ABSTRACT
The pylon of main navigational channel bridge of Hutong Changjiang River Bridge belongs to C60 high-strength strongly restrained mass concrete structure with outstanding early age shrinkage cracking risk. By using isothermal calorimeter, the influences of sucrose and hydration regulation material on cement hydration were experimentally studied. At the same time, an experimental investigation was made to research the effect of the additions of CaO and MgO expansion components on the early deformation of concrete under the actual temperature history by employing the environment simulation test chamber. Then a scale model experiment was carried out to evaluate the coordinate regulation effect of the above anti-cracking function materials. The results indicated that different from retarders e.g. sucrose, the cement hydration rate at acceleration period was reduced by 50% by the use of 0.2% hydration regulation material. Meanwhile the expansion of concrete at temperature rise stage doubled and shrinkage at temperature fall stage decreased by about 30% as a result of the composite addition of 4% CaO and 4% MgO with 160±10 s reactivity value. The temperature peak value of scale model concrete containing the above anti-cracking function materials decreased by 6.4 °C compared to the reference concrete. The expansion at temperature rise stage doubled and shrinkage at temperature fall stage decreased by 100 με. Finally, Low temperature-rise and high crack-resistance concrete prepared based on the coordinate regulation technology of cement hydration rate and expansion process has been applied in the pylon on Pier No. 29 of Hutong Changjiang River Bridge. The central temperature rise, temperature differences between center and surface and shrinkage deformation were all decreased obviously, therefore the crack resistance performance of pylon mass concrete was improved effectively.
