PSI - Issue 67

I. Flores-Vivián et al. / Procedia Structural Integrity 67 (2025) 80–89 Ismael Flores-Vivián/ Structural Integrity Procedia 00 (2024) 000 – 000

81

2

NaAlO 2 Sodium Aluminate

ZN

Natural Zeolite

H 2 O

Deionized Water

1. Introduction

Concrete is one of the most consumed building materials in the world, due to its versatility, durability and low cost (Juenger, M.C.G.; Winnefeld, F.; Provis, J.L.; Ideker, J.H., 2011). The manufacture of hydraulic concrete traditionally involves the use of CP, which is projected to reach a production of 4.8 GTon by 2050 (Schneider, Romer, Tschudin, & Bolio, 2011). This implies a high degree of pollution, as the production of CP has been shown to be one of a major source of carbon dioxide (CO 2 ) emissions. One Ton of CP produces 0.95 Ton of CO 2 (Davidovits, 2013). CP production, considering fuel consumption, contributes 8% of global CO 2 emissions (Olivier, Janssens-Maenhout, Muntean, & Peters, 2016). The reduction of the clinker has been a priority in the reduction of CO 2 emissions, which is why the partial substitution of clinker by other materials during the production of CP has been implemented, as well as the use of alternative cementitious materials (Schneider, Romer, Tschudin, & Bolio, 2011). One of these alternatives is alkali-activated cementitious materials, which have caused interest due to their high strength, durability and low environmental impact. It has been estimated that replacing CP with alkali-activated cementitious materials can reduce CO 2 emissions by more than 80% (Juenger, M.C.G.; Winnefeld, F.; Provis, J.L.; Ideker, J.H., 2011). Geopolymers are alkali-activated cementitious materials that have low calcium content in the system. They are obtained from the mixture of a solid precursor of aluminosilicates, an (AA) ( NaOH , potassium hydroxide, Na 2 SiO 3 , among others), and water (Davidovits, 2013). For the manufacture of geopolymers, MK, blast furnace slag, class F fly ash, among others, can be used as precursors (Juenger, M.C.G.; Winnefeld, F.; Provis, J.L.; Ideker, J.H., 2011) (Odler, 2000). Zeolites are aluminosilicate porous crystalline framework materials that are based on an infinite three dimensional lattice of AlO 4 and SiO 4 tetrahedra bonded together by sharing all oxygens (Smith, 1984). Given the strong similarities between the formation of geopolymers and the synthesis of zeolites, it is possible that zeolites may be obtained from the crystallization of the amorphous geopolymer gel, and the presence of faujasite in metakaolin based geopolymers has been confirmed (Yun-Ming, Cheng-Yong, Bakri, & Hussin, 2016) (Palomo, Blanco-Varela, Granizo, Puertas, Vazquez, & Grutzeck, 1999). This work focuses on studying the effects of the addition of NaY-type nanozeolite synthesized by the sol-gel method in metakaolin-based geopolymers. The cement will be evaluated to understand the properties of the geopolymer, such as density, compressive strength and setting time. The nano-reinforced geopolymer will be a new generation cement, which is environmentally friendly, resulting in an eco-friendly cement with high durability and high mechanical strength performs. 2. Experimental procedure The present work was carried out in three stages, the first was the selection and characterization of materials; followed by the synthesis of faujasite-type nanozeolite NaY synthesized from NaAlO 2 , Na 2 SiO 3 , and NaOH; and finally the manufacture of geopolymer pastes, which were made from a precursor of aluminosilicates, which in this case was MK, and an AA, which consists of a combination of NaOH and Na 2 SiO 3 . Three types of paste were manufactured, the reference geopolymer without additions, a geopolymer with a substitution of 0.5% natural zeolite and a geopolymer with a substitution of 0.5% of the synthesized zeolite. The pastes were evaluated and compared by microstructural characterization using SEM and FT-IR. 2.1. Materials For the synthesis of nanozeolite NaY, NaAlO 2 was used, with a composition of Al (Al 2 O 3 50-56%), Na (Na 2 O 37 45%), with a density of 2.60 g/cm 3 . The soluble Na 2 SiO 3 had a composition of 8.9% Na 2 O, 28.75% SiO 3 , SiO 2 /Na 2 O ratio = 3.23 (N grade), 37.65% of solids, 62.37% H 2 O and 1.39 g/cm 3 of density. The NaOH had a presentation of solid white color in the form of flakes with 98.80% NaOH content. Commercially available MK was used as a precursor for the geopolymer, with a density of 2.55 g/cm 3 and d 50 = 14.7 μ m . MK was analyzed by XRD, in order to observe the crystalline phases, as well as the amorphous halo characteristic of these pozzolans, which occurs at angles 15° to 35° in 2Ɵ, which can be seen in Figure 1 (Yun-Ming, Cheng-Yong, Bakri, & Hussin, 2016).