The Experimental Study And Comparative Analysis On Sulfate Resistance And Antifreeze Of Cement Concrete

With the rapid development of our country, the annual concrete amount can be up to several billions cubic meters due to large-scale construction. Many big programs being planned or under construction,such as Three Gorges Project, giant overriver or sea-crossing bridges, expressway and large airports , are invested much by state,and requirement of longevity is high.In those projects,high quality and durability are in great demand in order to extend the service life of them. Within the vast area in China, northeast ?ï¿ northwest and North China ,covering more than half of the territory , are all in cold area. With the western development , the urgent construction of many projects like railways, high grade roads, bridges, hydropower , civil aviation, gas and oil facilities situate in cold areas with large area of saline soil and salt lake which is adverse to the use of concrete in those projects.So to research the law of cement concrete ??s sulfate resistance and frost resistance is extremely important.Based on above reasons, we investigate the sulfate resistance and frost resistance of cement concrete of various mixing proportion and with different kinds of admixtures,reveal the law, analyse comparatively cement concrete ??s sulfate resistance and frost resistance from the aspects of basic theories and the test results,and present the instructive conclusions for construction. The paper is divided into several sections:In the first part, this paper introduces the content and significance of cement concrete ??s sulfate resistance and frost resistance research and propose the following research route: to comparatively analyse cement concrete ??s sulfate resistance and frost resistance on the basis of experimental study of them.The second part is preparation of cement concrete.This paper describes the basic physical index test of cement and coarse and fine aggregates and the effect of different admixtures in cement concrete, formulates different mixture ratio and introduces preparation methods of specimens , providing a foundation for further study of cement concrete ??s properties.In the third part, this paper introduces our research on the law of sulfate resistance of cement concrete of various mixing proportion and with different kinds of admixtures.It is proved that the water-cement ratio is a dominant factor in sulfate resistance ability of concrete. Lower water-cement ratio can significantly increase the density of concrete, and the concrete sulfate resistance capacity improves correspondingly. The density of concrete increases, that is reduction of the porosity of concrete, the smaller the porosity,the more difficultly water infiltrate, therefore, the speed and quantity of tricalcic sulfoaluminate generating will certainty become small,combined with increased density,so the intensity will generally raise, thus the sulfate resistance capacity will enhance. It also reveals the specific role of different admixtures in cement concrete sulfate resistance test .The fourth part is research of the law of cement concrete under freeze-thaw cycles. We investigate the mechanism of freeze-thaw damage, select groups according to the cement concrete sulfate resistance test results ,conduct antifreeze-thaw tests, analyse the quality and relatively dynamic elastic modulus curve of cement concrete specimen under the freeze-thaw action, and reveal the laws of frost resistance.In the fifth part, this paper analyse comparatively the sulfate resistance and frost resistance of cement concrete from aspects of basic theories and test results.In the end we study the synthetic effect of sulfate and freeze-thaw action on cement concrete.