Concrete Mix Design And Temperature Control Of Bridge Mass Concrete

With the rapid development of road transportation infrastructure in China, Long-span bridges continuously emerge in highway bridges while mass concrete has been increasingly applied in bridge engineering. The hydration heat of cementitious materials in bridge mass concrete as well as thermal cracks caused by hydration heat has also obtained more and more attentions. If the structural form and concrete mix are well-designed together with effective temperature control, it is possible to avoid harmful thermal cracks in mass concrete structures. In this paper, by taking a real mass concrete engineering of Lishui River Bridge as an example, the problems of concrete mix design and temperature control have been investigated:(1) Through the orthogonal experiment of concrete mix,the influences of cement type, water-binder ratio, fly ash and concrete admixture on compressive strength, tensile strength, workability and setting time of mass concrete is analyzed.(2) On the basis of orthogonal experiment, the compressive strength, tensile strength, workability and setting time of mass concrete are checked by analytic hierarchy process (AHP). The concrete mixes are compared according to the quality that provides a reference for deciders to select optimized concrete mix. (3) The concept of concrete conditional temperature rise test is proposed and the test is done in this work. The results for the conditional temperature of three optimum concrete mix are compared. The results show that the concrete conditional temperature rise test is economical and simple, and can satisfy engineering needs.(4) The finite element model of the spread foundation of the tower is established by using finite element analysis software MIDAS/Civil. The thermal field and thermal stresses during construction period is simulated. The construction procedure of mass concrete casting layer by layer is proved reasonable. It provides a reference and basis for the construction and temperature control of mass concrete engineering.(5) Based on the existing experience in engineering, combined with the actual situation in Lishui Bridge, the reasonable temperature control indexes are developed that ensures the temperature control scientific and reasonable. The purpose to effectively prevent thermal cracks is reached. The effect of temperature control is evaluated and the experience for the similar temperature control of bridge mass concrete is accumulated.