Abstract
Ceramics tile wastes (CWs) were mechanically conditioned for the preparation of alkali-activated hybrid-cements from CW (90 wt.%) and Portland cement (10 wt.%) mixtures using sodium silicate (SS) + NaOH as alkaline activators. Molar ratios of SiO2/Al2O3 (6.3 to 7.7) and Na2O/SiO2 (0.07 to 0.16) were used. The cements were prepared at room temperature (25 °C) and characterized by mechanical and physical properties and microstructure. The optimized cement was used for the preparation of novel photoactivated composite materials by incorporating 5 and 10 wt.% TiO2 (Ti) and ZnO (Z) nanoparticles, and its self-cleaning and bactericidal properties were evaluated by means of the degradation of rhodamine-B (Rh-B) and the growth inhibition of Klebsiella pneumoniae and Pseudomonas aeruginosa bacteria. The results of this study showed that the 100SS-5Z and 50SS:50G-10Ti cements have an effective photocatalytic activity for Rh-B degradation of 98.4% and 76.4%, respectively, after 24 h. Additionally, the 100SS-5Z and 50SS:50G-10Ti cement pastes and their respective mortars were effective in inhibiting the growth of Pseudomonas Aeruginosa and Klebsiella pneumoniae bacterial strains, evidenced by the formation of bacterial inhibition halos around the sample discs. Finally, these results are novel, and open the possibility of using constructions and demolition tile waste in high proportions for the elaboration of new rendering mortar with innovative properties.
Highlights
It is known that the widespread use of ordinary Portland cement (OPC) in the construction industry has a high environmental impact
Coatings 2022, 11, x FOR PEER REVIEW Figure 1 shows the appearance of Ceramics tile wastes (CWs) before and after being mechanically proce6edoef d2.1 Initially, the CWs were collected and dried at room temperature (25 ◦C) for 24 h, and were mechanically processed by hammer milling followed by ball milling (2 h)
The presence of hybrid sodium calcium aluminosilicate hydrate (N-CASH) gel is identified and corroborates the results found by other authors [19,67,68,69]
Summary
It is known that the widespread use of ordinary Portland cement (OPC) in the construction industry has a high environmental impact. The different raw materials for the manufacture of alkali-activated cements include calcined clays, such as metakaolin [8]; fly ash [9]; blast furnace slag [10,11,12]; different agricultural byproducts, such as rice husk ash [13] and sugarcane bagasse [14]; and construction and demolition waste [15], such as concrete [16,17] and brick [18,19,20,21]. In the case of the alkaline activation of low calcium precursors, such as type F fly ash, and the use of a sodium alkaline activator, an amorphous sodium aluminosilicate hydrate (NASH) gel is obtained as the main reaction product [26]
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