The effect of mineral admixtures such as nano silica, micro silica, fly ash and ground granulated blast furnace slag on the expansion of mortar bars caused by internal and external sulfate attack was investigated. According to data recorded through 12 months, all of the mineral additives, particularly slag, have significantly reduced the expansions caused by sulfate attack. It was shown that, the effectiveness of nano silica was also very significant. When used with sulfate contaminated sands, high sulfate resistant mixtures were produced with 4-6% nano silica replacement ratios. In the case of external sulfate attack, however, only 2% nano silica is most likely enough for keeping the expansions below 0.03% after 12 months. (C) 2011 Elsevier Ltd. All rights reserved.