Expansion of Early Age Cracking of Concrete

The change and distribution rule of early temperature and strain of concrete were examined.Based on these study,some other researches are made concerning when and where will rise the concrete cracks in strip constructions.It has been shown that the early tension strain of concrete has undergone three stages: i.e.sharp rise,decline and stability.The first stage ends when the concrete is poured for 36~48 h,and the second is for 192~240 h.The maximum tension strain of concrete starts when the concrete is poured 36~72 h;The early temperature of concrete undergone three phases: i.e.rise,decline and stability.The first phase ends when the concrete is poured for 9~12 h,and the second is for 264~288 h;In the process of temperature rise,some statistical relationship can be found among temperature of concrete,between temperature of concrete rise rate and the height.In the process of temperature descending,the statistical relationship between temperature and time is obvious too.The early age crack occur most likely in the middle lower part of the strip construction when the concrete was poured for 24~48 h.A relatively accurate prediction of possible cracking zone in the early age of concrete was tensile strain of early age,the largest contraction strain and strain difference of the concrete.