Experimental Reserach On Attack And Freeze-thaw Properties For Silica Fume Fly Ash Concrete Under Seawater Environment

Marine concrete is gradually developing with continuous exploitation and research for oceanographic engineering. Because of the dreadful situation, the concrete’ service life in our country is usually less than 30 years. Therefore, the erosion and freeze-thaw properties of concrete have become scholar’s focus. And how to keep nice resistance towards erosion and freeze-thaw in marine concrete has become the key factor for oceanographic engineering safety. So studying the erosion and freeze-thaw properties for silica fume fly ash concrete is of vital importance for lengthening marine concrete’s service life.In this paper it is assumed that the concrete suffers erosion from sulfate in summer and freeze-thaw in winter respectively under seawater.In response to the assumption, the deterioration model for single and combined action of sulfate erosion and seawater freeze-thaw on silica fume concrete, fly ash concrete, silica fume-fly ash concrete and ordinary concrete are analyzed. Relative dynamic modulus of elasticity,mass loss, and relative compressive strength are selected as damage evaluation indexes in sulfate erosion experiment, seawater freeze-thaw experiment, and combined action experiment of sulfate erosion and seawater freeze-thaw to analyze the deterioration law of the concrete.As applied basic research, main conclusions in this paper can provide experimental data and theory reference for research and design for concrete durability in oceanographic engineering. The main contents of this paper are summarized as follows:Firstly, experimental study on strength development law for silica fume fly ash concrete (SFAC) has been carried out. The results show that the compressive strength of SFAC reach peak when the percent of silica fume is 5% and the fly ash is 30%.Secondly, test studies are conducted for sulfate erosion properties of SFAC, SFC, FAC, and PC, and the relative dynamic elastic modulus,mass loss and strength loss are used as evaluation indexes to analyze change rules for the four kinds of concretes. The results show that the resistance against sulfate erosion of SFAC is best, and, its mass and strength increase first and decrease later. The relative dynamic elastic modulus keeps decreasing constantly.And then, seawater freeze-thaw test studies are conducted for the four concretes, and the surface damage, relative dynamic elastic modulus,mass loss and relative compressive strength are used as evaluation indexes to analyze deterioration law for the four kinds of concretes. The results show that the SFAC also has the best resistance against the seawater freeze-thaw. The surface damage becomes more and more serve with the increasing circles of freeze-thaw, meanwhile, the mass, relative dynamic elastic modulus and relative compressive strength keep decreasing.Finally, comparative analysis for SFAC between sulfate erosion and seawater freeze-thaw of same action time was carried out, which show that deterioration degree of SFAC in seawater freeze-thaw is more serve than it in sulfate erosion. Then, sulfate erosion and seawater freeze-thaw alternate cycle test on SFAC was carried out, and curve relationship between the alternate cycle times and surface damage, mass loss, relative dynamic elastic modulus, relative compressive strength is analyzed.