Papers by Author: Zhan Qi Guo

Abstract: The influence of concrete meso-structure and coarse aggregate size on early age crack is studied. In this study, concrete is regarded as a three-phase material based on shrinkage property. The mortar matrix and interfacial transition zones undergo shrinkage and no spherical coarse aggregate particles are considered to restain the shrinkage by particle interaction. The results show that concrete meso-structure plays an important role in the safety of concrete, different aggregate distribution in concrete leads to different initial cracks and propagation due to shrinkage. With the increase of maximum aggregate size, the value of shrinkage deformation becomes unstable and varies in a wide range; relevant shrinkage cracking becomes easier too.

Abstract: High-performance concrete will undergo severe damage under fire conditions. It is well known that vapor pressure induced by high temperatures plays an important role in the damaging process. This paper presents a method of vapor pressure modeling, called equivalent expansion method, which can be implemented in FEM analysis. The modeling procedure consists of two parts, i.e. vapor pressure determination and vapor pressure modeling incorporated in FEM analysis. In order to make analysis more accurate, steam table is employed instead of ideal gas equation.

Abstract: This paper presents the whole procedures that should be followed when carrying out the simulation analysis on the damage by fire to high-performance concrete (HPC). The whole procedures consist of temperature field determination, mechanical analysis, identification of damage to HPC related to thermal and mechanical behavior, structural behavior simulation and cooling stage simulation analysis. That the first two parts are essential to the whole analysis has been pointed out. The present simulation analysis situation is analyzed as well.

Abstract: A literature review was carried out to identify advances in research on workability of fresh concrete via both experimental tests and modeling, especially high performance concrete and self-compacting concrete. As to the relationship between fluidity of concrete and that of paste, future research can be conducted in two aspects, i.e. one is the influence of the quantity of paste in concrete, and another is the influence of fluidity of paste affected by a couple of factors. Most literature proved that the flow of concrete depends both on positive effect and negative effect, the former promote fluidity, such as dispersing, filling and lubricating, and the latter restricts fluidity, such as formation of particle coagulation, an increase of wettable surface of solid particles and mechanical interlock.

Abstract: A literature review was carried out to identify advances in research on workability of fresh concrete via both experimental tests and modeling, especially high performance concrete and self-compacting concrete. It is concluded that, in order to achieve better understanding of fresh concrete, especially self-compacting concrete (SCC) and high-performance concrete (HPC), a clear methodology of research should be established as the first step. It is suggested that there is no unique workability test method suitable for all the range of fluidity of fresh concrete, and a specific method should be identified for a proper range of fluidity. As to the relationship between fluidity of concrete and that of paste, future research can be conducted in two aspects, i.e. one is the influence of the quantity of paste in concrete, and another is the influence of fluidity of paste affected by a couple of factors.