Reusing Geopolymer Waste from Matrices Based on Metakaolin or Fly Ash for the Manufacture of New Binder Geopolymeric Matrices

Abstract

The increasing use of geopolymer materials in the construction and civil engineering sectors generates a large amount of non-biodegradable waste that will end up in landfills. It is therefore necessary to anticipate solutions for the proper management of this waste. In this work, new geopolymer materials were fabricated by partially replacing the reactive raw minerals (fly ash, FA, or metakaolin, MK) with used geopolymers (fully fly ash-based, FAref, or metakaolin-based, MKref), in order to develop a strategy to reuse geopolymer waste. Their workability and setting behavior were studied in the fresh state, and the geopolymerization process was investigated by calorimetry and by electrochemistry. Mechanical properties and the ability for coating mineral aggregates were assessed, and the resulting adhesion properties were analyzed using matrix/sand mortars. It appears that the new geopolymer materials as well as the mortars are endowed with good performances. The compressive strengths are above 50 MPa and therefore meet the requirements of different construction materials. This demonstrates the recyclability of geopolymer materials. Moreover, an analysis of the influence of the substitution of recycled geopolymers on the setting and on the mechanical performances of mortars makes it possible to propose a binder-recycled geopolymer interaction model for the formation of new binding matrices.

Preparation of Cement Clinker from Geopolymer-Based Wastes

“…The preparation of geopolymer materials was carried out in accordance with our previous study [ 8 ]. The procedure for geopolymer preparation is shown in Figure 4 .…”

“…These studies generally remain within the framework of a single approach, which consists in reusing the waste in the form of aggregates to replace natural aggregates (sand or gravel) in order to produce mortars or concretes. Hattaf et al [ 8 ] proposed to reuse geopolymer waste as a substitute for the starting raw materials (metakaolin and fly ash) to produce new geopolymer matrices. These authors demonstrated that high compressive strengths can be maintained for substitution rates up to 40 wt% (compressive strengths greater than 43 MPa).…”

The Effect of Basalt Fiber on Mechanical, Microstructural, and High-Temperature Properties of Fly Ash-Based and Basalt Powder Waste-Filled Sustainable Geopolymer Mortar

“…The fine-grained waste material generated during processing is transported to and deposited in landfills. Therefore, geopolymer was produced using different waste materials, and its properties were investigated in previous studies [4][5][6][7]. The sodium hydroxide (SH) and sodium silicate (SS) used in this study were close to the amounts of SH and SS used in these studies.…”

Influence of the Integration of Geopolymer Wastes on the Characteristics of Binding Matrices Subjected to the Action of Temperature and Acid Environments

“…Few works dedicated to this theme have been identified in the literature [ 24 , 25 , 26 , 27 , 28 , 29 ]. In a recent study [ 24 ], we investigated the possibility of partially replacing fly-ash (FA) or metakaolin (MK) with Fly-ash-based Recycled Geopolymer (FARG) and Metakaolin-based Recycled Geopolymer (MKRG) wastes in order to manufacture new geopolymer matrices that consume less raw materials.…”

“…Few works dedicated to this theme have been identified in the literature [ 24 , 25 , 26 , 27 , 28 , 29 ]. In a recent study [ 24 ], we investigated the possibility of partially replacing fly-ash (FA) or metakaolin (MK) with Fly-ash-based Recycled Geopolymer (FARG) and Metakaolin-based Recycled Geopolymer (MKRG) wastes in order to manufacture new geopolymer matrices that consume less raw materials. Fine-grained powders of FARG and MKRG were used in the partial substitution of the sources of aluminosilicates FA and MK up to a mass rate of 50% to produce three formulations of binders referenced as FA/FARG, MK/MKRG and MK/FARG.…”