【作者】 曹明莉；

【导师】 王立久；

【作者基本信息】 大连理工大学 ， 材料学， 2009， 博士

【摘要】 混凝土材料的使用和研究已有近二百年的历史,随着科研技术的进步,人们总在不断地试图揭示混凝土材料的组分-结构-性能的相关性,其间涌现了大量可贵的研究成果。一方面,混凝土是一种多层次不均质结构的复合材料,它的非均质、非线性、和各向异性的性质,使得混凝土的强度和变形状态十分复杂,进而也导致了对混凝土结构模型研究的困难。诸多的混凝土结构模型研究取得不同成果的同时,往往忽略了混凝土中骨料间不同的空间排布导致不同应力分布这一重要事实。另一方面,混凝土设计理论仍停滞在以水灰比理论为核心的水泥石结构模型。对混凝土材料使用和研究的指导作用存在着历史和学术上局限性。水泥石结构模型混凝土配合比设计,采用单位用水量W、水灰比W/C和砂率S_p作为基本参数,仅以水灰比保证混凝土强度,用水量及砂率的确定只是以拌合物的工作性为目标,从而没有体现混凝土各组分之间的相互作用及对其强度等性能的贡献。根本原因在于:水灰比理论并没有将水泥石与集料之间建立起必然内在联系。随着高强、高性能混凝土的发展,高强度等级的混凝土更加依赖其中粗骨料的骨架强度。传统的水泥石理论已不再适应混凝土的新发展。为此,根据吴中伟院士的大中心质学说思想和结晶学晶体密垛理论,本论文提出混凝土架构模型。认为:混凝土是由粗集料架构、砂浆和界面过渡区组合而成,混凝土的强度来自于三者的贡献。其中粗集料架构是指粗集料的空间搭配型态,相当于人体的“骨架”,它取决于粗集料与水泥、细集料二者的相对量,可以架浆比N参数表征。混凝土中水泥石与细集料构成的砂浆则相当于连接骨骼的“肌肉”,在架构模型中起龛固胶结粗集料架构作用,而其中细集料则类似肌肉中的“纤维”。混凝土性态之所以千差万别,根本原因就在于除了粗集料形成的架构外主要是混凝土中砂浆对水泥标准胶砂的偏离。论文的主要工作和成果包括:1深入分析现有混凝土强度及结构理论的基础上,提出混凝土水泥石三圆模型,并客观指出基于水灰比参数的混凝土水泥石C模型,以及传统混凝土设计理论的局限。基于混凝土水泥石C模型提出了混凝土水泥石J模型。该模型以集浆比J概念,综合考虑集灰比和水灰比对混凝土强度的影响,首次将骨料对混凝土强度的贡献量化,真实地体现了混凝土强度由其中水泥石和骨料共同提供的物理本质。建立的基于集浆比J的水泥石理论数学模型fcu=A_jfce[1/J-B_j],确立以单位用水量W、集浆比J为基本参数的双参数混凝土设计方法。该部分工作补充和完善了混凝土强度及设计理论。2对于混凝土中砂浆的研究,采用DIP图像处理技术,研究其中砂的粒形特征,建立了砂浆偏离函数及砂浆流动性与用水量函数关系,量化了砂的颗粒级配及粒形特征对砂浆性能的影响。为架构模型设计中参数的确定提供依据。相关结论包括:砂灰比函数:(?)偏离函数:(?)砂浆流动性与用水量函数关系:(?)3鉴于混凝土架构模型理论中,粗骨料具有的独特地位和作用,本研究对其架构特性进行了较为深入全面的研究。(1)对真实状态下混凝土内部骨料配位结构的空间配位形式的测定统计及相关计算表明结果:在振捣状态下混凝土试件内部,大多数骨料配位数集中在6～8范围内;并提出了三种架构模型基元;混凝土架构模型单元及其组合的强度测试实验结果验证了混凝土中骨料球分布不同会对混凝土强度造成影响。(2)应用DIP技术,确定粗骨料的粒形参数扁平比和球度为研究对象,进而明确粗骨料粒形特征的的表征,使对粗骨料粒形的研究变得更为便利。通过研究粗骨料的堆垛特性,建立了粗骨料粒形参数与堆积空隙率(亦即填充密实度)函数关系、粒形参数与架构配位数的关系。使得混凝土中粗骨料的研究从定性转化成定量。4架浆比参数作为架构模型的主要参数,突破了水灰比参数的局限,充分体现了骨料(粗骨料)的架构作用;由复合原理推得的架浆比强度公式(?)贴切反映了架构模型中各结构层对强度的贡献。5以架浆比N(或N_c)、砂灰比偏离D_j(或砂浆比S_w)、单位用水量W为基本参数的混凝土架构设计方法的数学模型,明确了架构混凝土设计中各参数的确定方法,以及相应的设计流程。各参数的确定为:(1)架浆比N:(?)(2)偏离函数D_j:(?)(3)单位用水量W:(?)6采用混凝土架构模型设计方法,配制架构混凝土,并考察其力学及耐久性能。(1)对比架构混凝土与传统混凝土的试验结果,表明:单方水泥用量可降低25kg,而其抗压强度仅比传统混凝土降低0.2%,并完全满足设计要求。这说明,相对于传统混凝土,架构混凝土具有更好的经济性。(2)架构混凝土的抗冻耐久性实验结果的因素分析表明:①在一定范围内(1.12-1.34),架浆比越小,混凝土抗冻性越好。②在架构混凝土中掺加粉煤灰和硅灰等掺合料,能够有效提高混凝土的抗冻耐久性,并且掺加硅灰的效果要优于粉煤灰。混凝土架构模型是继水泥石模型理论提出的新的混凝土结构模型研究方法,由于该模型是在能够体现混凝土宏观结构本质的物理模型基础上建立的数学模型,因而能更充分地反映混凝土中各材料组分对混凝土整体性能的真实的贡献。本论文的研究工作,仅仅是为混凝土研究提供一条新思路,尚期待更加深入全面的研究工作,以完善混凝土架构模型理论体系。更多还原

【Abstract】 The use and research of concrete material have nearly 200 years’ history. With the development of scientific research and technology, the components - structure - properties correlation of concrete is constantly to be revealed. During this period, we have gained a large number of valuable research achievements.On the one hand, concrete is a multi-level and non-homogeneous composite material. The non-homogeneous, non-linear, and anisotropic property makes the strength and deformation of concrete is very complex, thus it also leads to difficulties in the reach of concrete structure model. As many of the concrete structure model achieve different results, this important fact that the different space-arranged of the aggregate in concrete leading to different stress distribution is often overlooked.On the other hand, concrete design theory is still stuck in the structure model of cement paste, the core of which is still water-cement ratio theory. It has historical and academic limitations in the use of concrete and research guidance.The cement paste structure model of concrete mix design, using unit of water W, water-cement ratio W/C and the rate of sand Sp as the basic parameters, only water-cement ratio ensuring the strength and using the rate of water and sand as the goal of mix workability, does not reflect the interaction between the various components of concrete and the contribution to their strength. The main reason is: water-cement ratio theory has not established intrinsic link between the cement and aggregates. With the high-strength and high-performance concrete developed, high-strength concrete is dependent much more on strength of coarse aggregate skeleton. Traditional concrete theory is no longer adapted to the new developments.To this end, based on the theory of centroplasm hypothesis proposed by Wu zhongwei academician and the crystal principle, the thesis brings up a model of concrete framework structure. The author believes that the concrete is composed of coarse aggregate framework, mortar and interface transition area. The strength of concrete is from the three contributions. The framework structure is that coarse aggregates arrange in space, just like human being’s skeleton. It depends on the volumetric ratio which is composed of coarse aggregate, cement and fine aggregate, which can be expressed by the rate of framework-mortar N. The mortar which is composed of hardened cement paste and fine aggregate plays a role of adhesive bonding of coarse aggregate in the framework and structure model, as the muscle does in our body. And fine aggregate in mortar plays a role of strengthening the model just like the fiber in muscle. The essential reason why concrete performance varies so much lies on that in addition to the structure formed by coarse aggregate, the major reason is the deviation causing by mortar in concrete and the standard cement mortar.The main work and results of the thesis include:1. Based on the in-depth analysis of existing concrete strength and structure the theory, the hardened cement paste model is proposed, and the C concrete model of the parameters based on water-cement ratio as well as the limitations of traditional concrete design theory is pointed out objectively. The J concrete model is proposed on the base of C concrete model. The model is based on the concept of the aggraegate-paste ratio J, considering the effect on concrete strength of aggregates-cement ratio and water-cement ratio in the whole, the contribution of aggregate on the strength of concrete is quantitative the first time and it truly reflects the physical nature that the strength of concrete which the cement and aggregate provide together. Based on the J parameter and the correlative strength theory formula f_cu=A_j·f_ce[1/J-B_j], unit water dosage W, aggregates-paste ratio J as essential parameters double parameter concrete design method is established. The part of the work supplements and improves the concrete strength and design theory.2. For the study of concrete mortar, the paper researches shape character by digital image processing （DIP method）, sets up mortar deviating function and a function between the mortar slump and water quantity and also quantifies the effect of the aggregate distribution and particle shape characteristics on mortar property. The correlative results are cement-sand ratio function:（?）, and deviating function:（?）, and relationship between the mortar slump and water quantity:3. In view of the theory of concrete structure, the coarse aggregate has aunique status. This paper reaches its structure characteristics on a more in-depth and comprehensive study.（1） For the real state of concrete, the determination statistics of concrete aggregate coordination structure within the space coordinate of the form and the related calculations show that:At the vibrated state in the concrete specimens, the number of most aggregate coordination focus on 6 to 8; three basic unit of framework model are brought forward ; the strength test results of concrete framework structure model unit and compositions validate that the different distribution of the balls in concrete affect the aggregate concrete strength. （2）With the application of DIP techniques, using the sphericity and thickness/breadth ratio as the shaping character parameter, then make the characterization of coarse aggregate grain shape characteristics clear, so that the reach of coarse aggregate grain shape becomes more convenient. By studying the characteristics of coarse aggregate stacking, the function relationship between the coarse aggregate grain shape parameters and accumulation porosity （that is, filling density）, the grain shape parameters and coordination number of framework structure are established, which makes research of the coarse aggregate in concrete from qualitative into quantitative.4. Framework-mortar ratio as the main parameters of the model, breaks through the parameters limitations of water-cement ratio and fully reflects the aggregate （coarse aggregate）framework structure role; the strength formula of framework （?） that is reasoned fromcompound principles, reflecting the various structural layers ’contribution to strength appropriately.5. Establishing the mathematic model of designing metho of framework concrete whichuses framework-mortar ratio N （or N_c）, sand-cement ratio deviation D_j （or S_w）, and unit water dosage W as essential parameters clears the structure of concrete design methods, including the three parameters determination and the relevant design process.The determination method of the various parameters in the design method is: framework-mortar ratio N: （?）, sand-cement ratio deviating function:（?）, and unit water dosage: （?）6. Using framework structure mode design for preparation of framework structure concrete and investigating the property of mechanics and durability.（1）The test results of the framework structure concrete and the traditional concrete indicate that: per cubic amount of cement can be reduced of 25kg, while the compressive strength is only 0.2% lower than traditional concrete, and folly meet the design requirements. At the same time, a comparative test of the concrete durability is made. The results show that properties of resistance to freeze-thaw, resistance to chloride ion permeability and resistance to carbonation can meet the design requirements. This shows that compared with traditional concrete, framework structure concrete is more economy.（2） The experimental results analysis of the resistance to freeze-thaw framework structure concrete shows that: ①Within a certain range （1.12～1.34）, the smaller the framework-mortar ratio is, the better the frost resistance of concrete is. This is because: According to the framework theory, the framework-mortar ratio is larger, indicating that the coarse aggregate is more in concrete, the concrete is denser and the frost resistance is better. But the premise is that concrete mortar must have sufficient strength and durability to ensure their own and the interface do not occur freeze-thaw damage ahead.②Admixture such as fly ash and silica fume in the framework concrete, can effectively improve the frost durability of concrete, and the effect of silica fume admixture is better than fly ash.Concrete framework structure model theory is a new concrete theory after the mortar model theory. Since this mathematic model is on the basis of a physical model which could open out the essence of concrete microscopical structure, it will embody more adequately how much every ingredient in concrete has contributed to the integrated performance of concrete in real sense. The research work in this paper only provides a new idea for the concrete research, and a more in-depth and comprehensive research is expected to improve the system of concrete framework structure model theory.更多还原