Study On Mechanical Property Of Manufactured Sand Concrete And It's Prestressed Beams

Concrete is one of the main building materials in engineering construction. With the rapid development of infrastructure construction and more attention being paid to environmental protection, and the available and high quality natural sand resources dwindling, nowadays natural sand can not meet the need of increasing engineering construction. This becomes an increasingly prominent conflict in the construction industry. Using the manufactured sand rather than natural sand in the concrete is very important to resources conservation and environment protection. Thus the development, research and application of manufactured sand has been paid much more attention to. Manufactured sand concrete has been used to a certain amount in housing construction, hydropower, water transportation and other fields, but the study on its property is not deep enough and its application is not extensive, especially in pre-stressed concrete bridge projects of highway and railway construction which needs huge amount of sand. Therefore it's very necessary to further study the performance of the manufactured sand and manufactured sand concrete. In this paper, a systematic experimental research on the physical and mechanical properties of the manufactured sand and manufactured sand concrete by combing the need of applications of manufactured sand in the pre-stressed concrete bridge. The experimental researches of the mechanical properties of manufactured sand pre-stressed concrete beams under static and fatigue loads are done, and the mechanical characteristics of the manufactured sand concrete and the manufactured sand pre-stressed concrete beams are analyzed. An appropriate design methods is also proposed. All these provided the basis for the extensive application of manufactured sand in engineering construction, especially in the pre-stressed concrete bridge engineering. The main work and achievements in this paper are shown in the following.1. The physical and mechanical properties of the manufactured sand and natural sand are compared in the experiment. The result shows that the formal made manufactured sand could achieve good gradation and its physical property could meet the requirements of ordinary concrete The mixture ratio calculation method of ordinary concrete was also suitable for the manufactured sand concrete. In order to improve the workability and work performance, it is recommended to add appropriate amount of fly ash and extend the mixing time about 10 seconds.2. By systematic comparison test on the basic mechanical properties of the manufactured sand concrete and ordinary concrete, it is found that the cubic compressive strength, axis compressive strength, split strength and elastic modulus increased with the replacement rate increasing, and shrinkage deformation decreased as the replacement rate increased. The manufactured sand concrete was fully applicable to pre-stressed concrete. The relationships between concrete cube compressive strength and the axial compressive strength, splitting tensile strength, modulus of elasticity were established, which provides a reference for the application of manufactured sand concrete in pre-stressed concrete bridge engineering.3. Eight simply supported beams of manufactured sand pre-stressed concrete (5 of them are fold line pre-tensioned beams,2 of them are parabolic line post-tensioned beams and 1 was linearity post-tensioned beam) were designed. The load and strain of pre-stressed reinforcement tendon and concrete with manufactured sand were monitored during the whole production process, and the prestress loss of test beams was analyzed. All these indicated that the prestress losses of pre-stressed manufactured sand concrete beams can be calculated by the current formulas or principles in the Code. And the total prestress of pre-stressed manufactured sand concrete beams was less than that of pre-stressed concrete beams with natural sand.4. Through the experimental study of the mechanical properties of 5 pre-stressed concrete beams (3 of them are fold line pre-tensioned beams,2 of them are post-tensioned beams) under static load, the strain of concrete, non-pre-stressed bars and steel strand, the condition about cracks developing and changes of deflection between manufactured sand concrete pre-stressed beam and normal concrete pre-stressed beam are comparatively analyzed in every phase. The results show that under the same conditions the crack width and the deflection of manufactured sand concrete pre-stressed beams are smaller than normal concrete pre-stressed beams. The bending capacity, crack width and deflection of the manufactured sand concrete pre-stressed beam can be calculated by using the current formulas in the code and the calculated results are reasonable and have large guarantee rate.5. Through the experimental study of the mechanical behavior of three pre-stressed concrete beams(2 fold line pre-tensioned beams and 1 post-tensioned beams) under the condition of fatigue load, the cracks and the laws of deflection change between manufactured sand concrete and common concrete pre-stressed beams in the process of fatigue force and static load are compared and analyzed. The result shows that the mechanical behavior of manufactured sand concrete pre-stressed beams is superior to the common concrete pre-stressed beams. For the mechanical property of manufactured sand concrete pre-stressed beams, the related formula in current specifications can also be applied to the calculation of their residual bearing capacity, cracks and the deflection. They have enough reliability and guarantee rate. The study offers basis for the applications of manufactured sand concrete pre-stressed beams to bridge engineering under fatigue load.6. Based on the experimental study and the normal section theory, the analysis method of the pre-stressed manufactured sand concrete beams is proposed and the according program is compiled. The results of numerical analysis are in line with experimental results closely. The numerical analysis could be applied to the analysis of mechanical property of pre-stressed concrete beams with manufactured sand as well as pre-stressed concrete beams with natural sand.