The Relationship Between Mesostructure/Microstructure And The Strength Of Concrete

The strength of concrete is an old topic. As awareness of buildings' safety and the use reliability enhancing, more performances of concrete are requested. Although we will pay more attention to durability and impermeability of it, strength's importance is unshakable. Strength is the most fundamental impact in structure performances, and needs to be considered primarily in structure designing, quality testing, etc.. Correct understanding of the mechanism of strength development and impact factors are very important for concrete structures designing and quality assurance.The natures of material's macro-structure are subjected to the natures of it's compositions, the performances of materials (particularly mechanics performance) depend on the internal structure. Without the research of micro-level (or mecro-level), or without understanding the regulation of it, concrete technology can not be divorced from empirical constraints. In homogeneous materials, macro- performance is directly controlled by micro-structure. Heterogeneous materials such as concrete, which performance has closer ties with it's mecro-structure apparently than micro-structure. It remains confined to the analysis of the microstructure of the nature and value of various bond, it is worth further study.Considering more factors,establishing expressions with physical meanings,and begin with the most basic unit's nature will make the study of concrete properties more completely and correctly. So five sections of this reads include the following aspects:Chapter I analyzed the relationship between micro(mecro)-structure and macroscopic properties. Reviewed the strength theories and failure theories of concrete, illuminated that strength has something to do with the pores and bindingpower with Griffith-Гордон theory and crack expansion mechanism. Chapter II analyzed pore structure which effect the strength of concrete. Summarized the quantitative relationship between pore structure and strength with the correlative models. Make comparations between these models,and bring forward an improved one. Chapter III deduced a new formula to the failure probability of the matrix material of a loaded porous structure by combined Fractal dimension with the weakest link model. In this model author introduced Fractal dimension to describe the Complexity of pore size distribution. Chapter IV analyzed various bonds in the concrete,determined strength composings in micro-level. In a specific way computed the attractive power made by hydrogen bond between C-S-H layers. Proposed the assumption that Van der Waals forces play a decisive role in the strength of the concrete. Chapter V took Van der Waals force as the representative, analyzed the condition which makes C-S-H cracking. Combining the solid physics and micromechanics, with the structure characteristic and constitute of C-S-H for basis, computed the crisis force that makes cement damage at different w/c. Chapter VI for the whole conclusion of article and prospect, tallied up the textual result, and put forward the suggestion to the further research contents and direction.