摘要
纤维增强水泥基复合材料(Fibers reinforced cementitious composites,FRCC)具有优异的抗拉、抗弯、耐久性等硬化性能,因此被广泛应用于道路、桥梁等建筑工程中。但纤维的存在常导致材料在拌合状态下无法良好成型,进而导致其力学性能劣化。为了优化拌合物性能,其流动性与流变性受到了人们的广泛关注。传统的流动性试验能够快速检验拌合物是否达到了成型要求,但存在人工误差并且测试范围有限;而流变试验则能反映出拌合物在剪切应力条件下材料各组分之间的相互作用,但难以应用于工程。两种试验各有利弊,但互为补充。因此,建立拌合物流动性与流变性之间的关系成为研究水泥基材料拌合性能的必然趋势。为了分析二者的关系,流动性能与流变性能的机理分析是必要的。在实验设计中,研究者们通常采用的手段是对材料的组分进行调整,宏观调控基准配合比或者改变纤维参数,通过对比各因素下拌合物的流动参数及流变参数,或结合硬化材料的微观结构,最终得到拌合性能与硬化性能俱佳的最优化配比。在这一过程中,可获得流动参数与流变参数的变化规律,由数学拟合或者分析模型则可以得到二者关系式。水泥基材料最初的流动-流变关系式由此得来。然而,这种传统分析方法的适用性受到外加剂、材料品种、分析模型等多方面差异的影响,其关系式的物理意义及适用性都是模糊不清的。由于高性能纤维水泥基材料逐渐成为研究对象,低水胶比的设计要求必然导致减水剂的大量使用,多种矿物外加剂的复掺也会改变基体的内部结构,使分析环境更为复杂。此外,关系式的建立依赖于流变分析模型,不同的纤维水泥基材料对应的流变模型也可能不同,这些因素都导致传统的流动-流变关系式无法应用于新型的、掺有纤维的水泥基材料。为了减少因素变化给关系式带来的影响,基于材料自身性质的分析方法是可取的。以材料固有属性为参数建立关系式,试验数据仅作为验证,最终得到的关系式不以试验条件为转移,具有更广泛的适用性与可靠性。本文通过综述FRCC拌合物性能的研究进展,分析了不同纤维因素和基体因素对FRCC拌合物性能的影响方式,探讨了FRCC拌合物的流动性与流变性的关系,指出了现阶段对FRCC拌合物性能研究的不足,为以多尺度混杂纤维增强水泥基材料(Hybrid fibers reinforced cementitious composites,HyFRCC)为代表的新型FRCC的拌合物性能研究提供参考。
Fibers reinforced cementitious composites are widely used in roads,bridges and other construction projects because they have excellent har-dened state properties,including stretching,bending and durability.Nevertheless,cementitious materials can hardly be well formed in the mixing state with the presence of fibers,which would deteriorate the properties of their hardened state.For the sake of optimizing the performance of mixtures,more and more efforts have been paid into the research on the flowability and rheological properties.Traditional flowability test is capable of determining whether the mixtures meet the molding requirements in a short period of time,but it suffers from manual errors and limited test range.The rheological test can reflect the interaction among the components of the mixtures under shear stress,yet it is difficult to be applied in practical projects.There are pros and cons in both test,but they can complement each other.Consequently,it is an inevitable trend to establish the relationship between the flowability and rheological properties of cement-based materials.Aiming at analyzing the relationship between flowability and rheological properties,it is necessary to figure out the mechanism of them.In the experimental design,common approaches adopted by researchers include adjusting the composition of the material,regulating the proportion of components or changing the fiber parameters.The optimal ratio with better fresh performance and hardening performance can be acquired by comparing the flowability and rheological parameters of the mixtures under various factors and observing the microstructure of the hardened materials.In addition,the variation of flowability and rheological parameters can be found out in this process,and the relationship between them can be further obtained by mathematical fitting or analysis model.As a results,the initial flowability-rheology equation of cement-based materials emerge.Unfortunately,the applicability of this traditional analytical method is questioned under diverse additives,materials,analysis models and so forth.The physical meaning and applicability of the relationship are ambiguous.As high performance fiber reinforced cement-based materials are increasingly popular and become the research focus,their design requirements of low water-to-binder ratio will inevitably lead to the use of superplasticizer in large amount.At the same time,the mixing of various mineral admixtures will also change the internal structure of the matrix,making the analysis environment get much more complicated.In addition,the establishment of the relationship rests on the rheological models,and the rheological models corresponding to various fiber cement materials may quite different.These factors make the traditional flow-rheological relationship no longer appropriate to describe the new cement-based materials with fibers.In order to reduce the impact of the factors change on the relationship,it is advisable to analyze the material based on its own properties.The relationship established by taking the inherent properties of the material as parameters and using the test data only for verification will not affected by test conditions and exhibits wider applicability and higher reliability.Based on the research progress on fresh FRCC mixtures performance,the effect on the fresh properties of different fiber factors and matrix factors in cement-based materials is analyzed,the relationship between the workability and rheological properties is discussed,and the deficiency of the research on the performance of FRCC mixture at present is pointed out,for the sake of providing the reference for the research of workability and rheological properties on the new FRCC,represented by multi-scale hybrid fiber reinforced cementitious composites(HyFRCC).
作者
司雯
曹明莉
冯嘉琪
SI Wen;CAO Mingli;FENG Jiaqi(School of Civil Engineering,Dalian University of Technology,Dalian 116024)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2019年第5期819-825,共7页
Materials Reports
基金
国家自然科学基金(51678111
51478082)~~
关键词
纤维
流动性
流变性
纤维/基体因素
fiber
flowability
rheological properties
fiber/matrix factors
