volume shrinkage
2.For the active filler?containing system, the theoretical density not only relates with the ceramic yield of the polymer and the density ratio between the pyrolysis product and polymer, but also relates with the reaction yield and density ratio of the active filler after reaction, and the volume shrinkage of the composite.
5.Early age cracking of concrete has re-emerged as an important issue all over the world in recent years.The stress,due to restrained volume change related to thermal deformation and shrinkage in the early age concrete,is the main driving force for the deleterious cracking in the construction stage.During the development of the stress,creep,a very important property of concrete,is always developing.Creep contributes to 40?-50? reduction of the elastically induced stress in the restrained specimen.Ring test,a qualitative test,can provide information to assess the potential for cracking of different concrete.An overview of ring test developed in recent years and mechanism of uniaxial tensile creep test is described in this paper at first.Then,an innovative test equipment based on ring test is outlined.
6.The strength,strain and shrinkage properties of the high volume fly ash concrete with 50wt% fly ash and without expanding and water-repellent admixture,which were cured at standard,atmosphere and varying temperature condition respectively,can meet the requirement of the high volume concrete engineering(C40P8) for the main building of CCTV New Site Construction & Development Program.
7.In the design, the construction measures such as application of shrinkage-compensating concrete, arrangement of spacing layer between the foundation rock and the bottom slab, adding outside waterproof layer, flexible connection between outlet pipe with side-wall, integerated concrete placement of pump seat with bottom slab and design of reinforcement with application of advanced calculation theory are used according to the characteristics of lager span, larger volume and complex loading conditions of the understructure.
8.All concrete structures are exposed to volume changes caused by hydration reactions in the early age.If the volume changes are restrained,stresses is generated which will cause cracking when it overcomes the tensile strength.As the mechanical properties of early age concrete vary with time,especially the creep degree depends on the time elapsed and the time at loading,to calculate the stress of concrete structure is a complex nonlinear problem .The finite element method (FEM) can take account of the evolution of the stiffness properties,the development of thermal strain,creep,shrinkage and so on.In this paper,a general approach for numerically simulating this type of behaviour is presented firstly.Then,how to solve this problem is introduced by the general finite element software ANSYS using the Initial Stress Method.Finally,a detailed description of an example calculation that demonstrates the potential of the numerical simulation strategy follows.
