## 3 Results and Discussion
### Properties in Hardened State
#### 3.3.3. Durability in Gelifraction Processes  
Freeze/thaw processes are one of the main causes of degradation of mortar and concrete [57] in cold climate regions [58]. The durability of the systems in the gelling processes has been measured for twelve hours in order to ensure that, when the ice formed in the cooling cycle melts, it melts completely and goes to liquid state [33].  
The speed of the ultrasonic wave velocity was measured in a TICO PROCEQ ultrasound meter with frequencies of 54 Hz and the relative dynamic modulus of elasticity was determined [34]. Compressive strength was determined according to UNE-EN 196-1 [26]. Porosity was measured by mercury intrusion with BET. The resistance to gelling was considered when the following occurred: (a) relative modulus of elasticity was equal to or less than 60 \({}^{\circ}\)C, and (b) breakage of the specimen with external cracking.  
Each mortar type manufactured: (1) two 80 \(\times\) 80 \(\times\) 400 mm prisms to measure the relative dynamic modulus of elasticity by means of ultrasonic wave propagation and weight variation and, (2) twelve 40 \(\times\) 40 \(\times\) 160 mm prisms to evaluate compressive strength before each freeze/thaw cycle and after 28, 62, and 114 cycles.  
The results obtained are presented in Figures 9 and 10 for mortars with 10% and 20% waste substitution from PR-1 granite sawdust waste. The maximum number of freeze/thaw cycles in which the structure remained after testing two specimens has been considered as standard, according to the data mentioned in Table 3.  
Figure 10. Variation of the relative dynamic modulus due to cracking failure.  
Figure 9. Variation of the relative dynamic module due to failure when reaching 60% failure.  
Mortars with substitutions have very similar behavior up to 45 cycles; a relevant fact, since the mortar without addition shows deterioration due to gradual failure, reaching the threshold value in those 45 cycles. In Figure 9, corresponding to 60% failure, it can be seen that the mortar with 20% addition is more resistant to gelling than 10% replacement.  
Something similar happens in the figure for cracking failure. The parity of mortars with replacement, both 10% and 20%, is different from that of mortar without addition and reaches longer times in terms of number of cycles. The porosity values obtained are provided in Table 4.  
Table 4 shows that the total porosity values are between 10% and 14%, with values similar to those obtained by [PERSON] et al. [59] for pozzolanic cements made from calcined paper sludge, which also coincide with those cited by [PERSON] and [PERSON] [60] in metakaolin-based pozzolans.  
The greatest strengths of mortars made with additions are related to the size of the pores. When 65 cycles are reached, the mortars show a distribution in which a secondary peak appears between 1 \(\upmu\) and 300 \(\upmu\)-that is, towards a smaller pore size. Mortar without addition has a larger pore size.  
Compressive strength values in mortars with addition once again influence the best results when it comes to binary cements--that is, with addition. [PERSON] [61] already carried out this evaluation with additions of silica fume and [PERSON] et al. [62] in metakaolin.