Influence of Activators on Mechanical Properties of Modified Fly Ash Based Geopolymer Mortars.

Piotr Prochon,Tomasz Piotrowski,Luc Courard,Frédéric Michel,Andrzej Garbacz,Zengfeng Zhao

doi:10.3390/ma13051033

Piotr Prochon, Tomasz Piotrowski + Show 4 more

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https://doi.org/10.3390/ma13051033

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Journal: Materials	Publication Date: Feb 25, 2020
Citations: 29	License type: CC BY 4.0

Affiliation: Warsaw University of Technology, University of Liège

Abstract

The aim of this work was to study the influence of the type of activator on the formulation of modified fly ash based geopolymer mortars. Geopolymer and alkali-activated materials (AAM) were made from fly ashes derived from coal and biomass combustion in thermal power plants. Basic activators (NaOH, CaO, and Na2SiO3) were mixed with fly ashes in order to develop binding properties other than those resulting from the use of Portland cement. The results showed that the mortars with 5 mol/dm3 of NaOH and 100 g of Na2SiO3 (N5-S22) gave a greater compressive strength than other mixes. The compressive strengths of analyzed fly ash mortars with activators N5-S22 and N5-C10 (5 mol/dm3 NaOH and 10% CaO) varied from 14.3 MPa to 5.9 MPa. The better properties of alkali-activated mortars with regular fly ash were influenced by a larger amount of amorphous silica and alumina phases. Scanning electron microscopy and calorimetry analysis provided a better understanding of the observed mechanisms.

Highlights

Ordinary Portland Cement (OPC), within its nearly two centuries of history, become an essential component of the built environment
Exhibits the chemical properties required in EN 450-1 and in ASTM C618 corresponding to Class F fly ash
The high level of Si and Al components is important in the geopolymerization process mainly because of their contribution to the strength development that occurs due to alkaline activation [43,44]

Summary

Introduction

Ordinary Portland Cement (OPC), within its nearly two centuries of history, become an essential component of the built environment. With increased awareness in the European Union of the greenhouse gases emission from the energy production and industrial processes, some mitigation strategies include diverse approaches such as consideration of an increase of the share of renewables in energy production, use of biomass fuels, an increase equipment efficiency, preparation of environmentally-friendly concrete composition, use of alternative raw materials, and use of material substitutes [7,8]. One of the possible paths for mitigating the CO2 emissions from OPC production and the problems associated with it is the development of a new type of alternative, sustainable material obtained from industrial wastes including the geopolymer [9,10].

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