Yue Li;Xiongfei Liu;
<正>Since concrete cracking has always been a primary factor that reduces the durability and applicability of the concrete,it draws more and more extensive attention by both international academia and engineers in recent years.Unfortunately,the research on the early micro-cracks is not sufficient,although it is a serious issue.It is well known that the presence of microscopic crack is an important reason causing the development of macroscopic crack.Under the influence of external conditions,micro-cracks can develop gradually into the macro-cracks.Therefore,only when the internal stress field in the cement paste is made clearly can the micro-cracks be effectively controlled,and then can the macro-crack be reduced,which will improve the durability of concrete. In order to analyze the internal stress field in the cement paste,a simplified model of the cement paste under the restricted condition was designed,and the parameters in the model were gotten by some experiments.As a result,a theory formula and calculating method about the internal stress in the cement paste under the restriction by a large elastic core body(such as aggregate and un-hydrated clinker) are established,which is based on the theory of elastic mechanism.Based on this formula,the influencing factors on the internal stress in the cement paste were further analyzed,and the law of strain variation under the large elastic core confinement was discussed.The research results are of practical significance for controlling the concrete crack development and improving the durability of concrete. Originality The process of concrete using with cracks will greatly reduce its working performance. If the cracks can be effectively controlled,the durability of the concrete will be highly heightened.To face the problem,a simplified model of the cement paste under the restricted condition was designed,which can control the development of the micro-cracks in microcosm.After the parameters in the equation were well adjusted,the major influencing factors that generates micro-cracks will be well analyzed.Further more,when the generation of the macro-cracks were effectively reduced,with the control of external environment,the macro-cracks were largely reduced and controlled. As a result,the concrete were made full use of in the engineering.Hence,the durability and the practical applicability were enhanced.
large elastic body;;micro-crack;;internal stress;;elastic mechanism;;formula
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