Siegfried Siegesmund - Monument Future

Mortars were prepared in the laboratory at average temperature of 24 °C and relative humidity of 40 %. The preparation process consists in several steps: 1) sands were dried at 60 °C during 24 h, 2) weighing of the components, 3) dry mixing using an electric mixer (Rubimix 9), 4) addition of water and mechanical mixing for 3 minutes, 5) mortars are moulded in prismatic casts, 40 mm × 40 mm × 160 mm and placed in hermetic plastic boxes for 7 days to preserve 90 % humidity, 6) samples are unmoulded and put in a humidity chamber at 65 % for 21 days following the standard EN 1015-2. Finally, the samples were stored at laboratory conditions.

The different formulations obtained are presented in Table 1. To name the mortars we use the initials of the components: H for hydraulic lime, A for aerial lime, C for calcareous sand, S for silica sand, F for silico-calcareous sand, D for fine silica sand, 61G for waste glass powder, B for chamotte (crushed brick), P for pinecone and R for the resin of the pinecone.

Figure 1:Mortars samples at 180 days. The different formulations obtained are presented in Table 1.

The first mortar prepared was the HFD after evaluation it was decided to increase the amount of the binder, to increase the resistance of 20 %. The mortars HS and AS are performed to compare binders, the mortar HB is prepared to test the additive, the mortar HSD is prepared to test the effect of granulometry to increase de resistance.

The HSC and HSCR mortars start from the same base with 30 % of binder but one is prepared with water and the other with the pine resin solution, mortar HC was prepared to test the calcareous sand, and HSG for test the WPG.In future work more formulas will be prepared to make comparisons.

Several properties have been measured in the harden mortars (90 or 180 days old). Porosity and density have been measured by the triple weight method following the standard EN 1936. Compressive and flexural strength were obtained in 4 × 4 × 16 cm 3samples, according to EN 1015-11 standard. Capillarity water absorption tests were performed following the standard EN 1015-18. Durability of the samples was estimated by salt crystallisation and frost resistance tests following standards EN 12371 and EN 12370. Dynamic Young’s modulus (E) and Poisson’s coefficient (n) from P and S wave velocities using the next equations (Baron 2007):

In order to validate the obtained formulations, their physical properties have been compared with three commercial products (Altarpierre, Artopierre and Lithomex TM) previously studed in our laboratory and largely employed in France and others parts of the world.

Granulometry of the mortars produced in this work was compared to that of the commercial products to compare if it has an impact in the durability of the mortar. The particle diameter of all mortars ranges from 0.08 to 0.8 mm. Particle size distribution of mortar HB is a little different from the others due to the use of chamotte as aggregate. Mortar AS shows smaller particle size due to the use of air lime.

Porosity and density, water capillarity absorption and relative amount of mixing water necessary to obtain the expected workability are presented in Table 2. The mean density measured at 90 days is 1,720(109) kg/m³, HSP mortar presents the smallest value with 1534 kg/m³ and the highest value corresponds to mortar HSG with 1,873 kg/m³. These two mortars have additives, pinecone and waste glass powder respectively, which shows that the use of the correct additives is able to modify 62the density of a restoration mortar. The mean porosity at 90 days is 33.7(4) %; HSG mortar, with 29.4 %, presents the lowest value and the highest value corresponds to HSP mortar, with 40.9 %. As expected, mortar with the lowest density has the highest porosity.

Table 1:Restoration mortar formulations in weigh percentage. WGP: Waste glass powder, PN: Pine cone, PCRS (Pine Cone Resin Solution), CHAM:Chamotte (Crushed brick waste).

Figure 2:Granulometric Curves.

The mean capillarity coefficient at 180 days is 1.73(0.53) kg/m²min ½, with a minimum of 0.99 kg/ m²min ½for mortar HSP and a maximum of 2.57 Kg/ m²min ½for mortar HB. These results are in accord with the results obtained by Margalha et al. (2011) in mortars with hot lime mix.

Table 2:Physical characteristics of mortars. ρ: density (kg/m³), n: open porosity (%), C: Capillarity coefficient (Kg/m²min ½), W: mixing water (g water/g dry mortar).

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.