The development of a geopolymer binder from the interbasaltic laterites of Northern Ireland

  • John McIntosh

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Over the last number of years, geopolymers and Alkali Activated Cementitious Materials (AACM) have been proposed as low carbon alternatives to Portland Cement, offering up to 80% reduction in CO¬2 emissions. Historically, geopolymer technology has focused on Ground Granulated Blastfurnace Slag (GGBS), Fly ASH (FA) or Metakaolin (MK) as primary raw materials or precursors. GGBS and FA are both by-products from other processes and as such have a limited longevity of supply. Pure MK is prohibitively expensive. These factors result in limitations being placed on the long-term sustainability of geopolymers.

However, impure clays containing kaolinite may be able to be used as precursors provided associated minerals do not affect the geopolymerisation process. Such clays are found in parts of Northern Ireland and have never been considered as precursors for a geopolymer system.

This thesis examines the composition of these lateritic clays using various analytical methods to determine their ability to form a geopolymer binder with a view to providing a case study which could be applied wherever similar clays are found globally. It was found that such clays could result in a geopolymer binder capable of producing mortars with compressive strengths of over 70 MPa. A selection method was proposed to guide others in the field on the selection of suitable clays. The effect of curing methods on the binder were explored and a model proposed to explain the differences between air cured and covered cured geopolymer mortars. This work enabled development of a fundamental understanding of the calcined clay geopolymer system through FTIR and SEM analysis. Finally, the scaling up of manufacturing of this new technology from lab scale to commercial production is presented. Influences of particle sizing, calciner type activator production, quality control measures and application development are presented.

This thesis has contributed to the body of research by bringing an idea regarding the use of locally available clays from initial research through to a point of production readiness and the offering of a real, low-carbon alternative to Portland cement. The work has also resulted in the development of a model showing presenting new information on the interfacial transition zone between relic metakaolin particles and the geopolymer matrix.
Date of AwardDec 2021
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsBanah UK Limited
SupervisorMarios Soutsos (Supervisor) & Sree Nanukuttan (Supervisor)

Keywords

  • Calcined clay
  • geopolymer
  • AACM
  • kaolinite
  • laterite
  • low carbon cement

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