【正文】
ion ? Segregation is the tendency for separation between large and fine particles of fresh concrete. ? Segregation results in ? Rock pocket /honeyb 蜂窩 ? Sand streaks 砂條痕 ? Crazing 龜裂 ? Surface scaling 表面剝落 Segregation ? Reasons of segregation ? Very wet mixtures, lack of fine particles, high slump concrete, Overvibration ? Controlling segregation ? Airentainment ? Finely divided materials ? Dropped vertically Bleeding ? BleedingA concrete mix that does not possess proper consistency is unable to hold the mix water, which slowly gets displaced and then rises to the top of the form. ? Reasons of Excessive bleeding ? Overvibration, overtroweling, lean mixes, lack of fine sand, premature finishing ? Controlling bleeding ? Airentainment ? Increase the fineness of cement ? Decrease watertocement ratio ? Rich mixes Bleeding