Research And Application Of Low Temperature Rising And Anti-cracking Mass Concrete

The mass concrete structures are widely used in the construction of the bridge project, which are often leading to structural cracks because of temperature stress. Now mainly taken the cooling pipe measures to prevent temperature cracks, during the construction process. However, in this way not only increases the difficulty of construction and cost, while after grouting the cooling pipe place is still not dense, which will leading to the harmful ions easily penetrated into concrete, affecting the service life of the structure. So explore a design method of mass concrete, achieving cancel cooling water pipe, is imperative.This article rely on the Guangdong Provincial Department of Communications project "Fuzzy control technology of the mass concrete construction". Integrated design of mass concrete anti-cracking measures to address large volume concrete crack problem that with the "low temperature rising and anti-cracking mass concrete mix design and gradient structure design" method, this article has the following research:The influences of molding temperature (15℃、25℃、35℃) on the adiabatic temperature rise of mass concrete were researched in this article. Changing rules and mechanisms of the hydration exothermic quantity and hydration exothermic rate under different influence factors, type and dosage of mineral admixtures and casting temperature, were also discussed. The exothermic replace coefficient (Nt) was proposed to characterize hydration exothermic quantity of mineral admixtures per unit mass relative to that of cement. Considering the molding temperature, calculation formula of cementitious materials in mass concrete discipline was revised, which can be a good reference for adiabatic temperature rise calculation in mass concrete structures lacking experimental condition.Proposed the low temperature rising and anti-cracking mass concrete mix design method, which basis on the dense principle, through adjustment the scale of each cementitious materials and mixed the mass concrete special concrete water reducer these two kind of method that to achieve the balance of the concrete mechanical properties improvement and the adiabatic temperature rise reduce. Prepared the mass concrete that meet the need of different structural parts. For C30-C50low temperature rising and anti-cracking mass concrete, which’s mechanical properties close to normal mass concrete, but3day hydration heat of concrete dropped,18.8%and7.7%, respectively. Proposed the mix design method of the high toughness&anti-cracking concrete and the abrasion-resistant mass concrete. The durability test shows, all those type of concrete are meeting the durability requirements of bridge high performance concrete.Proposed the gradient design method of mass concrete structure. Through the "low temperature rising and anti-cracking mass concrete mix design and gradient structure design", which achieve reduce of structure temperature and enhance the anti-cracking characteristics (abrasion-resistant characteristics) of the structure edge at the same time. Combination of those method above, which effectively solves mass concrete crack problem that widely appeared at the bridge engineering.Research results were applied successfully on the mass concrete brige structure parts of the Jiashao bridge, the second bridge of Daxie and the crossing Chu river bridge of Zhongbei Road. And all the application is successful. The engineering application practice shows that: low temperature rising and anti-cracking mass concrete made by this method controlled the inside and outside temperature difference and temperature stress effectively. And the temperature stress was lower than the splitting tensile strength of concret under the same age. There was no cracking phenomenons in the above structure parts.