Papers by Keyword: Mass Concrete

Abstract: This paper examines the structural, workability, physical and mechanical properties of (mass concrete) with the inclusion of microcapsule of Zinc oxide (ZnOMC) with a size (0.5) µm and in different percentages (0, 0.5, 1 and 1.5) % of cement weight. The proportions of the concrete mixture were (1:2:4.8) and the water-cement ratio (W/C) was 0.4. 0.6% of Superplasticizer (SP) by weight of cement with all concrete mixtures was added. An SEM analysis employed to obtain a better view of the concrete behavior with ZnOMC. Referring to the analysis and discussion, it was found that the types of microcapsule used to have an effective effect on the compressive and flexural strength and mechanism of sealing the crack, also the highest percentage of microcapsule which there has a positive contribution towards mass concrete properties have been recorded.

Abstract: Early-age cracks in shaft concrete has become a serious problem in 1000m-plus deep mine due to the high internal temperature and thermal stresses. For the purpose of improve the cracking resistance of concrete, we report a novel experimental design by Temperature Stress Test Machine (TSTM) to study the influence of three fibers including basalt fiber, polyvinyl alcohol fiber and steel fiber on early-age cracking resistance of shaft wall mass concrete. Results of the experimental research indicated that (1) Three fibers can restrain expansion and shrinkage deformation finitely, and the shrinkage resistance effect of different fibers was steel fiber>polyvinyl alcohol fiber>basalt fiber; (2) Three fibers can finitely reduce the tensile stress increasing speed which was basalt fiber>polyvinyl alcohol fiber>steel fiber during; (3) The main function of fibers is restrain crack expansion and brittle failure rather than reduce cracking potential, and the rank of function is steel fiber>basalt fiber>polyvinyl alcohol fiber.

Abstract: The surface convective heat transfer of mass concrete is an important element of concrete structure temperature effect analysis. Based on coupled Thermal Fluid governing differential equation and finite element method, the paper calculated and analyzed the dependence of the concrete surface convective heat transfer on the air flow velocity and the concrete thermal conductivity coefficient. Results show that the surface convective heat transfer coefficient of concrete is a quadratic polynomial function of the air flow velocity, but influenced much less by the air flow velocity when temperature gradient is dominating in heat transfer. The concrete surface convective heat transfer coefficient increases linearly with the thermal conductivity of concrete increases.

Abstract: Combined with engineering examples, describes the reasons for the large volume of concrete cracks proposed comprehensive measures to control cracks from all aspects of mass concrete harmful cracks eliminate achieved remarkable results, for the future of similar mass concrete construction provides some guidance .

Abstract: The paper analyzed the temperature control technique measures of mass concrete in the pile cap of main pier in Yangtze River Bridge. Consider the effect of the cooling pipe, ANSYS finite element analytical software was used to calculate the temperature field of the pile cap in the construction, the distribution rules of the temperature field was simulated by finite element analysis. It is shown that the cooling effect of the mass concrete is obvious by using cooling water pipe, the finite element calculation results can be used to lead to the design and construction. It also provides the reference to develop a reasonable temperature control solutions during the construction of the similar mass concrete.

Abstract: Combined with practical engineering，this paper analyzes the mechanism of mass concrete temperature and shrinkage cracks, from raw material selection, structure design, construction, monitoring and management five aspects,the author respectively gives the countermeasures on temperature and shrinkage crack of mass concrete, reference for engineers.

Abstract: Abstract. It was based on bridge anchor structure of three gorges reservoir area, from the perspective of enhancing the anti-permeability performance of mass concrete, taking into account the economic perspective, with the use of large dosage of fly ash and slag powder to replace cement to reduce the water-binder ratio and hydration heat, improve the anti-permeability performance of concrete, according to the characteristics of mass concrete. Through the test, the influence law of admixtures on impermeability of C30 mass concrete were obtained, and at the same time the better mix proportion of C30 anti-seepage mass concrete used in bridge anchor structure was recommended.

Abstract: Mass concrete is widely being used in the construction field, especially for the foundation of super high-rise building. In the initial stage of pouring completion of mass concrete, lots of heat generated from the cement hydration will lead to a high temperature inside of concrete. When the temperature difference between the inner and outer of concrete exceeds the limited value, thermal stress will be greater than the tensile strength of concrete, which may cause hazardous penetrating cracks of the structure. To ensure the safety and durability of concrete structure, necessary measures should be taken to control the temperature rise and construction quality of concrete. Taking a super high-rise building project as an example, this paper introduces several effective solutions to resolve above problems. The technical measures such as enhancing the concrete quality, controlling temperature rise, strengthening temperature monitoring would be detailed illustrated. Meanwhile, valuable suggestions achieved from this practical project are proposed in order to guide the structural design and on-site construction of similar projects.

Abstract: This study is conducted to evaluate analytically the effect of casting temperature on the heat of hydration in mass concrete foundation with ternary cements and Type IV low heat cement. The mat foundation has the dimension of 15m length, 20m width and 3m depth. Casting temperatures considered for mat foundation consist of 10, 20 and 30C ̊. A commercial software MIDAS/Gen was used to analyze the hydration heat of mass concrete foundation. The maximum adiabatic temperature rise (K), and the coefficient of temperature rise˰˸α˹˰for thermal analysis were drawn from adiabatic temperature rise test. Analytical results show that blended cement PSLB_352 is the most effective to control the heat of hydration in mass concrete foundation and external temperature increases the maximum heat of hydration and crack probability of mat foundation with mass concrete.

Abstract: This study provides analytical results for heat of hydration in the mat foundation with mass concretes to investigate the effect of lift thickness in the mat foundation on the hydration heat and crack characteristics of mat foundation with mass concrete. Mass concretes were mixed with ternary cement with 1% strontium-based latent heat binder at volume fraction and Type IV low heat cement. The mat foundation has the dimension of 15m length, 20m width and 3m depth. Lift thickness of mass concrete for mat foundation was varied from 1.0m to 3.0m. A commercial software MIDAS/Gen was used to analyze the hydration heat of mass concrete foundation. The maximum adiabatic temperature rise (K), and the coefficient of temperature rise (α) for thermal analysis were drawn from adiabatic temperature rise test. Based on the results of the finite element analysis for mat foundation with different lift thickness, the highest internal temperature and thermal stress increased with increasing with lift thickness of foundation. However, for foundation constructed with premixed strontium based latent heat binder (PSLB) concrete, this phenomenon was less remarkable compared to mass concrete foundation made with low heat cement.