The mean mixing water is 17(4)% in weight, the smallest value corresponds to mortar HC with 14 %, and the highest to mortar HB with 27 %.
Mechanical properties at 90 days are shown in Table 3. The mean compressive strength at 90 days is 2.36(1.3)MPa; with a minimum of 0.68 MPa (mortar HSP) and maximum of 4.30 MPa (mortar HSG). These results are in the same range than those of some commercial mortars: compression strength at 90 days, Lithomex of 8.3–9.0 MPa; Conserv, 0.97 MPa, Altarpierre, 15.6 MPa (Torney et al.2014; Lopez-Arce et al 2016). In another experimental study, comparing 160 mortars values go from 0.5 MPa to 15.20 MPa with a mean value of 3.76 MPa (Apostolopoulou et al., 2019).
The HSG mortar has the strongest mechanical properties. This mortar was fabricated with waste glass powder and the obtained results are in accord with those of Carsana et al. (2014) and Edwards et al. (2007). The mean flexural strength at 90 days for all the mortars is 0.86(.22) MPa, with a minimum value for mortar HSP and AS. Considering that AS mortar was made with aerial lime this value is in accord with the work of Margalha et al. (2011). Mortar HSG shows the highest value with 1.29 MPa.
Table 3: Mechanical properties of mortars. CS: Compressive Strength (MPa) at 90 days; FS: Flexural Strength (MPa) at 90 days; E: Young modulus (GPa), υ: Poisson coefficient.
| Mortar | CS | FS | E | u |
| HFD | 2.04 (0.06) | 0.82 (0.25) | 6.3 (0.73) | 0.13 (0.04) |
| HSD | 1.76 (0.33) | 0.94 (0.18) | 6.43 (0.20) | 0.15 (0.05) |
| HS | 1.20 (0.05) | 0.77 (0.02) | 7.28 (0.37) | 0.21 (0.03) |
| HB | 1.91 (0.20) | 0.91 (.25) | 5.14 (0.71) | 0.18 (0.03) |
| HSCR | 3.51 (0.07) | 1.07 (0.01) | 8.91 (0.45) | 0.21 (0.01) |
| HSC | 3.63 (0.37) | 1.04 (0.04) | 10.12 (0.71) | 0.19 (0.07) |
| HSG | 4.3 (1.2) | 1.29 (0.15) | 11.45 (0.15) | 0.26 (0.02) |
| HSP | 0.68 (0.08) | 0.48 (0.04) | 2.58 (0.32) | 0.32 (0.01) |
| HC | 3.62 (0.50) | 0.82 (0.06) | 8.03 (0.90) | 0.17 (0.07) |
| AS | 1.01 (0.27) | 0.69 (0.08) | 6.29 (0.09) | 0.15 (0.01) |
63The use of organic additives, like resins, can improve the mechanical properties of mortars (Ordoñez et al. 2019). In our case, HSCR mortar shows only little improvement in the flexural strength compared to HSC mortar.
The mean dynamic Young’s modulus at 360 days is 7.25(2) GPa, the minimum is shown in mortar HSP with 2.58 GPa and the maximum in HSG with 11.45 GPa. These values are similar to those obtained by Nežerka et al. (2015).
The mean dynamic Poisson ratio at 360 days is 0.20(0.05), the minimum corresponds to mortar HSFD with 0.13, and the maximum to mortar HSP with 0.32. These values are similar to those of Palomar et al. (2015).
Frost Resistance results are presented in Figure 3. All mortar samples presented a slow and constant increase in weight during the thaw/frost test until the 13 cycles when the sample HFD started to lose weight. The mean mass variation per unit of mass is 0.11(0.04), with a maximum of 0.15 for the mortar HC. The mean final weight is 11(4)% higher than the initial one. This fact may indicate that mortars are still undergoing carbonation under these conditions, as carbonation produces a weight increase in mortars, clearly higher in mortars with higher amount of lime (Arizzi et al. 2012).
The results of salt crystallization tests are presented in figure 4. Weight decreases for all the samples during 16 cycles. Mortars AS and HSP collapse prematurely, with partial destruction at cycle 8. Mortar HSC shows the same partial destruction at cycle 13. In contrast, all the other mortars resist 16 cycles. In mortars HC, HB and HS, deterioration occurred at a much slower rate. These values are within normal boundaries according to Klisińska-Kopacza et al. (2013). Low weathering rate is related to the presence of hydraulic lime and hard minerals, such as silicates. Mineral additives can improve the durability of the mortars according to Theodoridou et al. (2014). The Mortar HSPR showed better durability in comparison with the mortar HSP. We can say that the addition of pinecone resin solution seems to be adequate to increase the durability of mortars.
Figure 3: Frost Resistance test. ΔM/M(%) vs number of cycles.
Figure 4: Salt Crystallization test. ΔM/M(%) vs number of cycles.
Conclusions
Correlations were established between mortars properties and the use of different additives. It can be concluded that employed recyclable additives will improve some mortars properties.
Pinecone fragments reduce significantly the capillarity coefficient but also its mechanical properties. The waste glass powder improves the compressive strength of materials and decreases porosity. Mortars with crushed brick waste as aggregate absorb almost twice more water than mortars with sand, this additive can be used as a red dye and has a high resistance in durability tests.
The Pinecone Resin shows an improvement in the durability of the mortars as well as a slight improvement in mechanical properties.
Future
