The Effect Of Pretreatment Of Seawater And Admixture On The Performance Of Concrete

Concrete is one of the most commonly used building materials in our daily life, but large amounts of fresh water will be consumed in its mix, maintenance and cleaning process which will undoubtedly brought great pressures to water resources. In recent years, the trend of seawater utilization in building materials has become a higher demand, but the large amounts of chloride and sulfate contains in the seawater will affect the performance of concrete and limits the application of seawater. Therefore, in the future research work, mixing with seawater to meet the durability requirements of concrete will have far-reaching significance.By the ultra-high lime with aluminum process test, it can be concluded that the removal rate of chloride ions is substantially peak after the reaction of 2.5h. When the feed ratio of calcium hydroxide and sodium aluminate as n（Ca）: n（Al）: n（Cl） = 3:2:1, the chloride ion removal rate reached 77.6%. The reaction is mainly generated four kinds of sediment Ca₄Al₂O₆Cl₂·10H₂O, Ca₂Al（OH）₆Cl·2H₂O, Ca₂Al（OH）₇·3H₂O and Ca₃Al₂（OH）₁₂, two of the chlorine-containing precipitate to remove chloride ion main reaction product.Mineral admixtures can improve the resistance of concrete to chloride ion penetration and resistance to sulfate attack. When three kinds of mineral admixtures are expected to single mixing, the electric flux of through concrete will be decreasing as the dosage of admixture increased. For corrosion resistance coefficient of concrete, the dosage of fly ash and coal gangue was between 25% 35% when reach the maximum, and the best dosage of metakaolin on concrete corrosion resistance coefficient vary from the mixing water. When mixed, the effect enhanced of mineral admixtures for the permeability resistance and sulfate attack resistance of concrete from big to small is fly ash and metakaolin > coal gangue and metakaolin > fly ash and coal gangue.The results show that when fly ash, coal gangue and metakaolin were content to 20% replacement of cement, that could reduce the amount of chlorine ions dissolved dynamic mortar, and their ability to influence the curing chloride magnitude relationship is: Coal> Partial kaolin> ash.When three kinds of mineral admixtures are single and complex mixed into the concrete, can significantly reduce the concentration of water-soluble and acidsoluble chloride ions, improve the ability of concrete combined with chlorine ions, increase the value of the polarization resistance of rebar in concrete and reduce the level of corrosion of reinforcing steel, thereby improving the durability of concrete.