## 3 Results and Discussion
### Alkali-Aggregate Mitigation by Pozzolanic Additions in Cement Mortars  
The alkali-aggregate test method prescribed by the Spanish standard UNE 146508 [33], which is equivalent to the American standard ASTM C-1260 [38] was selected to assess the ASR mitigation potential of natural pozzolan, P, siliceous coal fly ash, V, silica fume, D, and blast-furnace slag, S, additions present in blended cements in the percentages shown in Table 1. This study was developed using mortars made with three aggregates (non-reactive siliceous sand, ASJ_2 (Figure 6); siliceous gravel with moderate reactivity, VB (Figure 7); and a reactive siliceous pebble, ASJ_12 (Figure 8). Mortar bar expansion measurements were taken from two until 90-days. Figure 5: Open porosity results of the mortars made with the three aggregates and four additions added in four percentages of 20%, 30%, 40% and 50%: (**a**) natural pozzolan, P; (**b**) siliceous coal fly ash, V; (**c**) silica fume, D; (**d**) blast-furnace slag, S.  
Figure 6: _Cont._  
Figure 6: Alkali-silica mitigation by pozzolanic additions in mortars made with the non-reactive siliceous sand, ASJ_2, and four additions mixed in four percentages of 20%, 30%, 40% and 50%: (**a**) natural pozzolan, P; (**b**) siliceous coal fly ash, V; (**c**) silica fume, D; (**d**) blast-furnace slag, S.  
Figure 7: Alkali-silica mitigation by pozzolanic additions in mortars made with the siliceous gravel with moderate reactivity, VB, and four additions mixed in four percentages of 20%, 30%, 40% and 50%: (**a**) natural pozzolan, P; (**b**) siliceous coal fly ash, V; (**c**) silica fume, D; (**d**) blast-furnace slag, S.  
The average expansions, of three mortar bars for each pozzolanic material, for 90 days of exposure to 1M NaOH at 80 \({}^{\circ}\)C are shown graphically in Figures 6-8. The mortar control specimen, with no partial replacement of cement, CEM I, by pozzolanic materials, showed that ASJ_2 was a non-reactive aggregate, VB was a moderate reactive aggregate and ASJ_12 was a highly reactive aggregate with an average expansion exposure of 0.22% after 14 days, which was more than the threshold level of 0.2% specified as reactive by UNE 146508 [33]. All the mortar samples with partial replacement of cement by the four pozzolanic materials showed improvement in the ASR performance in different levels with a general decrease in the average expansion measured in three samples. Considering each type of pozzolanic material employed in this study separately, the results evidenced that the higher partial replacement of cement with any of the four pozzolanic materials was effective in improving in ASR resistance. The average expansion of mortar bar results made with the moderate reactive aggregate and with different amount of natural pozzolan partially replacing cement were V \(<\) P \(<\) D \(<\) S (Figure 7). This trend was also observed with the high reactive aggregate (Figure 8). All the expansion results shown in Figure 6 fall in the area between the origin of the graph and the points 0.1% and 14-days. Therefore, this (ASJ-2) is a non-reactive aggregate. The accelerated expansion mortar bar test was extended for 90 days to study the effect of the four pozzolanic materials. In the case of the blended cement mortars, it was clear the positive effect of the addition, i.e., the higher the pozzolanic material content in the mortar is, the higher the ASR mitigation is found. However, 5% or 10% of coal fly ash in the mix has no effect on the expansion evolution. The addition of 20% and 30% V presented a positive effect, while 40% V exhibited the best performance, i.e., mortar bar expansion below 0.1% at 90 days. Similarly, a content of 3% of silica fume in the mortar bar has no effect on the expansion evolution.