Abstract: Through the carbonation test of admixture concrete under natural exposure condition, the influence laws of fly ash content, slag content, coal gangue content on the carbonation depth of concrete were analyzed, and the interaction of double-mixed admixtures on the concrete carbonation depth was also discussed. On basis of experimental data, an expression of the influence coefficient of mineral admixture on carbonation speed was established. The results show that the carbonation depth of concrete decreases slightly when the content of single mixing fly ash is less than 15%, and concrete carbonation depth increases with the increase of fly ash content after its content is more than 15%. The carbonation depth of slag powder concrete increases with the increase of slag content. The anti-carbonation performance of concrete increases when the content of single mixing coal gangue is less than 20%, while mixed with more than 30% of coal gangue, the concrete carbonation depth increases significantly. Along with the increase of fly ash content, the carbonation depth of both concrete mixed with fly ash and slag powder and concrete mixed with fly ash and coal gangue increases, concrete carbonation depth changes smaller after in the fly ash concrete adding 25% slag or 20% coal gangue. In the coal gangue concrete adding 25%-40% slag powder, the concrete carbonation depth has no obvious change, while the carbonation depth increases obviously when it mixed with more than 40% of slag powder. In the slag powder concrete adding 20% coal gangue, the concrete carbonation depth will increase by about 40%.

Key words: concrete;admixture;carbonation depth;influence coefficient of mineral admixture on carbonation speed