RESEARCH AND APPLICATION OF ANTI-CRACKING TECHNIQUES FOR DUMBBELL-SHAPED CAP BLOCK CONCRETE

The issue of crack resistance of dumbbell-shaped block concrete for caps of the newly built Xinhe Bridge in Wuhan was studied, the comprehensive measures were adopted such as techniques of temperature control casting concrete, temperature rise control for hydration heat and shrinkage compensation. The results showed that the key to reducing the temperature of casting concrete was the temperature control of mixing water and coarse aggregate; the temperature rise of concrete for hydration heat could be significantly reduced through circulating hydration heat regulating materials in cooling water pipes; the shrinkage of block concrete during the drop phase of temperature could be significantly compensated by the magnesian expansion agent, however, more stringent insulation measures should be taken to avoid the excessive surface strain difference between the interior and the surface resulting in increased risk of crack. Practice showed that good and precise control measures of temperature and effective compensation measures for concrete shrinkage were the key to crack resistance of block concrete.