Читать книгу Monument Future - Siegfried Siegesmund - Страница 76

The amount of raw materials is limited and must be preserved and managed with caution. One important aspect of the presented work is to save natural raw materials when formulating restauration mortars. In order to increase the sustainability of the restoration mortar industry, the use of waste materials will be enhanced.

Different mixtures were prepared in order to determine the influence of components in the physical properties of harder mortars. Two binders, four types of sand (aggregates) and four additives were employed in the fabrication of studied mortars. The binders are: aerial lime (Cl90) and hydraulic lime (NHL5) both provided by Socli company. The aggregates are: silica sand (Leroy Merlin), calcareous sand provided by Rocamat company, silico-calcareous sand (Italcementi group) and fine silica sand (Sibelco). Four different additives were used: chamotte provided by Briqueterie d’Allone, ground glass provided by the Fédération du Verre, ground pine cone and water/oil solution of pine cone.

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 cm³ samples, 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.