Preparation and characterization of a composite material based on a geopolymer binder and quartzite aggregates

We have developed a geopolymer material by alkaline reaction on thermally activated kaolin. Initially we characterized the geopolymer by different methods (rheology, DTA-TGA, etc.) and we mixed it with different amounts of natural sand to obtain a granular composite. The structural characterization of this material was undertaken by several techniques (XRF, XRD and microscopic observations). A rheological study was implemented to determine the influence of the aggregate rate on the setting kinetic. Three-point bending and compression tests were conducted for mechanical characterization. We also conducted microindentation tests to study the influence of quartzite rate on the hardness of the material. The results indicate that the integration of quartzite (up to 15 wt. %) did not alter the setting kinetic. We noted a small degradation of the mechanical behavior when the quartzite rate is increased; this effect is due to a higher density of microcracks. However, adding the aggregate has a beneficial effect on the hardness of the material. These attractive features make this material a plausible matrix whose reinforcement with plant fibers will provide a ternary composite suitable for multiple applications

Relationship between phosphate structure and acid-base properties of phosphate-modified zirconia—Application to alcohol dehydration

International audienc

Influence of phosphate structure on acid-base properties of phosphate-modified zirconia

International audienc

Fusion of phosphate by-products and glass waste for preparation of alkali-activated binders

Landfilling of mine and industrial waste streams leads to environmental and economic issues. Sustainable management methods through valorization in manufacturing green construction materials are a current research interest. Here, a promising process for recycling mine tailings, such as phosphate sludge, is proposed. A mixture of phosphate sludge, kaolin clay (Al source), and glass waste (Si source) was prepared. Three fluxing agents were tested at 1000 °C (NaOH, NaCO, NaSO). NaCO was selected as the most cost-effective. The precursors were alkaline activated with NaOH solution (2, 6, and 8 M). At 28 days of curing (20 h room temperature + 6 h 85 °C + room temperature), the best compressive strength (of more than 45 MPa) was obtained with 8 M NaOH. The reaction products, characterized by XRD, FTIR, SEM, and MAS NMR, show that the main reaction products is a gel N–A–S–H/(N,C)–A–S–H together with some unreacted crystalline phases formed during the fusion

Properties of metakaolin based geopolymer incorporating calcium carbonate

International audienceAn alkaline solution, thermally activated kaolinite clay and a mineral additive (calcium carbonate) were mixed with the aim to elaborate a geopolymer material with physical and mechanical properties comparable to those of classical construction materials. The starting reagents were characterized by quantitative chemical analyses (XRF), mineralogical analyses (XRD), thermal gravimetric analyses (TGA), and grain size distribution measurements. The setting of the mixture (polymerization) was implemented by measuring the evolution of the viscosity as a function of time at different temperatures. The geopolymers were synthesized at a temperature of 40 degrees C. The investigation of the mechanical behavior reveals that these materials display acceptable characteristics the flexural and compression strength are around 4.6 and 26 MPa respectively, for an added calcium carbonate over dry matter ration up to 12% by weight. The promising results exposed in this paper show that the geopolymer formulations can be adapted for applications in construction and civil engineering structures as an alternative to conventional materials. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

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

International audienceThe 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

Properties of metakaolin based geopolymer incorporating calcium carbonate

International audienceAn alkaline solution, thermally activated kaolinite clay and a mineral additive (calcium carbonate) were mixed with the aim to elaborate a geopolymer material with physical and mechanical properties comparable to those of classical construction materials. The starting reagents were characterized by quantitative chemical analyses (XRF), mineralogical analyses (XRD), thermal gravimetric analyses (TGA), and grain size distribution measurements. The setting of the mixture (polymerization) was implemented by measuring the evolution of the viscosity as a function of time at different temperatures. The geopolymers were synthesized at a temperature of 40 degrees C. The investigation of the mechanical behavior reveals that these materials display acceptable characteristics the flexural and compression strength are around 4.6 and 26 MPa respectively, for an added calcium carbonate over dry matter ration up to 12% by weight. The promising results exposed in this paper show that the geopolymer formulations can be adapted for applications in construction and civil engineering structures as an alternative to conventional materials. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

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

International audienceThe 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