Performances of industrial residue-cement solidified soils in resisting sulfate erosion

To promote application of the industrial residue in coastal soil solidification, the performances of the industrial residue-cement solidified soils (IRCS) in resisting sulfate erosion are investigated. Based on the combination of the cement and the industrial residues (ground granulated blast-furnace slag, fly ash, silica fume and calcium carbide slag), the mechanical behavior, microstructure and intrinsic chemical reaction of the IRCS after standard curing, water soaking and sulfate solution soaking are identified by the appearance observation, unconfined compressive strength, X-ray diffraction and scanning electron microscope tests. The obtained results show that: (1) The erosion of magnesium sulfate to the IRCS is higher than that of sodium sulfate. (2) Compared with the cement-solidified soils, the addition of the industrial residue can significantly alleviate the sulfate erosion. (3) After magnesium sulfate solution soaking, the strength of the IRCS is improved within 7 days and then descends continuously with increasing curing age. (4) The strength retention coefficient of IRCS follows the sequential order as ground granulated blast-furnace slag > silica fume > fly ash > calcium carbide slag. The IRCS in sodium sulfate environment is mainly affected by erosion of \textSO_4^2 - , while the combined effect of sulfate erosion and weakening cementation occurs in magnesium sulfate environment. It will result in the enlarged intergranular pores, and the reaction products are correlated with the CaO content contained in the industrial residues. Finally, the conceptual model for the microreaction mechanism of solidified soils in sulfate environment is established, which provides a theoretical basis for the researches on sulfate resistance of solidified soil.