## 3 Results and Discussion
### Chloride Transport Properties  
Figure 6 shows the evolution of the total chloride profiles with drying-wetting cycles for 120-day saturated mortar specimens blended with 65% slag. Similar shapes are observed for all drying-wetting cycles. A common peak of chloride content is found in the outermost part of 3-4 mm. The chloride peak is closely related to the accumulation phenomenon caused by intermittent drying-wetting exposure. The drying procedure led to the evaporation of free capillary water, and the evaporation front moved inwards as time elapsed. Some chloride ions moved outwards along with the water evaporation, and others precipitated in the capillary pores due to oversaturation. In the subsequent wetting procedure, additional chlorides, along with an aqueous solution, were absorbed into the first layers of the specimen. The absorption front can normally reach the depth of the previous evaporation front, as the wetting process is significantly faster than the drying process. The amount of fluid evaporated after 8 days can be re-saturated by absorption within 2 h, as reported by [PERSON] et al. [33]. The chloride content corresponding to the peak increased clearly with the increase in the cycles. Saturation of the chloride content in the skin layer was not observed, even after 70 drying-wetting cycles, implying that the maximum chloride binding capacity was not reached. In the inner part of the specimen, the chloride content decreased with the depth and seems to have followed a diffusion-controlled process of ingression. This indicates that the convection caused by cyclic drying-wetting plays an important role in chloride penetration only in the first millimeters of slag-blended mortars. Figure 7 displays the changes in the total chloride profiles in saturated mortar specimens of various slag contents after 10 drying-wetting cycles. The variation rule for the chloride content versus depth is basically the same, except that the chloride content was noticeably lower in the slag-blended binders than in the OPC binder. This observation is true for all different replacement levels of slag (25-85%). The 65% slag binder presented the lowest chloride content in the entire penetration depth. This can be intimately related to the  
Figure 5: Pore size distributions of 120-day paste specimens with increasing slag content. fineset pore sizes in the microstructure of the 65% slag binder, as already addressed earlier. With an increase in the depth, the chloride content increased first and then decreased. This again proves the limited influential depth of drying-wetting cycles, known as the convection zone, on chloride penetration, irrespective of the binder type. The convection zone seems to be smaller when incorporating the slag. The main reason can be related to the much finer pore structure in the slag-blended binders, for which the evaporation front during the drying procedure is expected to be smaller than that in the OPC binder. The chloride peak formed within the convection zone was observed to be apparently higher for the OPC binder. The larger porosity and associated coarser pore sizes are considered to be in charge of the peak amplitude in the first 10 cycles of drying-wetting exposure. The large pores provided more space for the external chloride solution to penetrate into the surface part of the specimen. Figure 6: Effect of drying–wetting cycles on the total chloride profiles in 120-day saturated mortar specimens blended with 65% slag. Figure 7: Effect of slag content on the total chloride profiles of saturated mortar specimens after 10 drying–wetting cycles. Figure 8 depicts the differences in the total chloride profiles of mortar specimens in the saturated and unsaturated states. For saturated specimens (S = 100%), there was a clear peak in the chloride content in the skin layer, and the peak became increasingly pronounced with the increasing drying-wetting cycles.