)减少收缩的缓解方法(例如，使用细轻集料的内部养护(FLWA)和/或使用减缩剂(SRA))，以及2)提出了收缩测量技术和使用这些技术的阈值/限制，这些技术应该减少收缩和早期裂缝风险。该项目的目的是研究一种相对较新的控制早期裂缝的技术；在高性能混凝土混合料中使用混合浆料聚丙烯纤维。这项工作的主要发现是，单独使用干燥收缩测试方法，而没有捕获开裂风险，表明纤维的加入并不能减少无约束试件的干燥收缩。然而，在约束试验中(促进裂纹形成的可能性)，纤维能够1)减少试件中的应力产生速率，2)延长约束环试验(ASTM C 1581)中的裂纹产生时间，以及3)一旦裂纹开始产生，就减少了裂纹宽度和裂纹的扩展。因此，在高性能混凝土中使用混合纤维为降低使用中的裂缝风险提供了另一种可行的解决方案。
Transportation departments have observed varying degrees of cracking in their concrete structures. Cracking of high performance reinforced concrete structures, in particular bridge decks, is of paramount concern to Pacific Northwest Departments of Transportation. Cracking at early ages (especially within the first year after placement) results in additional costs and a significant maintenance burden to Oregon Department of Transportation (ODOT). The causes behind cracking in high performance concrete are well known and documented in the existing literature. Recent research at Oregon State University under two separate projects: SPR 711 and SPR 728 has elucidated the propensity for shrinkage in high performance concrete mixtures mainly used for concrete bridge decks. These previous projects identified 1) mitigation methods to reduce shrinkage (e.g. internal curing using fine lightweight aggregates (FLWA), and/or the use of shrinkage reducing admixtures (SRA)) and 2) proposed shrinkage measurement techniques and thresholds/limits using those techniques that should reduce shrinkage and early-age cracking risk. The aim of this project was to investigate a relatively new technique to control early-age cracking; the use of blended size polypropylene fibers in high performance concrete mixtures. The key findings from this work were that the use of drying shrinkage test methods alone, without the capture of cracking risk, showed that the inclusion of fibers did not reduce drying shrinkage in unrestrained specimens. However, in restrained testing (where the possibility of crack formation is promoted) the fibers were able to 1) reduce the rate of stress generation in specimens 2) prolong the time to cracking in the restrained ring test (ASTM C 1581) and 3) reduce the crack widths and the growth of cracks once cracking did initiate. As a result the use of blended fibers in high performance concrete points to another viable solution for reducing the risk of cracking in service.