Лако-красочные материалы — производство

Design of Adhesive Mortars: Binders, Fillers and Aggregates

Binders of either lime (L: by CaO Hellas) with metakaolin (M: Metastar 501 by Imerys), or natural hydraulic lime (NHL: NHL3.5z by Lafarge), as well as nano-titanium dioxide (T: nano-structured nano-titania by NanoPhos), used as filler due to its photocatalytic activity, were employed for the design of the adhesive mortars. The already established improvement of hydration and carbonation process due to the photocatalytic activity of nano-titania in anatase form (Hyeon-Cheol 2010) added to cement mortars, was taken into consideration to assess whether the adhesion performance of the studied mortars was affected. Moreover, the self-cleaning properties of the adhesive mortars could also be attained due to the photocatalytic action of the nano — titania. XRD, FTIR and DTA-TG techniques were used to characterize the raw products.

Table 1 lists the mortar mixes; the ratio of water to binder (W/B) ranges from 0.8 to 0.6. The quantity of lime required to react with metakaolin was fixed in a weight ratio equal to 1.5, ensuring the pozzolanic reaction. Any unreacted quantity of lime, after its carbonation, provides plasticity to the end — product and enables the mortar to acquire a pore size distribution similar or compatible to porous stone, thus allowing a homogeneous distribution of water and water vapor in the complex system (Moropoulou 2005). Furthermore, this enhanced plasticity can function as a tool for the distribution and absorption of external stresses, which otherwise could lead to the mechanical failure of the mortar. TiO2 nano-powder dispersion in a small amount of water was achieved through ultrasonic treatment for 15 min; afterwards the obtained TiO2 colloidal solution was mixed with the other raw materials and the mixture was stirred with a handheld mixer for 5 min. Due to the fact that the fine aggregates can contribute to the avoidance of shrinkage and cracking during the setting process, the addition of sand with fine grains was deemed essential. Consequently, equal proportions of sand passing through the 125 and 63 pm sieves were added in the mix; these were previously washed with water to free any harmful soluble salts.

The above mixtures (Table 1) were molded in prismatic and cubic moulds, with dimensions of 4*4*16 cm and 5*5*5 cm, respectively and were then placed in a curing chamber for setting, at RH = 65 ± 3 % and T = 20 ±2 oC, according to the procedure described in the EN 196-1. The mechanical properties of the designed mortars were characterized by measuring their uniaxial compressive (Fc) and flexural (Ff-3pb) strengths, according to EN 1015-11:1999.