Geopolymers as Sustainable Material for Strengthening and Restoring Unreinforced Masonry Structures: A Review

Abstract

Unreinforced masonry (URM) structures are vulnerable to earthquakes; thus, materials and techniques for their strengthening and restoration should be developed. However, the materials used in some of the existing retrofitting technologies for URM and the waste produced at its end-of-life are unsustainable. The production of ordinary Portland cement (OPC) worldwide has enormously contributed to the global carbon footprint, resulting in persistent environmental problems. Replacing OPC with geopolymers, which are more sustainable and environmentally friendly, presents a potential solution to these problems. Geopolymers can replace the OPC component in engineering cementitious composites (ECC), recommended to strengthen and restore URM structures. In the present paper, the state-of-the-art knowledge development on applying geopolymers in URM structures is discussed. The discussion is focused on geopolymers and their components, material characterization, geopolymers as a strengthening and restoration material, and fiber-reinforced geopolymers and their application to URM structures. Based on this review, it was found that the mechanical properties of geopolymers are on par with that of OPC; however, there are few studies on the mentioned applications of geopolymers. The characterization of geopolymers’ mechanical and physical properties as a restoration material for URM structures is still limited. Therefore, other properties such as chemical interaction with the substrate, workability, thixotropic behavior, and aesthetic features of geopolymers need to be investigated for its wide application. The application method of geopolymer-based ECC as a strengthening material for a URM structure is by grouting injection. It is also worth recommending that other application techniques such as deep repointing, jacketing, and cement-plastering be explored.

Geopolymeric Composites Containing Industrial Waste Reinforced with Arundo donax Fibers

“…A different strategy concerns the use of completely alternative materials. Alkaliactivated materials or geopolymers can be considered valuable candidates for the substitution [6,7], in that they are derived from industrial or anthropogenic wastes [8][9][10][11] and they can be activated at room temperature, in the same way as the traditional mortars/concretes. Some wastes have been intensively studied, such as fly ash, blast furnace slags, bottom ash, silica fume or red mud.…”

Enhancing the Mechanical Properties of Historical Masonry Using Fiber-Reinforced Geopolymers

“…They are also lightweight and flexible, have excellent electrical and thermal insulation properties, and resist chemical attacks [ 10 , 11 , 12 ]. However, one area has not been much examined: cultural heritage preservation [ 13 , 14 ].…”

Effect of the Partial Replacement of Cement with Waste Granite Powder on the Properties of Fresh and Hardened Mortars for Masonry Applications

“…In cement mortars, it has been found to be possible to replace cement with various waste materials. Even a small replacement of cement with waste material can have a positive impact on the environment [8,9].…”