混凝土界面区组分梯度分布的改善及其对混凝土性能影响

【作者】 董延玲；

【导师】 杨久俊；

【作者基本信息】 郑州大学 ， 材料学， 2004， 硕士

【摘要】 梯度功能材料（FGM）是指在材料设计制造过程中，使构成材料的要素沿着厚度方向由一侧到另一侧呈梯度连续变化，内部没有明显的界面，并使材料的性能与功能呈现连续梯度变化的一种新型材料，其优越的性能，已在航天、能源、电子、化学和生物医学等工程领域展示了诱人的应用前景；分形理论则为定量描述许多不规则，复杂的，具有自相似质的研究客体提供了一种有力的工具。 本文把FGM的概念引入到混凝土中的骨料—水泥石界面区，采用化学的办法对骨料进行预处理，实现了骨料表面的粗糙化和活化，从而造成骨料和水泥浆体的相互交叉梯度分布，使界面弱区得到了强化，缓和了界面应力，进而提高了水泥基材料的宏观力学性能。同时本文引用分形理论，用分数维对骨料表面粗糙度进行了量化表征，初步建立骨料表面分形维数和混凝土界面粘结强度及抗压强度的关系。通过试验与分析，本文得到以下明确结果： 1、经预处理的骨料表面特性有了明显变化：结果表明，经酸处理的骨料表面均不同程度的粗糙化、洁净化并具有一定的活性，可在一定程度上与水泥浆反应形成水化产物而增强界面结合；但经NaOH（碱）处理的骨料，因骨料表面附着有硅酸钠酸性物质，且碱性表面更有利于大晶粒的形成，也有使水泥水化产物在骨料表面快速结晶凝结的作用，而使界面区结构向内应力增大、结构疏松等不利的方向发展； 2、酸处理骨料配制的混凝土的界面区结构有了明显改善，形成了良好的组分梯度分布形态：从界面区轮廓图来看，骨料未经处理的界面区轮廓线较为平滑，而骨料经酸处理过的界面区轮廓线则变得较为曲折，表明通过对骨料粗糙化确实造成了界面区骨料和水泥浆体的相互交叉梯度分布；从界面区成分分析来看，所作的点扫描和面扫描都表明AL、Si等元素呈现很好的梯度交叉分布；从形貌图来看，和骨料未经处理的界面区相比，骨料用酸处理的界面区界面结合较好，没有裂纹形成，也朱见CH大晶粒和大的Aft大晶粒。大晶粒明显减少，晶粒细化，C-S-H凝胶增多，孔隙减少，界面区结构致密化。 3、由于界面性质的改善而带来了混凝土强度的显著提高和综合力学行为的改善：其中经H₃PO₁处理15min的骨料与水泥浆的28天界面粘结强度抗压强度分别提高51％和32％；经H₂SO₁处理15min的骨料与水泥浆的28天界面粘结强度和郑州大学硕士毕业论文抗压强度分别提46%和30%;经HF处理18Omin卵石混凝土抗压强度提高26%。同时混凝土的韧性得到一定程度的提高，弹性变形增加，弹性变形与最大荷载处总变形比提高，所有这些都有利于混凝土总体性能的高效发挥。 4、基本建立了骨料表面分形维数与骨料一水泥石粘结强度及抗压强度之间的数学关系:本文初步建立的骨料表面分形维数和骨料一水泥石粘结强度及混凝土抗压强度关系式，关系式表明粘结强度和抗压强度都随分数维的增加而增大，且通过对两者的相关性分析，表明其相关性是显著的。 本文研究表明，采用对骨料进行化学处理的办法来改善水泥石一骨料界面区确实带来界面区组分和结构的梯度变化，造成粗糙表面与浆体良好的梯度分布与良好的藕合，缓和了界面应力，从而使水泥基材料的宏观力学性能得到提高。通过对骨料的处理来对界面区不良的梯度结构进行改善极有可能为水泥基材料的改性与拓宽用途带来希望。更多还原

【Abstract】 Functionally Gradient Material (FGM) is that the components and the structure of the material are gradient distribution from one side of the material to the other, which has been used in the fields of space industry, nuclear industry, energy industry, electron industry and the bioengineering. Fractal theory provides a useful tool to describe many irregular, complex, self-alike study objects in numerical quantities, up to now, which has been one of hotspots in the field of math, physics, chemistry, seismology, material science.In this paper, the concept of FGM was introduced into aggregate-cement paste interfacial zone in concrete .Through the pretreatment of aggregate, aggregates get roughness , cleaner and be of some active , which results in the aggregate and cement paste components display crossed and gradient distribution in interfacial zone and the interface weak zone is enhanced and interfacial inner stress is released. All these bring the improvement of the physical and mechanical properties of cement-based material. Meanwhile, the relations between the fractal dimension of aggregate surface character and bonding strength of interface, compressive strength of concrete are built. The experiment and analysis results indicate that:1 The surface character of pretreated aggregates are markedly changed : the surfaces of aggregates pretreatod by different acids gets roughness , cleaner and be of some active, then can react with cement paste and form hydrated product to rength inter facial linking. However, structure gets looser due to Na2SiO3 gel created on aggregates which easily results in the form of big crystals.2 The structure of ir.terfacial zones between the aggregates pretreated by acids and paste are improved and better gradient distribution of components is formed in it: the skeleton map of theinterface created by un-pretreated aggregates is smooth relatively and the one of the interface created by aggregates pretreated by acids gets more devious .which shows components and structure in the interface form a gradient distribution for a certainty due to aggregate roughness; from analysis of components in the interface , dot SEM and surface SEM both show a better gradient distribution of AK Si etc. elements. Compared with the one created by un-pretreated aggregates ,the linking of the interface created by aggregates pretreated by acids is better, meanwhile no cracks is formed , no big CH crystal and big Aft crystals are seen , the content of OS-H gel increases and holes decrease .3, As a result of the improvement of interface, the mechanical properties of concrete is markedly improved: the bonding strengths between cement paste and aggregate pretreated by H3PO4 and H2SO4 are increased 51% and 46% respectively; the compressive strengths of concrete prepared with aggregate pretreated by H3PO4, H2SO4 and HF are increased 32%, 30% and 26% respectively. Meanwhile, toughness and elastic deformation of concrete are slightly increased.1 > The numeric relations between fractal dimension of aggregate surface and the bonding strength , compressive strength are primarily built: the numeric function show the bonding strength and the compressive strength both raise with the raise of fractal dimension, and the relativity coefficient between fractal dimension of aggregate surface andbonding strength .compressive strength show the relativity is marked.The study shows that the chemical pretreatment of aggregate methodthrough which to improve aggregate-cement paste interfacial zone throwslight on the advance of cement-based materials’ mechanical properties.更多还原